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New Member

OSPF Instability between Cisco and 3Com Total Control hardware

I have a switched lan which has two Cisco routers, a 7513 and a 3600, along with 5 3Com Total Control 1000 chassis participating in an ospf area. All the units gracefully establish themselves with eachother. The problem occurs when there is any load spike on the 7513, or any interruption in the ethernet lan, reguardless of how brief. When this occurs the TC's get stuck in an EXSTART state with the Cisco hardware, requiring ospf to be restarted on the Cisco's to reestablish the ospf session. The TC's have even been known to just at random it seems drop into EXSTART. The two Cisco routers have no problems maintianing their sessions even with one router experiencing a load spike or a break in the lan between them, and the TC's don't seem to have issues establishing sessions amongst themselves, but getting them to interoperate is a hair pulling experience.

Cisco doc's suggest an MTU mismatch, however as all systems are on the same ethernet lan, MTU's should be 1500 across the board if I'm not mistaken. Suggestions on how to sniff out the cause and/or improve the robustness of the setup would be greatly appreciated.

4 REPLIES
New Member

Re: OSPF Instability between Cisco and 3Com Total Control hardwa

I have had a similar problem between 3Com Netbuilders and Cisco 3600 routers which was resolved by altering the RouterDeadTime parameter on the 3Com boxes. Hope this helps.

Purple

Re: OSPF Instability between Cisco and 3Com Total Control hardwa

It could be an MTU issue depending on how you have your routers tied to together , if you are using serial lines then and are running 12.X code then it will default the MTU size to 4470 and these must match on both ends of the line for ospf to work correctly . Do a show interface on all your connections that connect the routers together and make sure the MTU sizes match for all .

New Member

Re: OSPF Instability between Cisco and 3Com Total Control hardwa

Both Cisco's are running 12.0 code, and all hardware is connected via ethernet. There are two switches, both HP 4000's, one which has the Cisco's, and one which has the 3Com hardware. The two switches are linked via 100FDX ethernet. I show no errors on any interfaces, and we're not running vlans/etc above and beyond basic ethernet.

New Member

Re: OSPF Instability between Cisco and 3Com Total Control hardwa

Cisco router running OSPF may have problem on Broadcast MultiAccess Network (like Ethernet) if you are using device from different vendors because IOS use proprietary OSPF protocol to communicate with others OSPF device on the segment

OSPF standard does not define how OSPF work on Ethernet environment. Standard only defined NMBA and point-to-point environment. I would say that OSPF is the network topology dependence protocol.

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