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CompTIA Network+ > Routing > Flashcards

Routing Flashcards

(89 cards)

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1
Q

router

A

any hardware or software that forwards packets based on their destination IP address

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2
Q

layers in each model where routers belong

A

OSI - network layer

TCP/IP - Internet layer

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3
Q

interfaces

A

at least 2 - 1 internal, 1 external

can have more

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4
Q

2 criteria in each column of the routing table

A

which packets are for the route

which port to send them out

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5
Q

destination LAN IP

A

defined network ID

every network ID directly connected to one of the router’s ports is always listed here

subnet mask is needed to define the network

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6
Q

gateway

A

IP address for next hop router

where the packet should go

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7
Q

gateway when directly connected to network

A

gateway not needed

value set to 0.0.0.0 or IP address or directly connected port

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8
Q

gateway when not directly connected to network

A

gateway column of the routing table tells the router the IP address of a router to send packet to

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9
Q

interface

A

tells router which of its ports to use

LAN / WAN

Port IP

fa0/0 & fa0/0 - Cisco

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10
Q

0 in routing table

A

means “anything”

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11
Q

default route (example)

A

[0.0.0.0] [0.0.0.0] [70.30.4.1] [WAN]

any destination address

with any subnet mask

forward to 70.30.4.1

using WAN port

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12
Q

default route (importance)

A

tells router what to do with every incoming packet unless another line in the routing table gives another route

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13
Q

2 places where routers do not have default routes

A

private internetworks - every router knows every network

tier 1 Internet backbone

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14
Q

other devices with routing tables

A

all TCP/IP capable devices

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15
Q

command to display routing table

A

netstat -r (OS X & Windows)

route print (Windows)

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16
Q

metric

A

relative value that defines the cost of using a particular route

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17
Q

adding interfaces to a router

A

removable modules are available for more powerful routers

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18
Q

NAT

A

network address translation

enables routers to hide internal IP addresses while still allowing communication with the broader Internet

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19
Q

how NAT functions

A

router replaces the source IP address of a computer is its outside interface address on outgoing packets

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20
Q

basic NAT

A

translates the private / internal IP address to the global IP address on 1-1 basis

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21
Q

primary reason NAT was created & conception of what it does

A

address the problem of limited IPv4 addresses

security / anonymity

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22
Q

PAT

A

port address translation

uses port numbers to route traffic from specific machine in the network

most common form of NAT that handles 1-to-many connections

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23
Q

how PAT functions

A

internal machine initiates a session with an external machine

source & destination IP addresses & port numbers for TCP segment / UDP datagram are recorded in PAT’s translation table

private IP address is swapped for public IP address on each packet

port number used by the internal computer for the session is also translated into a unique port number that is also recorded by router

receiving system returns packet - reverses IP addresses & ports

router compares incoming destination IP address & port number and compares to translation table - puts correct IP back on packet

