This indicates that genereally two routers wont advertise or send updates unless they form neighbour ship,But here as they not forming any neighbhour ship how can they caommunicate they cant rit? i saw a post (Wael Osama told that the passive interface command is to be able to advertise the interface subnet without forming adjacency on that interface how ?) what is the purpose of making that as passive interfcae instead of shut down.

your understanding is correct, however it means the interface will be included in routing updates sent via other active EIGRP interfaces which have neighbors formed. Passive interfaces will not send or process any updates because there is no neighbors to send to or receive from.

Just saw your post above and want to clarify your queries, Yes the updates are not sent on a passive interface but since you have advertised the subnets under the routing process that is why you will see those subnets in your routing table. If you still have some concerns please feel free to contact me on syedasifraza1@gmail.com

I was going through this post for my query . I understood that On passive interface the neighbors do not form adjacency but network are advertised. Why do the networks get advertise if it is a passive interface? In case of EIGRP, the Cisco document says that it does not advertise or receive packets /updates on that interface which is configured as passive. In my lab i had configured 3 routers with all the LAN interface as passive. I still got the routes of the lan on other routers from the respective Serial connections. Does Update not include network route update from the interface ? Its a bit confusing.

My answer to this is yes, these networks will be advertised to other EIGRP/OSPF neighbors.

Thanks for replying.

Request you to please clarify the below:

I go ahead and use the command passive-interface default and then in the next line i write no passive-interface Fa0, Im assuming that Fa0 is only interface now which can establish eigrp neighbors?? Will the network of Fa1 and Fa2 be learnt by the neighbors?????

The last part is eating my brains.. Will the eigrp/ospf neighbor know about the Fa1 and Fa2 networks?

Sorry to bug you, hope to see a reply soon

Your summary is exactly right

Thanks for your decent comment and please feel free to ask, request or comment anytime

Just to quickly summarize the above,

Say if we have three interfaces Fa0, Fa1 and Fa2, on a router running EIGRP/OSPF, considering in mind that these are interface specific protocols, meaning that we would use the network statement only if its present as a directly connected network to our router.

I go ahead and use the command passive-interface default and then in the next line i write no passive-interface Fa0, Im assuming that Fa0 is only interface now which can establish eigrp neighbors?? Will the network of Fa1 and Fa2 be learnt by the neighbors?????

By the way excellent posts – asusual