Connecting Straight cable between Switches

[Pavan T L]

we have redundant 2610 switches.we have done an test for checking failure mode of switches.

configuration

1. port 1 & 2 of both switches are configured as Trunk with LACP.

2.Broadcast Limit of all ports are set to ZERO.

3. In both switch 2 ports (7th and 8th port) are configured as AUTO mode and remaining ports are kept at MDIX mode and Ethernet straight-thru cable were connected to the 2 ports (7th and 8th port).

observation:
After connecting staight-thru cables switches were not working.we were not able to communicate with the machines which were connected on same switch.

Please can u tell, by following the above configuration what happens to switch and why the switches are not working??

[Mohammed Faiz]

If you disable broadcasts won't that mean the machines won't be able to use arp to discover each others MAC addresses?

[Pavan T L]

As far as I understand disabling Brodcast Limit mean, consdier if a port is configured for 100 mbps full duplex, Port can brodadcast upto full 100 mbps.

If we enable Broadcast limit say 1 % broadcast will be throttled to 1 mbps

it is not relate to arp to discover each others MAC addresses.

[Mohammed Faiz]

Ah, I misread the manual. I thought is said that settting a broadcast limit of 0 disables broadcasts but it just disables the feature.
What version of code are you running? I've just remebered there was a bug with the mdix settings on the early 2610 code.

[Richard Brodie_1]

You configured port 1 and 2 as a trunk on both switches, then connected port 7 to port 7 and port 8 to port 8?

[Pavan T L]

Hi Richard,

Port 1and 2 are trunk and it is connected with cross over cable.

one of our customer had made mistake and they have connected straight-thru cable between the 2 ports of the switches and communication was stopped.. even the machines on same swith was not able to communicate.

Just i want know what happens to switch if we connect straight-thru cable between the ports of the switch ???

[Drew Redman]

If you already have the switches connected to each other via a trunk, and then you add another link between them that is not part of the trunk, you are creating a redundant path in the network and will cause a broadcast storm, which is probably what caused you to lose connectivity.

Either add ports 7 & 8 to the existing trunk, or enable spanning tree so 7 & 8 are blocked unless the trunk goes down.

Auto MDIX is recommended. Setting the port on each side to be the same as the other side (either MDI or MDI-X) will require a crossover cable in order to get link.