sends to correct computer

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24
Q

PAT limitation

A

only works for outgoing communication, not incoming communication

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25
SNAT
static NAT maps a single routable (not private) IP address to a single machine enables access to that machine from outside the network
26
port forwarding
designate a specific local address for various network services request a service using the public IP address of the router & the port number of the desired service
27
how port-forwarding routers work
examines the packet & compares to list of services mapped to local addresses sends packet to appropriate computer
28
hiding hosted services inside network
change default port number for that service
29
DNAT
many computers can share a pool of routable IP addresses that number fewer than the number of computers LAN traffic uses internal IP NAT distributes routable IP from the pool for external requests
30
metrics only work when
there are direct connections between network IDs
31
hop
each time a packet goes through a router
32
metric
relative value that routers use when they have more than one route to get to another network router always chooses route with lowest metric
33
most common criteria for determining a metric
hop count bandwidth latency cost MTU
34
how many hops with 3 intermediate routers
4
35
latency
collective term that describes the large number of issues that may occur between routers that slow down network connections
36
MTU
maximum transmission unit largest frame a particular technology can handle
37
Ethernet frame size
1,500 bytes
38
fragmentation
packet is too large for a technology to handle broken down to fit in network's protocol slows down movement of packets
39
way to limit fragmentation
set optimal MTU size before sending packets
40
administrative distance
metric used by routers that use multiple protocols & thus can have multiple paths to the same destination
41
SPB
shortest path bridge routing metric standard to provide true shortest-path forwarding within Ethernet mesh topology supports large layer 2 networks by providing fast convergence & multiple, equal cost paths
42
distance vector routing protocols (definition)
calculate the total cost to a network ID & compare to the totals cost of all other routes to that network ID router chooses lowest cost route
43
distance vector routing protocols
total cost = hops between router & network 1 hop = cost of 1 can manually set cost of slower routes to 10
44
distance vector routing protocols - transfer of routing tables
routers transfer their entire routing table to other routes in the WAN each protocol has a maximum number of hops that it will send its routing table to limit traffic
45
convergence
steady state process of updating routing tables has been completed
46
distance vector routing protocols - convergence
routing tables are shared & updated all but lowest total cost route are deleted from table updated tables are shared again all routers only have the lowest total cost routes saved
47
distance vector routing protocols - limitation
smaller networks - less than 10 routers convergence would take too long
48
distance vector routing protocols - specific protocols
RIPv1 RIPv2 BGP
49
RIPv1
routing information protocol max hop count = 15 every router sent updates every 30 seconds - bogged down networks no authentication used
50
RIPv2
routing information protocol current version of RIP incorporates VLSM & uses authentication otherwise works the same as RIPv1
51
VLSM
variable-length subnet masking networks connected via a router use different subnet masks
52
AS
autonomous system 1 or more networks that are governed by a single dynamic routing protocol use ASN rather than IP addresses 2 16-bit numbers separated by a dot (1.33457)
53
ASN
autonomous system number globally unique identifier assigned by IANA
54
EGP
exterior gateway protocol used by AS's to communicate with each other
55
IGP
interior gateway protocol used by the network(s) within an AS to communicate with each other
56
border gateway protocols
many used within AS's i.e. RIP BGP-4 is standard for communication between AS's of the Internet
57
exam classification of BGP
hybrid protocol more accurately a path vector protocol
58
configuration of BGP routers
manual don't go down often
59
edge routers
AS to AS routers pass / advertise information i.e. ASN & other non-IP items
60
route aggregation
backbone routers track location of routers that connect to subsets of locations way to simplify routing tables into manageable levels supported by BGP
61
iBGP & eBGP
internal BGP & exterior BGP BGP can be used to connect routers within an AS
62
link state dynamic routing protocol
only announce & forward individual route changes instead of entire routing table OSPF & IS-IS
63
OSPF
open shortest path first most commonly used IGP on Internet designed to work within a single AS much faster convergence
64
LSA
link state advertisements packets sent by OSPF-capable routers to find other OSPF routers "hello packets" used to update link state databases
65
flooding
transmission of a lot of LSA packets when a router first comes online
66
determining OSPF cost
speed of the link 100,000,000 / bandwidth in bps 10BaseT 100,000,000 / 10,000,000 = 10
67
areas
groupings of routers to limit excessive broadcast while scaling up a network
68
backbone
central area in a network of interconnected areas assigned area ID all traffic between areas goes through backbone
69
area ID
0 or 0.0.0.0
70
ABRs
area border routers special routers that interconnect areas
71
frequency of hello LSAs upon convergence
~ 30 minutes unless break is detected in link state
72
break in link state is detected
routers attempt to reconnect > unsuccessful routers send LSA announcing broken connection each router updates table to remove broken route
73
benefits of OSPF
provides authentication prevents loops protocol of choice for large enterprise networks
74
IP version support in OSPF
OSPFv2 supports IPv4 OSPFv3 supports IPv6
75
IS-IS
intermediate system to intermediate system very similar to OSPF IPv6 compatible from the start standard for ISPs - rare to see in practice
76
EIGRP
enhanced interior gateway routing protocol developed by Cisco "advanced distance vector protocol" aspects of distance vector & link state protocols
77
route redistribution
router takes a route it has learned from 1 protocol & announces that route over another protocol routers can't communicate with different protocols can use multiple protocols simultaneously to perform route redistribution
78
connecting to a router
serial connection - Cisco - rollover or Yost cable usb RJ-45
79
managed devices
advanced switches & routers that require configuration
80
method of configuring router once connected
terminal emulation programs i.e. PuTTY & HyperTerminal
81
basic settings for serial connections
9,600 baud 8 data bits 1 stop bit no parity
82
console
screen you type into in a terminal emulation program
83
NMS
network management software software that interfaces with network hardware to provide an overall view of the network
84
[blank] are configured to use protocols
individual NICs - not entire routers protocols must match
85
common source of routing problems
error in routing table
86
commands for investigating routes
tracert - Windows traceroute - Unix/Linux
87
traceroute no longer works
something wrong between your router and the next router upstream
88
mtr
my traceroute continuous Linux tool
89
pathping
Windows tool that computes performance over a set amount of time & displays summary

CompTIA Network+ (9 decks)

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