andrew_2706
asked on
Problem Connecting Cisco 3750 switch to SG200
We've recently moved a switch stack for a customer and are having some difficulties with connecting some Cisco switches together.
There are 2 core switch stacks made up of 1 x 3750X and a 3750G (4 x fibre links between)
Off one of the core stacks there are then 2 more stacks hung off that with a series of about 4 3750's in each stack.
When I connect a Cisco Small Business Series SG200 switch to anywhere in the stack (which is doing L3/VLAN routing) the port goes into error mode. The guy who configured the switches said it would not be possible to connect the 2 types of switches as they were not designed to connect together, and he enabled something to error the ports when they were connected as without that it killed the whole stack due to a spanning tree election or something. Sadly I don't know enough about them to know the problem, but I see from another post that someone else is in fact using the two series of switches together with success here,
https://supportforums.cisco.com/discussion/11275351/help-setting-multiple-subnets
Any ideas?
There are 2 core switch stacks made up of 1 x 3750X and a 3750G (4 x fibre links between)
Off one of the core stacks there are then 2 more stacks hung off that with a series of about 4 3750's in each stack.
When I connect a Cisco Small Business Series SG200 switch to anywhere in the stack (which is doing L3/VLAN routing) the port goes into error mode. The guy who configured the switches said it would not be possible to connect the 2 types of switches as they were not designed to connect together, and he enabled something to error the ports when they were connected as without that it killed the whole stack due to a spanning tree election or something. Sadly I don't know enough about them to know the problem, but I see from another post that someone else is in fact using the two series of switches together with success here,
https://supportforums.cisco.com/discussion/11275351/help-setting-multiple-subnets
Any ideas?
ASKER
We had an instance before on this network where we plugged in an SG200 (with a completely default configuration) and it killed the entire network of switches because it caused a span tree election/error, do you know what this might have been. I'm concerned about removing the bpduguard (he did say he was enabling something guard to prevent the problem) as I don't want the network to die again, it was horrible!
If there was STP loop it could kill the whole network down, but than that would mean that spanning tree had some error in configuration or was disabled on ports.
You should not remove bpduguard just because I told you. I don't know your configuration, it is just my guess, but than again, my guess is just "configured" from your description and you are not sure what really happened. So, don't touch anything. bpduguard should kill port instantly and protect network from what you describe now.
STP election should last about 50 seconds, but for that time network could be completely down. But without more details (switch configurations) it is hard to be sure about root cause.
You should not remove bpduguard just because I told you. I don't know your configuration, it is just my guess, but than again, my guess is just "configured" from your description and you are not sure what really happened. So, don't touch anything. bpduguard should kill port instantly and protect network from what you describe now.
STP election should last about 50 seconds, but for that time network could be completely down. But without more details (switch configurations) it is hard to be sure about root cause.
ASKER
I definitely wouldn't have turned it off during the day, i'd get shot if it all fell over!
A loop would imply like a network look I guess, but there was only one cable from the 3750 to the sg200 with absolutely nothing else connected which was very confusing.
A loop would imply like a network look I guess, but there was only one cable from the 3750 to the sg200 with absolutely nothing else connected which was very confusing.
Let me just say that beside some STP issue, VTP also could kill whole network that way if VTP revision number on SG200 was bigger than VTP revision number on Cat 3750, it would replace vlan database on 3750 with SG200 vlan database, and many (or all) lights on switches would be amber.
ASKER
That sounds very familiar from what the guy setting the Cisco switches up, the revision was higher by default and he wasn't aware of how it could be changed, do you know if its possible to change the setting in the SG200 series?
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Most likely is that your Cat3750 switches are configured with bpduguard on ports where SG200 was connected, so it would, as soon as BPDU that SG200 send is received on Cat 3750 port - set port in error-disabled state. So, I guess that he just removed bpduguard from port.