Please help me to understand this Q

[Amr Ali]

Hello Sirs,

Kindly i need help to understand this question

Best regards - amr

[InayathUlla Sharieff]

Whats the query?

[Jan Rolny]

Hi Amr,

answer is: because auto-summary is turned on. Network 172.16.5.x /28 is summarized to 172.16.0.0 network. You need to configure no auto-summary command to let router know about "remote/neighbor networks".

auto-summary tells your router that only classful subnetmasks (255.255.0.0 in this case) will be used.

Also please read this document where it is litle bit explained:

http://www.ciscopress.com/articles/article.asp?p=174107&seqNum=3

Regards,

Jan

[Sandeep Choudhary]

Hi Amr,

This Command: show ip route  on RouterB shows that Router B did not learn the network from Router A.

It only learn which is directly connected to Router B menasnetwork is summarized as also shoes by 00:00:03, Null0″ line

or

If you look carefully at the R2 ip route, you will discover that the R2 does not learn any network from R1; this is because the routing protocol used here (EIGRP) performs auto summary when advertising routes to peers across a network. So in this case the address 172.17.0.0/26 is a summarized address. If the router was configured with no auto summary command, R2 LAN addresses would have been advertised and reached.

Hope it helps.

Regards

[Amr Ali]

Thanks experts for your efforts