Chapter 3 - Routing Protocol Characteristics, EIGRP, and IS-IS Flashcards
1
Q
What is the default metric for any interface for the IS-IS routing protocol?
- 5
- 10
- 70
- 100
A
B.
The default metric for interfaces for IS-IS is 10.
2
Q
Which type of routers are used to interconnect areas in IS-IS?
- Level 1 routers
- Level 2 routers
- Level 1/2 routers
- Level 2 routers and Level 1/2 routers
A
D.
Both Level 2 and Level 1/2 routers are used to interconnect IS-IS areas.
3
Q
Which routing protocol is a distance-vector and classless protocol?
- RIPv2
- EIGRP
- OSPF
- IS-IS
A
A.
RIPv2 is a classless distance-vector routing protocol.
4
Q
Which type of routing protocol sends periodic routing updates?
- Static
- Distance-vector
- Link-state
- Hierarchical
A
B.
Distance-vector routing protocols send periodic updates.
5
Q
Which routing protocol has a default metric of 10?
- OSPFv2
- IS-IS
- EIGRP
- BGPv4
A
B.
In IS-IS, every interface has a default metric of 10.
6
Q
Which of the following is true regarding routing metrics?
- If the metric is bandwidth, the path with the lowest bandwidth is selected.
- If the metric is bandwidth, the path with the highest bandwidth is selected.
- If the metric is bandwidth, the highest sum of the bandwidth is used to calculate the highest cost.
- If the metric is cost, the path with the highest cost is selected.
A
B.
If bandwidth is used, the path with the highest bandwidth is selected. If cost is used, the path with the lowest cost is selected.
7
Q
Both OSPF and EIGRP are enabled on a router with default values. Both protocols have a route to a destination network in their databases. Which route is entered into the routing table?
- The OSPF route is entered.
- The EIGRP route is entered.
- Both routes are entered with load balancing.
- Neither route is entered; an error has occurred.
A
B.
OSPF has an administrative distance of 110. EIGRP has an administrative distance of 90. The route with the lower administrative distance is selected: EIGRP.
8
Q
Which is a route that satisfies the feasibility condition and is installed as a backup route?
- The successor
- The feasible successor
- The reported successor
- The backup successor
A
B.
The feasible successor satisfies the feasibility condition and is maintained as a backup route.
9
Q
Which parameters are included in the computation of the EIGRP composite metric that is used by default?
- Bandwidth and load
- Bandwidth and delay
- Bandwidth and reliability
- Bandwidth and maximum transmission unit (MTU)
A
B.
The default metrics for EIGRP are bandwidth and delay.
10
Q
Which routing protocol implements the Diffusing Update Algorithm (DUAL)?
- IS-IS
- IGRP
- EIGRP
- OSPF
A
C.
EIGRP implements DUAL.
11
Q
What is ES and IS in IS-IS?
A
ES = Endpoint System (hosts)
IS = Intermediate System (Routers - switches - etc)
12
Q
What are the following communication levels?
L0
L1
L2
L3
A
L0 - L0 (host) to L1 device communication
L1 - L1 to L1 intra-area communication within a single entity
L2 - L1 to L1 inter-area communication (different areas within same entity)
L3 - comms between different entities, beyond inter-area comms in a single entity.
Note: Cisco devices only operate on L1 and L2.
13
Q
Which area is mandatory in IS-IS? (Like Area 0 in OSPF)
A
none.
There are not mandatory areas in IS-IS. There is no need for a ‘backbone’ area in IS-IS.
However it is a best practice to use a ‘transit fabric’ or ‘transit area’ to move that traffic from area to area. This area needs to be a L2 area.
14
Q
The commands:
router isis
is-type level 1
Will allow adjacencies to form provide which two conditions are met?
A
The two conditions that must be met for an adjacency to form are: L1 to L1 routers and in the same area.
15
Q
What does the ‘net’ command stand for and what does it do in IS-IS?
A
The net command defines the NET = Network Entity Title
There is a lot of info in the net. These are 8-20 bytes long.
49.0001.0000.0000.0001.00
AFI.area-id.some-unique-identifier-like-MAC.00
AFI = first byte = Address Family Identifier, (49 => ISIS)
area-id = 0001
unique identifier = 1 (ususally this is the MAC address, but can be anything)
00 = NSEL or N-Selector, always zero for ISIS.
16
Q
T/F: IS-IS can form router adjacencies at layer 2, without IP addresses.
A
True.
17
Q
What is an LSP?
A
Link State packet.
IS-IS uses these L2 packets to exchange info to form adjacencies.
18
Q
What is the metric for every Cisco interface with respect to IS-IS?
A
10.
Every link has a metric of 10.
19
Q
What is the command ‘metric-style wide’ used for?
A
This allows the IS-IS system to bypass the default limit of hops.
This is best-practice.
20
Q
T/F: Security in IS-IS at three different levels.
A
True.
INTERFACE LEVEL:
At the interface level use this command:
R1(config)# router isis
R1(config-router)# isis password your_secret_password
and on the neighbor router, do the same.
AREA LEVEL:
This can be done at the area level as well, with this command:
R1(config)# router isis
R1(config-router)# area-password password
DOMAIN LEVEL:
This can be done at the domain level under the ‘router isis’ config.
R1(config)# router isis
R1(config-router)#domain-password password
21
Q
T/F: Adjacencies can be password protected, as in the neighborship will not form unless the password is used.
A
True.
INTERFACE LEVEL:
At the interface level use this command:
R1(config)# router isis
R1(config-router)# isis password your_secret_password
and on the neighbor router, do the same.
AREA LEVEL:
This can be done at the area level as well, with this command:
R1(config)# router isis
R1(config-router)# area-password password
DOMAIN LEVEL:
This can be done at the domain level under the ‘router isis’ config.
R1(config)# router isis
R1(config-router)#domain-password password
22
Q
What does the ATT bit advertise to the the routers that receive it from an IS-IS router?
A
This comes from a L1-L2 router and says “ I am your exit point.” , like a default route.
23
Q
What does RTP stand for with respect to EIGRP?
A
Reliable Transport Protocol
224.0.0.10 is the multicast address that EIGRP sends updates to using RTP, Hellos use this address for instance.
Sequence numbers are used by RTP to track what has been sent and received.
