beef410's version from 2018-03-26 17:12


Question Answer
NeighborshipNew neighbor's exchange full routes, hello times do not need to match(bad practice tho)
UpdatesAfter initial exchange only sends an update with a change in the network. Update only contains changes
MetricUses bandwidth and delay
EIGRPFormerly cisco-proprietary, supports VLSM and CIDR
ConvergenceOccurs rapidly due to feasible successor's being pre-calculated to take the place of existing failed successor routes
Protocol SupportIP IPX Appletalk
Hello224.0.0.10 to establish neighbors uses RTP
RTPReliable Transport Protocol
AS / ASNAutonomous System Number - routers in different AS's cannot become neighbors
AdjacencySame subnet, k-values must match, same AS, hello/dead timers do not have to match, not a good idea though
SuccessorCurrent best route
Feasible SuccessorBackup route
sh ip eigrp routerouting table best routes
sh ip eigrp topShows best routes and all known loop-free routes
sh ip eigrp neighborShows neighbors - addr/uptime/seq num
Network statement(config-router)# network <IP> <wild> ; Without wild bits EIGRP will uses classful subnetting. Advertises stated network
Split HorizonRouter cannot advertise a route back out the same interface it was received. Problem for hub-spoke over cloud setups. Disabled on the int
(config-if)# no ip split-horizon eigrp <as>Disables split horizon
Load BalancePerform equal-cost load balancing by default, adjust variance for unequal cost load balancing
Hello Interval (config-if)# ip hello-interval eigrp <as> <sec> default 5s
Hold TimeDefault 3times hello interval, 15s. WILL NOT AUTOMATICALLY ADJUST LIKE OSPF
Hello Timedefault 5s on fast linksLAN / 60s on slow links WANFrame Relay+T1, can see with sh ip eigrp int detail
VarianceDefault 1, multiplier of FS metric, used to determine load balancing. Used smallest multiplier possible to achieve desired load balancing. sh ip proto eigrp to see
Topology TableWill show all routes and states. P passive A active, P means no calculation happening, A means EIGRP is calculating routes. Should be all P's.
Variance 2Large variances can prompt EIGRP to ignore very large metric paths
DUALDiffusing Update ALgorithm, if an existing route is lost it will query neighbors till a route is found or the missing network is determined non-existent.
StubsIndividual routers are made stubs. Won't be queried by DUAL.
RIDPriority Set by eigrp router-id command -> highest IP on any up/up loopback -> highest IP on an up/up physical int.
(config-router)# eigrp router-id Sets RID, like OSPF will flush adjacencies.
Forming AdjMutli-cast -> Unicast FullUpdate -> Ack FullUpdate -> Ack
Fallping AdjMost common caused by hello time > hold time
Feasible DistanceFirst number in the brackets of the top table. Full metric of route
Reported DistanceSecond number in the brackets of the top table. Distance from next hop to destination. Only shown in top table
FD > RDMeans loop free
Feasibility Condition for feasible successorRD of FS must be less than the FD of the successor, loop prevention. Variance will not change this
ADD 90 - D EX170 - Manual Summaries 5
(config-router)# redistribute connectedPulls connected routes into the EIGRP table using D EX 170 AD
Discontiguous networksOne major network number is separated by another. Auto-summary can see two major-network-number subnets as the same network
AutoSummarySeen by sh ip proto, default for EIGRP is off.
Passive Interface(config-router)# passive-interface fast 0/0 ; or <default> stops the sending of hellos
K valuesBandwidth, load, delay, reliability, MTU. 1,0,1,0,0 default uses bandwidth and delay. Mismatched K values will fail an adjacency. sh ip proto
(config-router)# metric weights 0 1 0 1 0 0Configure K values, extra leading 0 must be zero and is not a K value.
Goodbye MessageSent when EIGRP stops between two neighbors and the adj is lost while the link remains. IE removing a network statement or turning off EIGRP. Faster than waiting for timeouts
(config-if)#ip summary-address eigrp <as> <summedIP> <netmask>Summary address, determined by where summarized routes stop matching in binary. Summaries gracefully apply changes
(config-if)# bandwidth <kbits>Configures per-int bandwidth in kbits
(config-if)# delay <tens of microseconds>Configure int delay value in kbits

Show Commands

Question Answer
sh ip eigrp routerouting table best routes, like OSPF won't show C routes.
sh ip eigrp topShows best routes and all known loop-free routes
sh ip eigrp neighborShows neighbors - addr/uptime/seq num
sh ip eigrp trafficHellos/updates/queries/replies/acks
sh ip eigrp int detailTimer info

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