OSPF FR adjacency question
Here is a post that I sent in the past regarding this issue.
Even though the routers are “adjacent” they won’t become true neighbors with each other. By adjusting the hello/dead timers you can make any OSPF network type become adjacent but that doesn’t mean they will become
functioning OSPF neighbors.
OSPF network types that use a DR (broadcast and non-broadcast) can neighbor with each other and function properly. Likewise OSPF network types (point-to-point and point-to-multipoint) that do not use a DR can neighbor with each other and function properly. But if you mix DR types with non-DR types they will not function properly. You should see in the
OSPF database “Adv Router is not-reachable” messages when you’ve mixed DR and non-DR types.
Here is what will work:
Broadcast with Broadcast Non-broadcast with Non-broadcast Point-to-point with Point-to-point Point-to-multipoint with Point-to-multipoint Broadcast with Non-broadcast (adjust hello/dead timers) Point-to-point with Point-to-multipoint (adjust hello/dead timers)
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security) bdennis@internetworkexpert.com Internetwork Expert, Inc. http://www.InternetworkExpert.com Toll Free: 877-224-8987 Direct: 775-745-6404 (Outside the US and Canada)
—–Original Message—– From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Peter Cresswell Sent: Sunday, September 17, 2006 9:28 AM To: ccielab@groupstudy.com Subject: OSPF FR adjacency question
Hello all, I’m sure this question comes up all the time, but i’ve had a quick look through the archive and could find a previous posting. I’d like your opinion on the following scenario (hub & spoke over FR, single subnet): Hub / / Spoke1 Spoke2
- Hub has point-to-multipoint interface (in both ospf and FR and has FR broadcast to spokes) - Spokes have point-to-point interfaces (in both ospf and FR and has interface-dlci to hub)
By default this configuration will not build an adjacency because of different hello timers. Which of the following solutions (or others if you have them) do you think is the “prefered” way to set up OSPF adjancencies in this scenario?
1. Change hello time on both spokes to 30 secs. 2. Change hello time on hub to 10 secs. 3. Change the ospf network type on spokes to point-to-multipoint
Thanks,
Peter
Category: CCIE Study