24
Q
How often does EIGRP send hello packets?
A
every 5 seconds for LAN links
every 60 seconds for WAN or really slow links
25
What is "dead interval" or "hold timer" in EIGRP?
Three times the hello period is the time it take for a route to be removed if the hellos have not been seen. The route is considered to be non-functional.
26
How many metrics are used in EIGRP? What are they?
The K values are:
1. Bandwidth
2. Delay
3. Load
4. Reliablity
5. MTU
Bandwidth and Delay are the most important, by far.
**Lowest Bandwidth** and **sum of delays** are used on a path to calculate the metric.
27
T/F: When EIGRP advertises a metric it includes the delay of the egress interface.
False. It sends a delay from it's perspective, as in looking out from the router towards the destination. This does not include the egress interface delay.
28
T/F: The command "sh eigrp topology" will show the FD.
true.
FD, Active and Passive routes, successor routes too.
29
What is the FD in EIGRP?
The Feasible Distance is the lowest cost, the metric itself, of the best route to get to a destination.
30
What is a sucessor?
The advertising router for the best route, the route with the best FD, is the sucessor.
31
T/F: When EIGRP receives two equal RD, Reported Distances, then it will install both routes into the table and perform equal cost load balancing.
True EIGRP does this by default.
Note: The RD is also known as the AD, Advertised Distance.
Note: The FD is the best RD.
32
What is the best metric to change in EIGRP to influence a route manually?
delay.
33
What is the feasibility condition used for?
This is a route loop prevention mechanism.
* The lowest FD is selected as the successor router. This router has the route that has the best metric, and definitely closer than we are.
* The second lowest FD is the "feasible successor", or backup router. This backup router has the route that is still closer to the destination than we are.
34
T/F: AS boundaries are query domain boundaries.
True.
When a route goes down, queries are sent out to every other router asking how to get to the missing route. The limits of these messages is bounded by the AS.
35
What is the AD of internal and external routes in EIGRP?
90 and 170.
Administrative distance is much greater for an external AS, or routes that are redistributed from other routing protocols.
36
T/F: Stub routers do not participate in queries for alternative routes.
True.
This is one of the main advantages of stub domains.
For instance, a branch office participates in sending and receiving routes, of course. But when a route goes down in the main network we do not want the branch office to be queried for alternative routes. That could lead to circuitous routes that are not efficient, routing tons of traffic through a little branch router. Bad things follow...
37
T/F: A stub router will not advertise a route that it has learned from another EIGRP router.
True!
This is very important. Stubs should not advertise routes they have learned, they will never be the optimal path.
By default a stub router can only advertise it's directly connected routes or a summary of them.
The command "eigrp stub" will create a stub network.
38
T/F: Making an interface passive will still advertise the directly connected route but the interface will not form an adjancy with other routers.
True. Here is an example of why...
Above we have two routers, R1 and R2. On the left side there’s the 192.168.10.0 /24 network with a switch and some computers. R1 wants to advertise this network to R2 but since there are no other EIGRP routers in the 192.168.10.0 /24 network, it’s pointless to send EIGRP hello packets on the FastEthernet 0/1 interface.
It’s also a security risk, when someone connects a router in the 192.168.10.0 /24 network (or starts a virtual router on their computer) they will be able to become EIGRP neighbors with R1.
To prevent this from happening, we will use the **passive-interface** command. **This will ensure that the network is advertised in EIGRP but it will disable hello packets on the interface.**
39
What are the differences between configuring authentication for eigrp between classic and named mode?
**Classic mode: (auth is set on interface and limited to md5)**
int eth0/0
ip authentication mode eigrp 10 md5
**Named mode:**
R1(config)# router eigrp ENSLD
R1(config-router)# address-family ipv4 unicast autonomous-system 10
R1(config-router-af)# af-interface eth 0/0
R1(config-router-af-interface)# authentication mode hmac-sha-256
40
T/F: The command "upgrade-cli" under the eigrp context will change your classic instance to a named mode.
True.
41
T/F: Distance-vector algorithms call for each router to send its entire routing table to only its immediate neighbors.
True.
42
RIPng can send triggered updates—that is, full routing table updates sent before the update timer has expired.
True.
However, this means that a router can receive a routing table with 500 routes with only one route change, which creates serious overhead on the network ( drawback).
43
T/F: EIGRP does not send periodic updates as other distance-vector routing protocols do.
True.
EIGRP is a hybrid routing protocol. It is a distance-vector protocol that implements some link-state routing protocol characteristics. Although EIGRP uses distance-vector metrics, it sends partial updates and maintains neighbor state information just as link-state protocols do.
EIGRP does not send periodic updates as other distance-vector routing protocols do.
44
T/F: After the initial exchange of information, link-state updates are not sent unless a change in the topology occurs.
True.
After the initial exchange of information, link-state updates are not sent unless a change in the topology occurs. Routers do send small hello messages between neighbors to maintain neighbor relationships. If no updates have been sent, the link-state route database is refreshed after 30 minutes.
45
Which routing protocols use more network bandwidth? Which use more CPU and memory?
When choosing a routing protocol, consider that distance-vector routing protocols use more network bandwidth than link-state protocols. Distance-vector protocols generate more bandwidth overhead because of the large periodic routing updates.
Link-state routing protocols do not generate significant routing update overhead but do use more router CPU and memory resources than distance-vector protocols. This occurs because with link-state routing protocols (generally speaking), WAN bandwidth is a more expensive resource than router CPU and memory in modern devices.
46
Which routing protocol, DV or Link State,
1. has better scalability?
2. converges faster?
3. has less routing overhead?
4. is easier to implement?
1. LS
2. LS
3. LS
4. DV
47
T/F: OSPF and IS-IS are hierarchical routing protocols.
True.
48
What type of routing protocol is EIGRP by default? flat or hierarchical?
**By default, EIGRP is a flat routing protocol**, but it can be configured with manual summarization to support hierarchical designs.
Flat routing protocols do not allow a hierarchical network organization. They propagate all routing information throughout the network without dividing or summarizing large networks into smaller areas.
Carefully designing network addressing to naturally support aggregation within routing-protocol advertisements can provide many of the benefits offered by hierarchical routing protocols. Every router is a peer of every other router in flat routing protocols; no router has a special role in the internetwork. EIGRP, RIPv1, and RIPv2 are flat routing protocols.
