0EIGRP-Enhanced Interior Gateway Routing Protocol
*It is Open Standard protocol since March 2013.
*It works on network layer
*Denoted by - "D" and "D EX"
*It is a Hybrid Routing Protocol having the properties of Distance vector and Link State Routing Protocols.
*It uses Multicast address 224.0.0.10 to send its update.Eigrp only sends trigger updates and updates only contains the change. Eigrp uses protocol no 88.
*It uses DUAL-Diffusing Update Algorithm to find best path among all
available paths.Dual also helps in finding loop free path and backup path.
*Eigrp uses the concept of Autonomous System and will form neighbor
relations with the routers in same AS and should be directly connected.
AS-Group of routers managed by single administrative domain.1-65535
*Eigrp uses RTP-Reliable Transport Protocol to ensure delivery of most Eigrp packets.
*Eigrp is classless protocol but if left on default conditions it behave as classfull.So to change the behaviour to classless use "no auto-summary" command under Eigrp configuration.So EIGRP supports VLSM.
*Eigrp supports routing for IP,IPX and AT(Apple Talk).
*Eigrp applies AD(Administrative Distance) of 90 to routes originated within an AS.And AD value of 170 to routes coming from different AS or different domain.
*Eigrp by default Hop Count is 100 but we can extend upto 255.
*Eigrp Supports MD5 authentication to authenticate the neighbor.
*TIMERS
On fast links
Eigrp Hello=5 sec
Eigrp Hold=15 sec
On slow Links like Frame-Relay-
Eigrp Hello=60 seconds
Eigrp Hold=180 seconds
*EIGRP Packets
Hello -
Update -
Query -
Reply -
Ack -
*Eigrp maintains three tables-
a-Neighbor Table-Information about all neighbours are stored in this table.
b-Topology Table-Information about Successor and Feasible Successor is present in this table. This table also gives us the information about route states, FD, AD/RD etc.
c-Routing Table- Best route(Successor route) is installed in the Routing Table.
*Very fast conversion -
1. best path (routing table)
2. second best path (topology table)
*It calculates its Metric on Bandwidth(K1) and Delay of the line(K3)
By default. Other parameters can also be used in the calculation. Following are the parameters-
a- K1=Bandwidth =1
b- K2=Load =0
c- K3=Delay =1
d- K4=Reliability =0
e- K5=MTU-Maximum Transmission Unit =0
Eigrp Metric is called Composite Metric.
*Eigrp terms-
a-Successor-The best path to reach the destination and is installed in RT.
b-Feasible Successor-It is the backup path and will only be installed
in RT when the Successor route goes down.
c-Feasible Distance-FD-Its the total Metric to reach the destination.
d-Advertised Distance/Reported Distance-It is the Metric advertised or
reported by the neighbour router to local router to reach the destination
*EIGRP neighborship condition
ASn, k-value, and authentication must be the same
* the Eigrp Route States-
a-Passive-If routes are in a passive state; this indicates that Eigrp is
fully converged and all available paths are valid and in working condition.
b-Active- If routes are inactive state, this indicates eigrp is querying other routers for an alternate path. This is not a good
indication of Eigrp synchronization. A way goes into active
state only if there is no Feasible Successor present.If a
FS is present and Successor goes down router will never send
queries to other routers as FS will be installed in RT as
Successor. So, a route goes into active state if Successor goes down and
there is no Feasible Successor present for backup.
c-SIA-Stuck In Active-A route is placed in SIA state if reply for query
is not received within 3 minutes.Then router will clear
neighborship with that router which has failed to reply.
Neighborship will be created again after clearing.
*Eigrp Stub-This feature is used to limit the query packets.
When a Successor route goes down and no FS is present router
sends query packets to all its neighbor asking for alternate
path for that destination.If any router is configured as Stub
no query messages will be sent to that router.
*Eigrp Passive Interface- Passive interface is used to filter control
plane traffic.If any interface is configured as passive in Eigrp
that interface cannot send or receive updates. So passive-interface should be used carefully and only where we need not send Eigrp packets.
Note-If interface is configured as passive under any protocol configure-
tion, that interface will behave as passive only for that protocol.
*Show commands for EIGRP.
R1#show ip eigrp neighbors --to check eigrp neighbor table
R1#show ip eigrp topology --to check eigrp topology table
R1#show ip eigrp topology all --to check all route information in Topology
R1#show ip routes eigrp --to check eigrp routes in routing table
R1#show ip eigrp interfaces detail s0/0 --to check hello timer
DEBUG COMMANDS FOR EIGRP
R1#debug eigrp packets
This command will start debugging for all eigrp packages.To debug a
Particular packets select option for that specific packet.
e.g
to debug only hello, issue the following command
R1#debug eigrp packet hello
R1#debug ip packet detail --to check whether eigrp is multicasting or unicasting
