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3COM 4924 beteen two 1750's halts HSRP


We have inherited a customer network as below.




3COM 4924




The 1750 router - call it A1 - is the main FR link to site, and the 1750 router - call it B1 - is the ISDN backup. The link between the two is a flat layer 2 (VLAN 1) network. Access layer device is a single 3COM 4924 switch.

I can get to A1 via the main frame link, but I can't access B1 from A1 when the switch is in place. Bypass the switch with a crossover cable between A1 and B1 and connectivity is restored. Pretty damning really for the 3COM! When the switch is in place , the HRSP standby group does not stand up between the two routers, I can't telnet to B1 from A1 (but can ping it). I have debugged HSRP and I can see outbound Hello messages leaving A1, but no Hello messages inbound. CDP is working and I can see full B1 details from A1.

The switch support company has stated that it is not a fault with the switch as they have reportedly been swapped out twice already, but the fault remains the same.

It must be the switch at fault, or some incompatibility between 3COM and Cisco kit. We had trouble getting the switch to see teh speed and duplex when the 1750 was hard set to 100 full.

Has anybody seen any documents or have any experience on 3COM/ Cisco interoperability issues? Replacing the 3COM with a 24 port Cisco switch is unfortunately out of the question :(

Cheers guys



Re: 3COM 4924 beteen two 1750's halts HSRP

could be almost anything it looks like the 3 com is a full l2/l3 switch if it is supposed to just be a layer 2 switch then you have to make sure the connecting ports are just normal ports and not routed ports , make sure routing is turned off and both connections are int he same vlan . Don't know 3coms so just some things to verify , may have to go to the 3com site and see how to configure those switches to do what you want. 3com info

Community Member

Re: 3COM 4924 beteen two 1750's halts HSRP

Thanks Glen,

Unfortunately, I don't control the switches - just the routers for this customer.

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