49
T/F: Classful routing protocols do not advertise subnet masks in their routing updates.
True.
Classful routing protocols do not advertise subnet masks in their routing updates; therefore, the configured subnet mask for the IP network must be the same throughout the entire internetwork. Furthermore, the subnets must, for all practical purposes, be contiguous within the larger internetwork.
For example, if you use a classful routing protocol for network 200.170.0.0, you must use the chosen mask (such as 255.255.255.0) on all router interfaces using the 200.170.0.0 network. You must configure serial links with only two hosts and LANs with tens or hundreds of devices with the same mask, 255.255.255.0. The big disadvantage of classful routing protocols is that the network designer cannot take advantage of address summarization across networks (CIDR) or allocation of smaller or larger subnets within an IP network (VLSM).
50
T/F: None of the IPv4 routing protocols support IPv6 networks, and none of the IPv6 routing protocols are backward compatible with IPv4 networks.
True.
But both protocols can coexist on the same network, each with its own routing protocol. Devices with dual stacks recognize which protocol is being used by the IP Version field in the IP header.
51
T/F: If two or more routing protocols offer the same route (with the same prefix length) for inclusion in the routing table, the Cisco IOS router selects the route with the lowest administrative distance.
True.
See attached table of AD values.
52
T/F:
Cost is the metric used by OSPF and IS-IS.
True.
53
T/F: In OSPF on a Cisco router, a link’s default cost is derived from the interface’s bandwidth.
True.
_The formula to calculate cost in OSPF is:_
**10^8/BW** where BW is the interface’s default or configured bandwidth.
For 10 Mbps Ethernet, cost is calculated as follows: BW = 10 Mbps = 10 × 10^6 = 10,000,000 = 10^7
cost (10M Ethernet) = 10^8/10^7 = 10
54
Cisco’s implementation of IS-IS assigns a default cost of ____ to all interfaces.
10
55
In OSPF, the sum of all the _______ to reach a destination is the metric for that route.
The sum of all the **costs** to reach a destination is the metric for that route.
The lowest cost is the preferred path.
56
The _____ parameter refers to the degree to which the interface link is busy.
The **load** parameter refers to the degree to which the interface link is busy.
A router keeps track of interface utilization; routing protocols can use this metric when calculating the best route. Load is one of the five parameters included in the definition of the EIGRP metric.
57
By default, ______ is not used to calculate the composite metric
By default, **load** is not used to calculate the composite metric.
If you have 512 kbps and 256 kbps links to reach a destination, but the 512 kbps circuit is 99% busy and the 256 kbps circuit is only 5% busy, the 256 kbps link is the preferred path. On Cisco routers, the percentage of load is shown as a fraction over 255.
58
What does 'load 255/255" on an interface indicate?
Utilization at 100% is shown as 255/255, and utilization at 0% is shown as 0/255.
59
The _____ parameter refers to how long it takes to move a packet to the destination.
The **delay** parameter refers to how long it takes to move a packet to the destination.
Delay depends on many factors, such as link bandwidth, utilization, port queues, and physical distance traveled.
60
T/F: Total delay is one of the five parameters included in the definition of the EIGRP composite metric.
True.
Total delay is one of the five parameters included in the definition of the EIGRP composite metric. By default, it is used to calculate the composite metric.
You can configure an interface’s delay with the *delay tens-of-microseconds* command, where tens-of-microseconds specifies the delay, in tens of microseconds, for an interface or network segment.
The interface delay can be checked with the *show interface* command. In Example 3-2, the interface’s delay is 20,000 microseconds.
61
What parameter measures the dependability of a network link?
The reliability parameter is the dependability of a network link.
Some WAN links tend to go up and down throughout the day. These links get a small reliability rating. Reliability is measured by factors such as a link’s expected received keepalives and the number of packet drops and interface resets.
If the ratio is high, the line is reliable. **The best rating is 255/255**, which is 100% reliability. Reliability is one of the five parameters included in the definition of the EIGRP metric. By default, it is not used to calculate the composite metric.
62
T/F: The MTU parameter is the maximum size of bits a unit can have on an interface.
False.
The MTU parameter is the maximum size of **bytes** a unit can have on an interface.
If the outgoing packet is larger than the MTU, the IP protocol might need to fragment it. If a packet larger than the MTU has the Do Not Fragment flag set, the packet is dropped.
As shown in Example 3-4, you can verify an interface’s MTU by using the show interface command.
63
What is Split Horizon?
Split horizon is a technique used by distance-vector routing protocols to prevent routing loops. Routes that are learned from a neighboring router are not sent back to that neighboring router, thus suppressing the route. If the neighbor is already closer to the destination, it already has a better path.
In Figure 3-6, Routers 1, 2, and 3 learn about Networks A, B, C, and D. Router 2 learns about Network A from Router 1 and also has Networks B and C in its routing table. Router 3 advertises Network D to Router 2. Now, Router 2 knows about all networks. Router 2 sends its routing table to Router 3 without the route for Network D because it learned that route from Router 3.
64
What is Poison Reverse?
Poison reverse is a route update sent out an interface with an infinite metric for routes learned (received) from the same interface. Poison reverse simply indicates that the learned route is unreachable. It is more reliable than split horizon alone.
Examine Figure 3-7. Instead of suppressing the route for Network D, Router 2 sends that route in the routing table marked as unreachable. In RIP, the poison-reverse route is marked with a metric of 16 (infinite) to prevent that path from being used.
65
What is counting to infinity?
Some routing protocols keep track of router hops as a packet travels through the network. In large networks where a routing loop might be present because of a network outage, routers might forward a packet without it reaching its destination. Counting to infinity is a loop-prevention technique in which the router discards a packet when it reaches a maximum limit. It assumes that the network diameter is smaller than the maximum allowed hops. RIP has a maximum of 16 hops, and EIGRP has a maximum of 100 hops by default. Maximum values are considered infinity.
66
T/F: EIGRP sends routing updates periodically, every 90 seconds.
EIGRP does not send routing updates periodically,
67
Where does EIGRP autosummarize networks, at what points in the network?
EIGRP autosummarizes networks at network borders.
