cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
791
Views
0
Helpful
2
Replies

OSPF Adjacency

tahir1234
Level 1
Level 1

Hi serniors,

I have Lan/Wan setup in my office with Cisco routers & switches. OSPF is running on serial as well as multiaccess network. Yesterday I noticed that 2 routers changed adjacency from FULL/DROTHER to 2WAY/DROTHER. Network is running fine without any outage and impact. Later I noticed that a switch is installed on both of these routers interface that changed the adjacency but switch ports are up and running. My question is

  • why routers changed the OSPF adjacency ?

Thanks.

Tahir.

2 Replies 2

Reza Sharifi
Hall of Fame
Hall of Fame

Hi Thair,

Did you add another router connecting to you current 2 routers using the same subnet.

This usually happens when you have 3 or more routers on the same subnet, one route is Designated Router (DR) and one Backup Designated Router (BDR). All other routers have a two-way adjacency established. This is normal behavior for OSPF.

http://www.ciscosystems.net.ph/en/US/tech/tk365/technologies_tech_note09186a0080094059.shtml#routers

HTH

Reza

hi

Nothing was added in that particular network. In that particular network there are 8 routers on the multiaccess network and definately on some segments there are DR and on the other therer are BDR. Routers have FULL/DR and FULL/BDR adjacency on other ports but on a certain port (as i told before) , the adjacency was FULL/DROTHER that changed to 2WAY/DROTHER. My concern is that "WHAT caused this change?" Moreover when i see the router logs , it displays that adjacency changed from full to 2way & when i run "show cdp neighbor" on both routers , neither is in the cdp neighbor list while they are connected. No one changed the priority on the routers as well.

Thanks.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Innovations in Cisco Full Stack Observability - A new webinar from Cisco