EIGRP– Enhanced IGRP
EIGRP– Enhanced IGRP – cisco property – multiple routed protocol support only run in Cisco routers. No multi-vendor support (no other routers its won’t work).
Same network but different path
Fast Convergence
EIGRP – Hybrid LS and DV Combination of distance and link state Distance –forms the neighbors information,
Link state – first time send updates information. After that when changes occurred in the routing table or topology then only update.
AS no for admin convenience.
Administrative distance 90.
Support VLSM, Classless.
Dual algorithm (defusing update algorithm to find the best path with loop free). For finding the shortest path.
IGRP is run in same ASN as EIGRP, both automatically redistribute the routes.
Metric calculation base on the: Bandwidth, Delay, Load Reliability & MTU
Metric = 256*(K1*bandwidth+ k2*bandwidth/256-Load+k3*delay)*k5/reliablility+k4
Metric calculation base on the bandwidth (K1-1), delay (K3-1), reliability (K4-K5 -0) and load (K2-0).
Lowest metric is called successor.
First best path: stored in the routing table. Primary information is called successor.
Feasibility summarization (Auto Summarization or manual summarization at any interface or specific interface or Manual summarization at any router. Default auto summarization enabled. To disable Auto Summary use command:
# No auto-summary
Summarization:
# interface s0/0
#ip summary-address Eigrp 7 192.168.1.0 255.255.252.0 (subnet mask,
AD administrative Distance).
#ip summary-address eigrp 7 0.0.0.0 0.0.0.0
Hello Packets send 5 secs Multicast 224.0.0.10
Recognize the neighbors
Hello packets (MSG) send via 224.0.0.10- Must match: Same ASN, Same K Value, Same Authentication, same Subnet then only its forms neighbor relations.
Link goes down eigrp processed by next best path
Recognize the down state of neighbors
Hold time: 15 secs LAN, 60 Frame relay, 180 WAN
Per interface basics.
EIGRP ASN timer and hold timer can change.(Note: only change the hold timer don’t change hello timer) timer must be 1:3 (1hello: 3 Hold).
Successor router fails:
Two options:
Option 1 : router need to check for the feasible successor. If no feasible successor.
Option 2: The successor router need to run DUAL algorithm again to find a new loop free router to the destionation & add it to the routing table.
Backup Router (Feasible Successor)
Second best path: stored in the topology table. Feasible successor.
If routers have multiple paths enabled router meets FC.Backup router called feasible successor. Successor fails, FS feasible successor takes over.
If condition (FC) fail. There no feasible successor.
Unequal load balancing (Variance command)
Setup unequal cost load balancing assign a variance of 2 under eigrp process which multiple of the best matric value. After that now uses all loop free path which is less than the multiple of best matric value.
#router eigrp 7
# Variance 2
support default - 4 rotuers, 6is max. new rouers Max 16
# Maximum-pat No
no - 1,2,3,4...
#show ip protocol
Authentication between two routers. Its use only MD5. (Preconfigured, shared password) each of the (routing update packets also) packets verify if matches then only allow.
key chain, MD5, Key number (multiple number),
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).Routing table updates whenever changes occurred that time it will update.
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).Routing table updates whenever changes occurred that time it will update.
Eigrp Tables
EIGRP Maintaining 3 tables:
Routing Table: Successor information store. Routing table contain the best route information. Best route : successor lowest metric
Neighbors table: Neighbor table built from Eigrp hellos and used for reliable delivery.
Topology Table: contain Eigrp routing information for best path (successor) /and loop free alternative path (feasible successor) in this table.
best route but less desirable but still valid
(FS Backup route)
FS = Reporting Distance (Advertise D) < Feasible D of Successor – For Loop Preventing
Status
Active: Bad - Router become invalid into action to get FS (Feasible successor).Looking for backup. Query sends to find the backup.
Passive: Good – Everything working normal.
EIGRP Packets
5 types of packets:
Hello packets: Hello packets send every 5 secs to discover neighbor router to keep alive (using multicasting address 224.0.0.10) to form neighbor relation.
Hold timer 15secs in T1 or point to point line. If less than t1 line hello packet send every 60secs and hold time 180 secs.
Note: EIGRP first starts its uses hello packets to build neighbor table. Neighbors are directly attached router that has to match AS (autonomous system) and K value.
Updates: send the routing table with updates. (if any changes in the topology table update).
Query: requesting specific route information.
Reply: respond to Query.
Ack: the update query and reply msg acknowledgement.
EIGRP Configuration
#router EIGRP 7(7 autonomous system no)
#network17.16.0.0 (network)
Or only specific range or only one ip
#network172.16.0.0 0.0.0.255(network id and wcm)
Default route:
# ip default route 0.0.0.0
#ip route 0.0.0.0 0.0.0.0 10.1.1.2 (Next hop)
#router eigrp 7
#network 0.0.0.0
Passive – Interface: Passive interface prevent either routing update or hello msg from send out an interface.
#passive-interface interface f0/0
Turnoff all the protocol all interface:
#passive- interface default
1. To disable Auto Summary use command:
# No auto-summary
Summarization:
# interface s0/0
#ip summary-address Eigrp 7 192.168.1.0 255.255.252.0 (subnet mask,
AD administrative Distance).
#ip summary-address eigrp 7 0.0.0.0 0.0.0.0
#router eigrp 7
# Variance 2
support default - 4 rotuers, 6is max. new rouers Max 16
# Maximum-pat No
no - 1,2,3,4...
#show ip protocol
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
# IP authentication mode eigrp ASN MD5
# ip authentication key chain eigrp ASN name
name - key chain value
command to see
#show key chain
#debug ip eigrp packets (can find the key string value miss matching).
Trouble Shooting Commands
Show ip router – routing table
Show ip route - connected route
Show ip route - connected route
Show ip Eigrp router – only route learnt from Eigrp
Show ip protocols – verifies autonomous system, timer value, identify networks, EIGRP neighbors (routing information successor)
Show ip eigrp topology: identify successor and feasible successor
Show ip eigrp neighbors: neighbors table.
Show ip eigrp traffic - amount & type of eigrp msg.
Show ip eigrp interface e0
Show ip eigrp traffic - statics regarding EIGRP MSG send/receive.
show ip eigerp accounting - display eigrp RID/ ASN
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