68
T/F: EIGRP can load share over unequal-cost paths.
True. EIGRP can load share over unequal-cost paths.
69
What protocol number do EIGRP packets use?
Packets using EIGRP use IP number 88.
70
T/F: EIGRP advertises its routing table to its neighbors as link-state protocols do, but it uses hellos and forms neighbor relationships as distance-vector protocols do.
False.EIGRP advertises its routing table to its neighbors as **distance-vector** protocols do, but it uses hellos and forms neighbor relationships as **link-state** protocols do.
71
When does EIGRP send a partial update? Does it send full routing table updates periodically?
EIGRP sends partial updates **when a metric or the topology changes on the network.**
It does not send full routing table updates in periodic fashion as do distance-vector protocols.
72
What mechanism does EIGRP use to create loop-free paths?
EIGRP uses Diffusing Update Algorithm (DUAL) to determine loop-free paths to destinations.
73
What command is needed to configure un-equal cost load balancing in EIGRP
By default, EIGRP load balances traffic if several paths have an equal cost to the destination.
EIGRP performs unequal-cost load sharing if you configure it with the ***variance* *n*** command.
EIGRP includes routes that are equal to or **less than *n* times the minimum metric route** to a destination.
74
EIGRP internal routes have an administrative distance of \_\_\_\_. EIGRP summary routes have an administrative distance of \_\_\_\_, and EIGRP external routes (from redistribution) have an administrative distance of \_\_\_\_.
EIGRP internal routes have an administrative distance of **90**. EIGRP summary routes have an administrative distance of **5,** and EIGRP external routes (from redistribution) have an administrative distance of **170**.
75
EIGRP neighbors exchange the entire routing table when \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
EIGRP neighbors exchange the entire routing table when forming an adjacency.
76
EIGRP multicasts hello packets to (this IP address) _________ every _____ seconds on most interfaces.
EIGRP multicasts hello packets to **224.0.0.10** every **5** seconds on most interfaces.
77
In EIGRP, hello/holdtime timers are \_\_/\_\_\_ seconds for high-speed links and \_\_/\_\_\_ seconds for low-speed links.
In EIGRP, hello/holdtime timers are 5/15 seconds for high-speed links and 60/180 seconds for low-speed links.
EIGRP multicasts hellos every 60 seconds on multipoint WAN interfaces (that is, X.25, Frame Relay, ATM) with speeds less than a T1 (1.544 Mbps), inclusive. The neighbor holdtime is 180 seconds on these types of interfaces. To summarize, hello/holdtime timers are 5/15 seconds for high-speed links and 60/180 seconds for low-speed links.
78
T/F: RTP, EIGRP uses the Real Time Protocol to ensure timely delivery of messages in EIGRP.
False.
EIGRP uses Reliable Transport Protocol, RTP, to manage EIGRP packets.
**RTP ensures the reliable delivery of route updates and uses sequence numbers to ensure ordered delivery.** It sends update packets using multicast address 224.0.0.10. It acknowledges updates using unicast hello packets with no data.
79
Fact: DUAL selects a best path and a second-best path to reach a destination.
The best path selected by DUAL is called the \_\_\_\_\_\_\_\_\_\_, and the second-best path (if available) is the \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
DUAL selects a best path and a second-best path to reach a destination.
The *successor route* is the route with the lowest path metric to reach a destination.
The successor is the first next-hop router for the successor route. The best path selected by DUAL is the **successor**, and the second-best path (if available) is the f**easible successor**.
80
Fact: The feasible successor is a route that satisfies the feasibility condition and is maintained as a backup route.
What is the *Feasibility Condition*?
Feasibility Condition requires that the **RD \< FD.**
**RD:** The reported distance is the distance reported by a route to reach a prefix. (distance as it appears to the advertising neighbor)
**FD:** The feasible distance is the lowest calculated metric of a path to reach the destination. (NOTE: distance as it appears to THIS router. this includes the metric to reach the adversing neighbor)
A **feasibility condition** exists for a route to be considered a backup route where the RD received for that route must be less than the FD calculated on the local router.
81
If a successor route goes down, and the feasible successor becomes the new route, does the route go into an Active state?
A destination is in passive state when the router is not performing recomputations for the entry.
If the successor goes down and the route entry has feasible successors, the router does not need to perform recomputations and does not go into active state.
The FS is simply promoted to S.
82
What is SIA?
**Stuck In Active.**
DUAL places the route entry for a destination into active state if the successor goes down and there are no feasible successors.
EIGRP routers send query packets to neighboring routers to find a feasible successor to the destination. A neighboring router can send a reply packet that indicates it has a feasible successor or a query packet. The query packet indicates that the neighboring router does not have a feasible successor and will participate in the recomputation.
**A route does not return to passive state until it has received a reply packet from each neighboring router. If the router does not receive all the replies before the “active-time” timer expires, DUAL declares the route as stuck in active (SIA).**
The default active timer is 3 minutes.
83
EIGRP uses five packet types. What are they?
1. **Hello:** EIGRP uses hello packets in the discovery of neighbors.
2. **Acknowledgment**: An acknowledgment packet acknowledges the receipt of an update packet.
3. **Update:** Update packets contain routing information for destinations.
4. **Query:** EIGRP sends query packets to find feasible successors to a destination.
5. **Reply:** EIGRP sends reply packets to respond to query packets.
84
An acknowledgment packet acknowledges the receipt of an _________ packet. It is a _____ packet with no data. EIGRP sends acknowledgment packets to the _______ address of the sender of the update packet.
An acknowledgment packet acknowledges the receipt of an **update** packet. It is a **hello** packet with no data. EIGRP sends acknowledgment packets to the **unicast** address of the sender of the update packet.
85
EIGRP usually sends updates packets to the multicast address \_\_\_\_\_\_\_\_\_\_.
To which neighbors does EIGRP send unicast update packets?
EIGRP usually multicasts update packets to **224.0.0.10** when a link or metric changes. Update packets are acknowledged to ensure reliable transmission.
EIGRP unicasts update packets to **newly discovered neighbors.**
86
EIGRP sends reply packets to respond to ______ packets. Reply packets provide a ________ \_\_\_\_\_\_\_ to the sender of the query. Reply packets are unicast to the sender of the ______ packet.
