OSPFv2 problems

RouterOS Forwarding Protocols
1

I’m having sporadic OSPFv2 problems over a wireless link (WDS, UBNT) between a 450G and a 1100AH. This happens on several of our links. The wireless links are very stable and do not drop any packets when the OSPF problem occurs.

Database Description packet has init bit set in middle of an exchange
OSPFv2 neighbor 100.42.32.10: state change from Full to 2-Way

So, the adjanceny comes right back after the drop, but it’s obviously causing connected routes to become unavailable which is a problem. Looking at the debug logs of this router, I can see:

Mar 29 08:51:52 router1 route,ospf,debug RECV: Database Description <- 100.92.32.86 on PER069-STP034-100.92.32.84/30 (100.92.32.85)
Mar 29 08:51:52 router1 route,ospf,debug,raw PACKET:
Mar 29 08:51:52 router1 route,ospf,debug,raw     45 C0 00 34 61 00 00 00 01 59 4E B2 64 2A 20 56
Mar 29 08:51:52 router1 route,ospf,debug,raw     64 2A 20 55 02 02 00 20 64 2A 20 0A 00 00 00 64
Mar 29 08:51:52 router1 route,ospf,debug,raw     31 59 00 00 00 00 00 00 00 00 00 00 05 DC 42 07
Mar 29 08:51:52 router1 route,ospf,debug,raw     00 00 00 09
Mar 29 08:51:52 router1 route,ospf,info Database Description packet has init bit set in middle of an exchange
Mar 29 08:51:52 router1 route,ospf,info OSPFv2 neighbor 100.92.32.10: state change from Full to 2-Way
Mar 29 08:51:52 router1 route,ospf,debug Originate Router LSA
Mar 29 08:51:52 router1 route,ospf,debug     area=area100
Mar 29 08:51:52 router1 route,ospf,debug Installing an LSA
Mar 29 08:51:52 router1 route,ospf,debug     lsa=Router LSA id=100.92.32.8 originator=100.42.32.8 seqnum=0x800068f7
Mar 29 08:51:52 router1 route,ospf,debug     old=Router LSA id=100.92.32.8 originator=100.42.32.8 seqnum=0x800068f6

I can’t seem to figure out what is causing this. We would prefer to to have to use NBMA.

Both sides are running 5.24.

Any suggestions would be greatly appreciated!

2

Hi..

If you have only two routers like point to point… Better to configure your router as AS NBMA.. that is will avoid any change it OSPF election structure

Hope fully its can be solve..

Meaning of full and two way its

Full mean Only DB (Designated router ) and BDR (Backup Designated router) can send or receive LSA from all routers

Two way mean the other routers in the OSPF domain only can send and receive LSA from DR or BDR routers..!!

Hope fully your problem be fixed once you change ot NBMA..!

Best regards
Ali Sami

MikroTik Authorize Trainer
MTCNA-MTCWE-MTCTCE-MTCRE-MTCINE

3

I would use OSPF point-to-point network type on this link. Also make sure you are running AirOS 5.5.2 or above on the Ubiquiti equipment (assuming it is M gear). AirOS 5.5.4 has been the best for OSPF on my network.

4

By PTP, you mean NBMA? These routers are all part of a “ring” architecture, so they each have two uplinks.

5

I should have said “these links”, sorry for not getting that edited correctly. Also I’m assuming that in your first post, you meant “We would prefer not to have to use NBMA.”

Sorry if I am explaining below your level of understanding. It’s not always apparent how much someone knows from a couple of short posts on the forum.

I mean links with 1 router on each end. There may be 500 links in your ring but each link may be 1 to 1 aka Point to Point.

In OSPF, point-to-point interfaces have two routers on the link, usually on a /30 network.

For two uplinks, across separate wireless or cabled links, at each site, you may have two physical interfaces talking to the two other sites. Each physical interface would be configured as a separate OSPF point-to-point network.

In OSPF, non-broadcast mutli-access interfaces have an unknown number of routers speaking on that network segment. However not every device would be able to hear the broadcast messages from every other device. Perhaps because one router is connected to an AP which has client-isolation enabled. All the routers connected to the client radios which connect to the AP are able to speak to the router behind the AP and no other routers. Therefore it matters which routers are “authoritative” on the network. Also most routers won’t see broadcast traffic from most other routers. Because broadcast messages don’t go everywhere you have to manually specify which IP addresses with which each router is supposed to try to communicate.

You can use OSPF NBMA interfaces on point-to-point networks, but you have to manually specify the IP address of the other router in each routers OSPF configuration. I prefer not have to hardcode more information than absolutely necessary into a router’s configuration. So, I try to avoid NBMA and go with point-to-point whenever possible.

Both NMBA and point-to-point work better than broadcast across wireless links. Which you choose to use is up to you. Just don’t use broadcast on wireless links. When the wireless links are UBNT M equipment, you want to be running 5.5.2 or more recent on the UBNT equipment. My MikroTik routers are running 5.21. I haven’t tried the stability of 5.24. It’s probably as good or better than 5.21. The UBNT firmware was the most critical variable on our network to maintain stability after we switched to using OSPF point-to-point interfaces. We tried NBMA and it worked well. It was just more items to configure.

If both uplinks were connected to the same physical interface you might need to use NBMA.

Clear as mud? :slight_smile:

6

Lambert,

Thanks for the detailed reply! Ok, It sounds like I need to try changing from “broadcast” to “point to point.” I’ll read up in the documentation and see what is required to make this work.

These are UBNT links and they are currently running 5.5.2. The routers are all 5.24 right now.

Thanks!