ICND2 Flashcard: EIGRP

EIGRP = Enhanced Interior Gateway Routing Protocol

It is a Cisco proprietary, Advanced Distance Vector metric. Some folks may refer to it as a hybrid routing protocol, but it is truly not.  EIGRP uses Hello packets, much like a link state protocol

Advertised distance - EIGRP metric for blank to reach network
Feasible distance - the metric to reach neighbor + the advertised distance

Features of EIGRP
Rapid convergence using Diffuse Update Algorithm (DUAL) guarantees loop free paths and backup paths.  If the primary route in the table fails, the best backup route is added to the table immediately. If no route exists, EIGRP queries the neighbors.

Reduced bandwidth by not sending the entire database and instead using:
Partial updates: only include route changes, incremental updates and not the whole table
Bounded updates: only send updates to routers affected

Multiple Network Layer Support can do Appletalk, IP, IPv6, Novell (IPX)

Less Overhead by using multicast and unicast, not broadcast. The ip address 224.0.0.10 is listed in my notes

Classless Routing
The mask is advertised for each network as this provides smaller subnets and efficient use of IP addresses.  The protocol can also support discontiguous subnets and VLSM (variable length subnet masks)

Load Balance
The protocol allows load balancing on equal (by default) and unequal cost paths. Caveat, for unequal cost paths, variance must be specified.

EIGRP does equal metric load balancing by default up to four equal metric routes. This means the variance value is 1 (default).  The routing table can have 16 entries for the same destination.

Configuring EIGRP
usage: conf t
router eigrp 100 (automonous system 100, 1 to 65535 possible)
network 10.0.0.0
network 192.168.10.0 0.0.0.15 (the wildcard mask can advertise subnets now)
no auto-summary (what does this do?)
variance 2

Verifiy EIGRP
show ip route eigrp
show ip protocols
show ip eigrp interfaces
show ip eigrp int fa 0/0
show ip eigrp int 100
show ip eigrp topology
show ip eigrp topology all-links
show ip eigrp traffic (this command lists number of packets sent/ received; HELLO, updates, queries, replies, ack etc)

More about the Variance Command
This command allows unequal metric load balancing, metrics being
* bandwidth
* delay
* reliability - the most reliable based on keepalives
* load
* K value - calculation method and AS number must match

Troubleshoot EIGRP
show ip eigrp neighbors
show ip int brief (shows which interfaces are active)
show ip int fa 0/0 (see ip subnets)
show ip protocols (see routing for networks)
show ip eigrp int (check for the process id and the same K method)
debug eigrp packets

show ip route (displays all the routes and eigrp is labeled)
show ip eigrp topology (shows the router id with the highest IP address which should be the loopback 0)