BGP PEER

[alihassan1618]

Another Question to incease the knowledge! just want to learn how a device reflects to logs, i'm mean from below mention exhibit can i say that DSW1 is having ip 51.51.51.1 and received invalid packet packet from 5.0.0.5? Please read below question and correct me if i'm wrong. Thanks is advance.

All neighbor routers are in the BGP peer group named PEER-1 All passwords are configured as Cisco. These messages are logged to the console of router DSW1 which is peering with router Core. Which two configurations allow a peering session to form between DSW1 and the Core? (Choose two)

A. Core(config-router)#neighbor 5.0.0.5 peer-group PEER-1 Core(config-router)#neighbor PEER-1 password cisco
B. DSW1(config-router)#neighbor 5.0.0.5 peer-group PEER-1 DSW1(config-router)#neighbor PEER-1 password cisco
C. DSW1(config-router)#neighbor 51.51.51.1 peer-group PEER-1 DSW1(config-router)#neighbor PEER-2 password cisco
D. Core(config-router)#neighbor 51.51.51.1 peer-group PEER-1 Core(config-router)#neighbor PEER-1 password cisco
E. Core(config-router)#neighbor 5.0.0.5 peer-group PEER-2 Core(config-router)#neighbor PEER-1 password cisco

[Giuseppe Larosa · Accepted solution]

Hello AliHassan1618,

your understanding is correct the error message on DSW1 is related to receveing a BGP message with uncorrect MD5 digest from 5.0.0.5 to 51.51.51.51 on TCP well known port 179.

So the local address on DSW1 is 51.51.51.51 and remote is 5.0.0.5.

Please note that the question states :

>> All neighbor routers are in the BGP peer group named PEER-1 All passwords are configured as Cisco

Passwords are case sentitive. This should be the root cause for the seen mismatch.

Possible corrective actions are:

>> B. DSW1(config-router)#neighbor 5.0.0.5 peer-group PEER-1 DSW1(config-router)#neighbor PEER-1 password cisco

A and C and E are wrong because they are referring the local address as a remote.

>> D. Core(config-router)#neighbor 51.51.51.1 peer-group PEER-1 Core(config-router)#neighbor PEER-1 password cisco

Both B and D are needed to form a session between Core and DWS1 devices.

To be noted configuration on Core device will affect all devices that are members of PEER-1 peer-group.

Hope to help

Giuseppe