EIGRP sends reply packets to respond to **query** packets. Reply packets provide a **feasible successor** to the sender of the query. Reply packets are unicast to the sender of the **query** packet.
87
EIGRP is not limited to ___ hops as RIP is; therefore, the network diameter can exceed this limit. In fact, the EIGRP diameter can be ____ hops. The default diameter is \_\_\_\_.
EIGRP is not limited to **16** hops as RIP is; therefore, the network diameter can exceed this limit. In fact, the EIGRP diameter can be **225** hops. The default diameter is **100**.
88
T/F: Stub routers are used to reduce EIGRP query traffic between hub routers and remote branch routers that are connected over WAN links.
True.
EIGRP stub routing conserves memory and CPU resources and improves network stability.
89
When the stub routing feature is enabled on the spoke router, the router only advertises specified routes to the hub router. The router does not advertise routes received from other EIGRP neighbors to the hub router.
The only disadvantage is that the stub router cannot be used as a ________ \_\_\_\_\_\_\_\_ between two hub sites.
When the stub routing feature is enabled on the spoke router, the router only advertises specified routes to the hub router. The router does not advertise routes received from other EIGRP neighbors to the hub router.
The only disadvantage is that the stub router cannot be used as a **backup** **path** between two hub sites.
90
Figure 3-9 shows an example of EIGRP stub router operation. If the LAN 10.10.10.0/24 goes down, where are the query packets sent?
Normally the Hub1 router would send query packets everywhere; however, there is no need to send query packets to stub branches because there are no alternate routes there.
**Once you configure the branch routers as EIGRP stub routers, the query is sent only to the Hub2 router.**
91
There are a few options when configuring the EIGRP stub routers. What do these options do?
**Receive-only:**
**Connected:**
**Static:**
**Summary:**
**Redistribute**:
There are a few options when configuring the EIGRP stub routers:
**Receive-only:** The stub router does not advertise network.
**Connected:** The stub router can advertise directly connected networks.
**Static:** The stub router can advertise static routes.
**Summary:** The stub router can advertise summary routes.
**Redistribute**: The stub router can advertise redistributed routes.
92
EIGRP allows unequal-cost routing with the use of the \_\_\_\_\_\_\_\_\_\_command.
EIGRP allows unequal-cost routing with the use of the ***variance #*** command.
93
If you have an active route with a metric of 10 and have feasible successors of 15, 25, and 55, you can adjust the variance number to make those routes active.
What commands would you need to issue to make each of these routes active?
1. If you use ***variance 2***, then the active metric of 10 gets multiplied by 2, which equals 20. Any feasible successor less than 20 gets added as an active route. The route with a metric of 15 is added, so you have two active routes.
2. If you use ***variance 3***, the routes with metrics of 10, 15, and 25 become active (3 × 10 = 30). Note that for this example, using a variance of 4 or 5 does not add the route with a metric of 55. You need to use a variance of 6 to add the route with a metric of 55 (6 × 10 = 60).
94
T/F: EIGRP for IPv6 is configured and managed separately from EIGRP for IPv4.
True.
95
T/F: EIGRP for IPv6 uses network statements at the interface level.
False. No network statements are used.
96
T/F: EIGRP for IPv6 uses all the same characteristics (network discovery, DUAL, modules) and functions as EIGRP for IPv4.
True.
EIGRP for IPv6 retains all the same characteristics (network discovery, DUAL, modules) and functions as EIGRP for IPv4.
97
T/F: EIGRP for IPv6 uses different metrics than EIGRP for IPv4 networks.
False. The same metrics are used.
98
In EIGRP for IPv6, the administrative distances are ___ for EIGRP internal routes, ___ for EIGRP external routes, and ___ for EIGRP summary routes.
In EIGRP for IPv6, the administrative distances are 90 for EIGRP internal routes, 170 for EIGRP external routes, and 5 for EIGRP summary routes.
99
EIGRP for IPv6 uses IPv6 multicast _______ for EIGRP updates.
EIGRP for IPv6 uses IPv6 multicast FF02::A for EIGRP updates.
100
T/F: IS-IS is a hybrid routing protocol that combines features from DV and Link State protocols.
False. IS-IS is a link-state routing protocol that floods link-state information throughout the network to build a picture of network topology.
101
T/F: As with OSPF, IS-IS uses the Dijkstra algorithm to calculate the shortest path tree (SPF)
True.
As with OSPF, IS-IS uses the Dijkstra algorithm to calculate the shortest path tree (SPF).
102
T/F: IS-IS uses link-state packets (LSPs) instead of OSPF link-state advertisements (LSAs).
True.
IS-IS uses link-state packets (LSPs) instead of OSPF link-state advertisements (LSAs).
Also, neither OSPF nor IS-IS are proprietary protocols.
103
How many levels of hierarchy are there in IS-IS?
IS-IS creates two levels of hierarchy, with Level 1 for intra-area routing and Level 2 for interarea routing.
IS-IS distinguishes between Level 1 and Level 2 intermediate systems (ISs). Level 1 ISs communicate with other Level 1 ISs in the same area. Level 2 ISs route between Level 1 areas and form an interarea routing backbone.
Hierarchical routing simplifies backbone design because Level 1 ISs only need to know how to get to the nearest Level 2 IS.
104
What does IS-IS stand for?
What is an ES?
Intermediate System-to-Intermediate System (IS-IS)
In IS-IS, a router is usually the IS, and personal computers, workstations, and servers are **end systems (ESs)**. ES-to-IS links are Level 0.
105
IS-IS, as originally defined, uses a composite metric with a maximum path value of \_\_\_\_\_\_.
Any single link can have a maximum value of \_\_\_\_.
IS-IS calculates path values by _______ link values.
IS-IS, as originally defined, uses a composite metric with a maximum path value of **1024**.
The required default metric is arbitrary and is typically assigned by a network administrator. By convention, it is intended to measure the capacity of the circuit for handling traffic, such as its throughput in bits per second. Higher values indicate lower capacity.
Any single link can have a maximum value of **64**.
IS-IS calculates path values by **summing** link values.
The standard sets the maximum metric values to provide the granularity to support various link types, while ensuring that the shortest path algorithm used for route computation is reasonably efficient.
