Routing

Question 1

routing decisions

Answer 1

layer 3 to layer 2 mapping
routers use arp cache to map ip to mac
make forwarding decisions based on its internal routing tables

Question 2

routing table

Answer 2

table kept by router to determine which route entry is the best for the network
a route entry with the longest prefix is the most specific
ex: 10.1.1.0/24 is more specific than 10.0.0.0/8

Question 3

learning routing information

Answer 3

directly connected routes: physical connection w/ cables
static routes: manually configured by admin
dynamic routing protocol: learned by exchanging info between routers

Question 4

prevent routing loops

Answer 4

split horizon: prevents a learned route on one interface to be advertised back out the same interface
poison reverse: causes a learned route on one interface to be advertised back out the same interface at an extremely expensive cost

Question 5

igp

Answer 5

interior gateway protocols

operate within an intranet

Question 6

egp

Answer 6

exterior gateway protocols

operate between external networks

Question 7

distance vector

Answer 7

uses hop count as a metric
sends full copy of routing table
slow convergence time

Question 8

link state

Answer 8

uses cost (speed) or other factors as a metric
requires all routers know about the paths that other routers can reach
faster convergence
each router constructs its own relative shortest-path tree with itself at the root

Question 9

rip

Answer 9

routing information protocol
interior gateway protocol
distance vector/ hop count (15, 16)
oldest, easy, udp
vslm

Question 10

ospf

Answer 10

open shortest path first
interior gateway protocol
link state using cost (link speed)
vlsm

Question 11

eigrp

Answer 11

enhanced interior gateway routing protocol
hybrid distance and link state
cisco only network
vslm

Question 12

bgp

Answer 12

border gateway protocol
external gateway protocol
path vector using system hops instead of router hops
backbone of internet
slow convergence

Question 13

ad

Answer 13

administrative distance
index of how to choose what routing protocol to use
the lower the ad, the more believable
from most to least believable
direct connection> static config> eigrp>ospf>rip>external eigrp> unknown

Question 14

pat

Answer 14

port address translations
variation of address translation but uses port numbers instead of private ip addresses
common in small networks

Question 15

dnat

Answer 15

dynamic network address translation
ip addresses automatically assigned from a pool
many to many translations

Question 16

snat

Answer 16

static network address translation
ip addresses manually assigned
one to one translations

Question 17

multicast routing

Answer 17

src sends traffic only to devices that want it (multicast group)
use igmp and pim

Question 18

igmp

Answer 18

internet group management protocol v3
let routers know which interfaces have multicast receivers
use by clients to join a multicast group

Question 19

pim

Answer 19

protocol independent multicast

forms a multicast distribution tree by routing multicast traffic