Flashcards in Vol 1 Part 6: OSPF Deck (65)
What are the 4 routing protocols used for learning routes?
If more than one possible route exists to reach one subnet, what does a router do to pick the appropriate route?
It picks the best route based on a metric.
What are the two major IP routing protocols?
Interior gateway protocol (IGP) and exterior gateway protocol (EGP)
What is IGP designed to be used with?
Inside a single autonomous system, (AS) ie a company, a website, etc.
What is EGP designed to be used with?
Between different autonomous systems ie. apple and microsoft, spectrum and comcast etc.
What are the three main branches of IGPs?
1. Distance Vector (AKA Bellman-Ford)
2. Advanced Distance Vector (AKA Balanced Hybrid)
What are the 3 categories of the distance vector IGP?
3. IGRP (Cisco proprietary)
What kind of IGP is OSPF?
What Cisco proprietary IGP (no longer cisco proprietary) is faster than OSPF, and what kind of IGP is it considered?
EIGRP. It is a Hybrid/Advanced Distance Vector
What metric does RIPv2 use when picking the best route?
Hop count (number of routers/hops between a router and the destination subnet)
What metric does OSPF use when picking the best route?
Cost (sum of all the interface cost settings for all links in a route, with the cost defaulting based on interface bandwidth)
What metric does EIGRP use when picking the best route?
Composite of bandwidth and delay (calculated based on the route's slowest link and the cumulative delay associated with each interface in the route)
Which IGPs are classless (sends mask in updates/supports VLSM)?
RIPv2, EIGRP, and OSPF. RIPv1 is NOT classless.
Which IGPs support manual summarization and which ones do not?
RIPv2, EIGRP, and OSPF support manual summarization. RIPv1 does not.
When two companies use different routing protocols such as OSPF and EIGRP and they MUST communicate, what must happen so that each router has the appropriate routes?
What does OSPF use to exchange data about networks between routers?
Link State Advertisements (LSAs)
What command is used to show the LSA database?
Show ip ospf database
How often do routers re-flood each LSA?
Every 30 minutes
What are the three phases that OSPC uses to accomplish LSA exchange and calculate routes?
1. Become neighbors
2. Exchange LSA databases
3. Adding the best routes by running the SPF algorithm, based on the local copy of the LSA Database (LSDB)
Remember! A router can calculate the best routes from that routers perspective and add it to its own IPv4 routing table!
What must be in place in order to become neighbors with another router?
1. Same data link and use OSPF
2. Same VLAN, serial link, or ethernet WAN link
3. Use OSPF hello messages between routers
4. OSPF parameter compatibility
What command is used to see a router's neighbord?
show ip ospf neighbor
What does a router have that is unique to in and identifies it on the network?
A router ID (RID). It is simply the router's IPv4 address.
How does a router obtain a neighbor's RID?
With a Hello message
The Hello message follows an IP packet header with IP protocol *BLANK*?
Hello packets are sent to a multicast IP of *BLANK* for all OSPF speaking routers
What two timers MUST be the SAME for all routers on a link in order to establish a neighbor relationship?
The Hello and Dead timers
When establishing neighbors, both routers start down and then enter what state? And what happens after each router is in this state?
2. The routers send RIDs between each other
Once both RIDs are seen, the routers enter what state (hint: its the state after INIT)?
If a router does not have an LSA, it will ask for it specifically to get the details of the network information it contains. The message that sends the LSAs is called what?
Link Status Updates (LSUs)