106
In Cisco routers, all active IS-IS interfaces have a default metric of **\_\_\_\_\_**. If an interface is passive, the default value is \_\_\_\_\_.
In Cisco routers, all active IS-IS interfaces have a default metric of **10**. If an interface is passive, the default value is **0**.
107
What is a "wide-metric" in Cisco with IS-IS.
This is a 24-bit metric field, the “wide metric.”
Using the new metric style, link metrics now have a maximum value of 16,777,215 (224 – 1) with a total path metric of 4,261,412,864 (254 × 224 = 232).
108
T/F: IS-IS defines three optional metrics (costs): delay, expense, and error. Cisco routers support the three optional metrics.
True and False.
IS-IS also defines three optional metrics (costs): delay, expense, and error. **Cisco routers do not support the three optional metrics.**
109
What is a NET in IS-IS?
Network Entity Title.
IS-IS defines areas differently from OSPF; area boundaries are links and not routers. IS-IS has no BDRs. Because IS-IS is an OSI protocol, **it uses a NET to identify each router.**
**The NET is the OSI address used for each router to communicate with OSI PDUs.** (the communication between routers uses OSI PDUs)
110
A NET address ranges from _____ to _____ bytes in length and is expressed in a ______ format.
A NET address ranges from **8 to 20** bytes in length and is **hexadecimal**.
111
An IS-IS NET consists of an AFI, area ID, system ID, and a SEL.
What is an AFI and a SEL?
An IS-IS NET consists of an **authority and format identifier** (AFI), area ID, system ID, and **selector** (SEL), as shown in Figure 3-10.
The system ID must be unique within the network.
See attached diagram for an example of a NET.
112
An example of an IS-IS NET is 49.0001.1290.6600.1001.00 - what is the:
AFI:
Area ID:
System ID:
SEL:
AFI: 49
Area ID: 0001
System ID: 1290.6600.1001
SEL: 00
113
T/F: Level 2 routers use the area ID to define an area.
True.
Level 2 routers use the area ID.
114
What are the commands to configure IS-IS on a Cisco router?
router isis
net 49.0001.00aa.0101.0001.00
* AFI: 49
* Area ID: 0001
* System ID: 1290.6600.1001
* SEL: 00
115
T/F: As with OSPF, IS-IS selects DRs on multiaccess networks. It also chooses a backup DR, as OSPF does.
False.
As with OSPF, IS-IS selects DRs on multiaccess networks. **It does not choose a backup DR**, as OSPF does.
116
By default in ISIS, the priority value is \_\_\_. You can change the priority value to a value from ___ to \_\_\_. If you set the priority to \_\_\_, the router is not eligible to become a DR for that network.
By default, the priority value is **64**. You can change the priority value to a value from **0 to 127**. If you set the priority to **0,** the router is not eligible to become a DR for that network.
117
T/F: IS-IS uses the highest system ID to select the DR if there is a tie with the priorities.
True.
118
T/F: In IS-IS, on point-to-point networks, the priority is 0 because no DR is elected.
True.
119
T/F: In IS-IS, all routers in a multiaccess network establish adjacencies with all others in the subnetwork, and IS-IS neighbors become adjacent upon the discovery of one another.
True.
In IS-IS, all routers in a multiaccess network establish adjacencies with all others in the subnetwork, and IS-IS neighbors become adjacent upon the discovery of one another.
Both of these characteristics are different from OSPF behavior.
120
What are the two interface types available in IS-IS?
IS-IS only has two network types (or interface types): **point-to-point and broadcast.**
Unlike OSPF, IS-IS does not have nonbroadcast and point-to-multipoint interface types.
121
1. A ___ ISIS router is similar to an OSPF backbone router.
2. A ISIS router that has ___________ routes is similar to an OSPF area border router (ABR).
3. Level ___ ISIS routers are like OSPF internal routers in a Cisco totally stubby area.
1. A **L2** router is similar to an OSPF backbone router.
2. A router that has **both Level 1 and 2** routes is similar to an OSPF area border router (ABR).
3. **Level 1** routers are like OSPF internal routers in a Cisco totally stubby area.
122
With IS-IS, you can create three types of topologies. What are they?
With IS-IS, you can create three types of topologies:
1. Flat
2. Hierarchical
3. Hybrid
123
What type of IS-IS topology is depicted in the attached diagram?
The IS-IS flat design consists of a single area. As shown in Figure 3-12, all routers are on the same level. There is no summarization with this design. This design is recommended for a small network.
124
Which type of IS-IS topology is shown in the attached diagram?
An IS-IS hierarchical topology is recommended for large networks. A backbone area can be created, much as with OSPF, and can have other areas connected via L1/L2 routers, as shown in Figure 3-13. This design allows for network summarization.
125
Which IS-IS topology is shown in the attached diagram?
A hybrid IS-IS design is recommended for networks that might not be large enough for a backbone area. As shown in Figure 3-14, the IS-IS areas are connected using L1/L2 routers. This design allows for summarization between areas.
126
T/F: In and IS-IS network, all L2 and L1/L2 routers must be configured for authentication and must use the same password.
True.
Only L2 and L1/L2 routers use domain authentication. All L2 and L1/L2 routers must be configured for authentication and must use the same password.
127
All of the following characteristics of IS-IS are true, except two. Which are incorrect?
1. It is a hybrid protocol.
2. It uses OSI CNLP to communicate with routers.
3. It is a classless protocol (and supports VLSM and CIDR).
4. The default metric is set to 10 for all active interfaces.
5. IS-IS has two interface types: point-to-point and broadcast.
6. It uses a single path metric, with a single link maximum of 64 and a path maximum of 1024.
7. It sends partial route updates every 90 seconds.
8. IS-IS authentication uses plaintext passwords.
9. The administrative distance is 115.
10. It is used in large networks and is sometimes attractive as compared to OSPF and EIGRP.
11. IS-IS provides support for IPv4 and IPv6 as separate topologies.
1. It is a **link-state** protocol.
2. It uses OSI CNLP to communicate with routers.
3. It is a classless protocol (and supports VLSM and CIDR).
4. The default metric is set to 10 for all active interfaces.
5. IS-IS has two interface types: point-to-point and broadcast.
6. It uses a single path metric, with a single link maximum of 64 and a path maximum of 1024.
7. It sends partial route updates **only when there are changes.**
8. IS-IS authentication uses plaintext passwords.
9. The administrative distance is 115.
10. It is used in large networks and is sometimes attractive as compared to OSPF and EIGRP.
11. IS-IS provides support for IPv4 and IPv6 as separate topologies.
128
True or false: Link-state routing protocols send periodic routing updates.
