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Community Member

LAN Connectivity Issue

We have a 3750 configured as a gateway, with gig connections to several client switches (all 2950).  Recently, we discovered that one of the switches has an additional connection to the core switch into one of the ethernet ports.  If we remove either of the cables, all of the switches connected to the core switch lose connectivity.  I have moved all four ports, and it does not seem to matter, so I don't believe it's related to any particular port.  The only thing I can think of offhand is that it may have something to do with STP, but am not able to determine enough to change anything.  Looking for any sort of help here!

Configs of the core switch and the switch with the two connections are attached.  The ports in question are Fa0/4 and Gi0/2 on the 2950 and Gi1/0/2 and Gi1/0/33 on the 3750.


Thanks in advance!


Hi, By looking at your



By looking at your configurations..... the connection between 2950 and 3750 using the default interface shouldn't have any problem...... bcos it will be taking the VLAN 1 as default..... but the other interface with vlan 2 on core and default vlan on 2950, where i am thinking might have the problem..... also the other switches has the gateway address or route pointed to core switch vlan ip or other? If gw of other switches is the 2950 then it might have the connection issues....




Community Member

I think its STP issue only. I

I think its STP issue only. I think your old 2950 is elected as a root bridge, as it has a older MAC address than 3750, Please try to find out root bridge for your network.

# show spanning-tree vlan 2


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