EIGRP Over NBMA Configuration Basics

eigrp over nbma example

This configuration is an example of EIGRP Over NBMA configuration. EIGRP Over NBMA is a form of EIGRP configuration.

eigrp over nbma example

1) Configure EIGRP with AS 25.
Each router should make summarization to decrease the routing table.
Make the configuration for that EIGRP uses %30 more bandwith due to default config. ( On the serial interface of the HO router ).
Enable authentication on all EIGRP routers using the authentication keys below.

KEY-1=passphrase : cisco1
Accepted from : Midnight on Jan 1 2010 until mid. On Feb 1 2010
Sent from :

KEY-2=passphrase : cisco2
Accepted from : Jan 28 2010 until eternity
Sent from :


R1#show ip route is variably subnetted 3 subnets ,2 masks
D is a summary,Null 0   
C is directly connected is variably subnetted ..         
D is a summary, Null 0
C is directly connected
B via ..
C is directly connected

“Null 0” routes are created if only there is one subnet learnt by EIGRP and auto-summary is activated.
HO Router:                   (A)

HO(config)#router eigrp 25
HO(config-router)#no auto –summary

If auto-summary is not closed, all the routers ( HO, EAST and WEST announce that to cloud and no neighborship can be established.

East Router:                  (B)

East(config)#router eigrp 25
East(config)#no auto

West Router:

West(config)#router eigrp 25
West(config)#no auto

After A – B and C configurations steps lets do a show ip route on EAST router…

East#show ip route

As you see, , and is not in the routing table. But you can see these networks in the HO router’s routing table. After the configuration step “D” you can see , and in the East router’s routing table too.
HO Router:                   (D)

HO(config)#interface s 0/0.1
HO(config-if)#no ip split–horizon eigrp 25       // split horizon was closed for eigrp 25 //

FOR HO:         // //

HO & East & West Routers:                                     (E)     

HO(config)#interface s0/0.1
HO(config-if)#ip summary-address eigrp 25     // config for summarization which is wanted at question 2 //
East(config)# int s 0/0.1          (F)
East(config-if)#ip summary-address eigrp 25

West(config)# int s 0/0.1       (G)
Wast(config-if)#ip summary-address eigrp 25


* Defaultly EIGRP uses %50 of the interface bandwidth and it is divided to neighbour count.

HO(config)#interface s0/0.1
HO(config-if)#ip bandwidth-percent eigrp 25 80

HO Router:

HO(config)#key chain EIGRP_KEYS
HO(config-keychain)#key 1
HO(config-keychain-key)#key-string cisco1
HO(config-keychain-key)#accept –lifetime 00:00:00 1 Jan 2010 00:00:00 1 Feb 2010
HO(config-keychain-key)#send –lifetime  …
HO(config-keychain)#key 2
HO(config-keychain-key)#key-string cisco2
HO(config-keychain-key)#accept –lifetime 00:00:00 28 Jan 2010 infinite
HO(config-keychain-key)#send –lifetime  …
HO(config)#interface s0/0.1
HO(config-if)#ip authentication made eigrp 25 md5
HO(config-if)# ip authentication eigrp 25 EIGRP_KEYS

This is how the question 4 is answered.”Key String” refers to the password given, if the key-strings don’t match no neighborship can be established. ” Accept-Lifetime and “Send-Lifetime” refer to how long the created passwords will be sent and received “. Pay attention that EIGRP supports only MD5 authentication.

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