False. Distance-vector routing protocols send periodic routing updates.
129
True or false: The path with the lowest cost is preferred.
True. The lowest cost is preferred.
130
True or false: A link with a reliability of 200/255 is preferred over a link with a reliability of 10/255.
True. The higher value for reliability is preferred.
131
True or false: A link with a load of 200/255 is preferred over a link with a load of 10/255.
False. The link with the lower load is preferred. The EIGRP route. EIGRP routes have an administrative distance of 90, and OSPF routes have an administrative distance of 100. The lower administrative distance is preferred.
132
On a router, both EIGRP and OSPF have internal routes to 198.168.10.0/24. Which route is injected into the routing table?
The EIGRP route. EIGRP routes have an administrative distance of 90, and OSPF routes have an administrative distance of 100. The lower administrative distance is preferred.
133
On a router, both RIPv2 and IS-IS have a route to 198.168.10.0/24. Which route is injected into the routing table?
The IS-IS route. IS-IS routes have an administrative distance of 115, and RIP routes have an administrative distance of 120. The lower administrative distance is preferred.
134
On a router, EIGRP has a route to the destination with a prefix of /28, and OSPF has a route to the destination with a prefix of /30. Which is used to reach the destination?
The OSPF route is used to reach the destination because it is a more specific route.
135
Which of the following is the best measurement of an interface’s reliability and load?
1. Reliability 255/255, load 1/255
2. Reliability 255/255, load 255/255
3. Reliability 1/255, load 1/255
4. Reliability 1/255, load 255/255
A. The best reliability is 255/255 (100%), and the best load is 1/255 (approximately 0%).
136
9. Which routing protocols permit an explicit hierarchical topology? (Choose two.)
1. BGP
2. EIGRP
3. IS-IS
4. RIP
5. OSPF
C and E. IS-IS and OSPF permit an explicit hierarchical topology.
137
What routing protocol parameter is concerned with how long a packet takes to travel from one end to another in an internetwork?
Delay is based on the amount of time it takes a packet to travel from one end to another in an internetwork.
138
Match each loop-prevention technique with its description.
1. Split horizon
2. Poison reverse
3. Triggered updates
4. Counting to infinity
1. Sends an infinite metric from which the route was learned
2. Drops a packet when the hop count limit is reached
3. Suppresses a route announcement from which the route was learned
4. Sends a route update when a route changes
i = C
ii = A
iii = D
iv = B
139
Which standards-based protocol would you select in a large IPv6 network?
RIPng
OSPFv3
EIGRP for IPv6
RIPv2
B. OSPFv3 is the only standards-based routing protocol in the list that supports large networks. RIPng has limited scalability.
140
Which of the following routing protocols are fast in converging when a change in the network occurs? (Choose three.)
1. RIPv1
2. RIPv2
3. EIGRP
4. OSPF
5. IS-IS
6. BGP
C, D, and E. Link-state routing protocols plus EIGRP’s hybrid characteristics converge faster.
141
If you were designing a large corporate network that cannot be designed in a hierarchy, which routing protocol would you recommend?
1. RIPv1
2. RIPv2
3. EIGRP
4. OSPF
5. IS-IS
6. BGP
C. EIGRP supports large networks and does not require a hierarchical network.
142
You are connecting your network to an ISP. Which routing protocol should you use to exchange routes?
1. RIPv1
2. RIPv2
3. EIGRP
4. OSPF
5. IS-IS
6. BGP
7. All of the above
F. BGP is used to connect to ISPs.
143
Which routing protocol would be supported on an IPv6 network with multiple vendor routers?
1. RIPv2
2. EIGRP for IPv6
3. BGPv6
4. OSPFv3
5. RIPv3
D. OSPFv3 is the only correct answer. RIPv2 is for IPv4 networks. EIGRP is not a standards-based protocol. BGPv6 and RIPv3 do not exist.
144
Which statements are true for IGPs and EGPs? (Choose two.)
1. IGPs can be substituted with static routing.
2. IGPs are better at finding the fastest paths across the network.
3. IGPs must converge quickly, but EGPs do not have to.
4. IGPs are for inter-autonomous system connections, and EGPs are used for intra-autonomous system connections.
B and C. IGPs converge faster than EGPs.
145
How is convergence related to routing information?
1. The speed of convergence affects the frequency of routing updates.
2. The faster the convergence, the less consistent routing information is produced.
3. The faster the convergence, the more consistent routing information is produced.
4. There is no relationship between convergence and routing information consistency.
C. Faster routing convergence means more accurate information.
146
Which EIGRP features make it appropriate for a company’s network? (Choose two.)
1. Slow convergence
2. VLSM support
3. DUAL
4. Automatic summarization
5. Multivendor support
B and C. EIGRP uses DUAL for fast convergence and supports VLSMs.
147
Match each protocol with its characteristic.
1. EIGRP for IPv6
2. RIPv2
3. RIPng
4. EIGRP
1. Uses multicast FF02::9
2. Uses multicast 224.0.0.9
3. Uses multicast 224.0.0.10
4. Uses multicast FF02::A
i = D
ii = B
iii = A
iv = C
148
Match each EIGRP component with its description.
1. RTP
2. DUAL
3. Protocol-dependent modules
4. Neighbor discovery
1. Provides an interface between DUAL and IPX, RIP, IGRP, and AppleTalk
2. Used to deliver EIGRP messages reliably
3. Builds an adjacency table
4. Guarantees a loop-free network
i = B
ii = D
iii = A
iv = C
149
Match each EIGRP parameter with its description.
1. Feasible distance
2. Successor
3. Feasible successor
4. Active state
1. The best path selected by DUAL
2. Successor down and no feasible successor available
3. The lowest calculated metric of a path to reach the destination
4. The second-best path
i = C
ii = A
iii = D
iv = B
150
On an IPv6 network, you have RIPng and EIGRP running. Both protocols have a route to destination 10.1.1.0/24. Which route gets injected into the routing table?
