eigrp-notes

cagamosisthingyΔίκτυα και Επικοινωνίες

27 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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EIGRP Notes



Cisco Proprietary Protocol



Advanced distance vector



Automatic summarization at classful boundary (can be disabled/turned off)

o

supports VLSM/CIDR

o

manually summarized routes have AD of 5, point to NULL0

o

more specific routes within summarized rang
e must exist in routing table,
or summarized route disappears



multicast address 224.0.0.10

o

Unicast and multicast are used for updates



IP/IPX/Appletalk routed protocol support



no special configuration required for various layer 2 technologies



Unequal cost l
oad balancing



Successor
-

Best path to a destination



Feasible sucessor
-

second best path to a destination

o

Advertised Distance
-

cost from next hop to final destination

o

Feasible Distance
-

cost from local router to final destination

o

For Feasible successor
to be used, AD must be less than the FD through
successor



Hello Packets are sent every 5 seconds on links greater than T1

o

sent every 60 seconds for T1 and slower

o

hold time interval defaults to 3 times the hello interval

o

changing default hello interval does

NOT automatically update the hold
time

o

ip hello
-
interval eigrp {as} {seconds}
interface command

o

ip hold
-
time eigrp {as} {seconds}

interface command



Un
-
acknowledged multicast updates are unicast to the host that did not ack. This
avoids hold ups with furt
her updates to the rest of the network



EIGRP metric is based on load, bandwidth, delay, and reliability.

o

Cisco recommends leaving k values at default



Configuration of EIGRP

o

router eigrp {as}

o

network {address | wildcard mask} (wildcard is optional)

o

no aut
o
-
summary (turns off summarization at classful boundary)

o

redistribute static (redistributes any static routes into the protocol)

o

variance {#} (modifies which routes will be considered for unequal cost
load balancing)

o

max
-
paths {#} (number of paths to be us
ed for load balancing. default is 4,
max is 16)

o

ip summary
-
address eigrp {as} {address | mask} (interface configuration
command to summarize routes at a non classful boundary.)

o

eigrp stub
receive
-
only

( this creates a stub in eigrp. The “receive
-
only
opti
on” tells the stub router to not send ANY routes)



EIGRP Authentication

o

EIGRP supports cleartext and MD5 authentication. It looks like we’re
only concerned with MD5 for the exams (for obvious security reasons)

o

ip authentication mode eigrp {as} md5
(interfa
ce config mode)

o

ip authentication key
-
chain eigrp {as} {name of keychain}

o

key chain {name of keychain}
(global config mode)



key {key
-
id}
(this can be between 0
-
2147483647)



key
-
string {key}



As of IOS 12.3, EIGRP sends a graceful goodbye message when bringin
g the
process down. Goodbye messages are sent inside of Hello packets



Helpful Commands

o

show ip eigrp neighbors

o

show ip route

o

show ip route eigrp

o

show ip protocols


shows active routing protocol info (displays k values)

o

show ip eigrp interfaces

o

show ip ei
grp toplogy


successor/feasible successor

o

show ip eigrp traffic

o

debug eigrp packets



Key technologies

o

DUAL Finite State

o

RTP

o

Neighbor discovery/recovery

o

Protocol dependant modules (ip, ipx, appletalk)