1. The RIPng route
2. The EIGRP route
3. Both routes
4. Neither route because of a route conflict
B. The EIGRP route has a lower administrative distance.
151
24. Which IGP protocol is a common alternative to EIGRP and OSPF as a routing protocol for large service provider networks?
1. OSPFv3
2. RIPv2
3. BGP4
4. IS-IS
D. IS-IS.
152
What is the default IS-IS metric for a T1 interface?
1. 5
2. 10
3. 64
4. 200
B. The default IS-IS cost metric for any interface type is 10.
153
In IS-IS networks, the backup designated router (BDR) forms adjacencies to what router or routers?
1. It forms an adjacency only with the DR.
2. It forms adjacencies with all routers.
3. The BDR only becomes adjacent when the DR is down.
4. There is no BDR in IS-IS
D. IS-IS does not define BDRs.
154
Which routing protocol converges most quickly?
1. BGP
2. OSPF
3. EIGRP
4. RIPv2
5. IS-IS
C. EIGRP.
155
Which routing protocol allows for unequal-cost multipath routing?
1. IS-IS
2. OSPF
3. EIGRP
4. RIPv2
C. EIGRP.
156
Which two link-state routing protocols support IPv6?
1. BGP4
2. EIGRP
3. OSPF
4. RIPng
5. IS-IS
C and E.
157
Which of the following are characteristics of EIGRP? (Choose four.)
1. ASN values must match to form neighbors.
2. It can use multiple unequal paths.
3. Summary routes have an AD of 150.
4. External routes have an AD of 170.
5. It exchanges the full routing table every 60 seconds.
6. It uses multicast address 224.0.0.10 for updates.
7. It does not support MD5 authentication
A, B, D, and F.
158
What does a hierarchical EIGRP design help with? (Choose two.)
1. Redistribution
2. Route summarization
3. Faster convergence
4. Load balancing
B and C.
159
Which are design considerations with EIGRP? (Choose two.)
1. The neighbor command is used to enable unicast communication.
2. The neighbor command can be used to establish adjacency with non-Cisco routers.
3. The ASN and K values must match to establish neighbors.
4. Virtual links can be used to establish neighbors over an area.
A and C.
160
Which are the two fastest converging routing protocols? (Choose two.)
1. IS-IS
2. OSPF
3. EIGRP
4. RIPv2
5. BGP4
B and C.
161
Which routing protocol uses multicast FF02::A and Next Header protocol 88?
1. IS-IS for IPv6
2. OSPFv3
3. EIGRP for IPv6
4. RIPng
C. EIGRP for IPv6.
162
What is the system ID of the NET49.0001.1900.6500.0001.00?
1. 49.0001
2. 0001.1900.6500
3. 1900.6500.0001
4. 0001.00
C. 1900.6500.0001 is the system ID, 49 is the AFI, and 0001 is the area ID.
163
EIGRP has a route with a metric of 20. There are two feasible successors with metrics of 35 and 45. If the variance 2 command is invoked, how many active routes are there for this route?
1. 1
2. 2
3. 3
4. 0
B. 2. The variance command configures EIGRP to accept unequal-cost routes with a metric of less than 2 × 20 = 40. The route with a metric of 35 is added.
164
Which routing protocol has the highest administrative distance?
1. RIP
2. EIGRP
3. OSPF
4. IS-IS
5. BGP
A. Administrative distances are BGP = 20, EIGRP = 90, OSPF = 110, IS-IS = 115, and RIP = 120.
165
Which routing protocol has the lowest administrative distance?
1. RIP
2. EIGRP
3. OSPF
4. IS-IS
5. iBGP
B. Administrative distances are EIGRP = 90, OSPF = 110, IS-IS = 115, RIP = 120, and iBGP = 200.
166
See attached diagram.
By default, if EIGRP is enabled on all routers, what path is taken?
1. Path 1
2. Path 2
3. Unequal-cost load sharing Path 1 and Path 2
4. Equal-cost load balancing with Path 1 and Path 2
B. Path 2 has greater bandwidth.
167
EIGRP is configured on the routers. If it is configured with the **variance 2** command, what path is taken?
1. Path 1
2. Path 2
3. Unequal-cost load sharing Path 1 and Path 2
4. Equal-cost load balancing with Path 1 and Path 2
C. Load sharing is enabled with the variance command.
168
By default, if EIGRP for IPv6 is enabled on all routers and this is an IPv6 network, what path is taken?
1. Path 1
2. Path 2
3. Unequal-cost load balancing with Path 1 and Path 2
4. Equal-cost load balancing with Path 1 and Path 2
B. By default, Path 2 has higher bandwidth and thus has the better metric.
169
By default, if IS-IS is enabled on all routers, and this is an IPv6 network, what path is taken?
1. Path 1
2. Path 2
3. Unequal-cost load balancing with Path 1 and Path 2
4. Equal-cost load balancing with Path 1 and Path 2
A. IS-IS chooses Path 1 with a metric of 10 over Path 2 with a metric of 30.
170
Which describes an EIGRP successor?
1. The path with the lowest metric to a destination
2. The route that satisfies the feasibility condition where the reported distance is less than the feasible distance
3. The path with the highest path metric to a destination
4. The path with the lowest path metric to a destination
D. The EIGRP successor is the path with the lowest metric.
171
Which route is used in the event that the successor route goes down?
1. The backup successor route
2. The feasible distance route
3. The feasible successor route
4. The reported distance route
C. The feasible successor is the backup route.
172
Which metric can be modified in EIGRP that does not affect the OSPF metric?
1. Bandwidth
2. Delay
3. Cost
4. Administrative distance
B. The EIGRP delay does not affect other routing protocols.
173
An EIGRP route is stable. What is its EIGRP state?
1. Active
2. Passive
3. Stuck in active
4. Disabled
B. The passive route is stable.
174
Which statement is true regarding IS-IS?
1. IS-IS supports only OSI and IPv4 routing.
2. IS-IS supports only IPv4 and IPv6 routing.
3. IS-IS supports only OSI and IPv6 routing.
4. IS-IS supports OSI, IPv4, and IPv6 routing.
D. IS-IS supports routing of OSI, IPv4, and IPv6 protocols.
