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STP Problem: Switch is seen on blocked link

Hi All

I have following situation:

Two Core Switches 4500 SW_C01 and SW_C02

and some Access Switches SW_A01 ...

The Access Switches are redundant connected to the two Core Switches. From the STP point of view we have a standard triangle situation.

Problem: Pinging the SW_A01 from SW_C02 is not possible.

more details: SW_C01 is root of the stp. On SW_A01, the uplink to the nonroot Coreswitch (which is SW_C02) is blocked (as it should). On the SW_C02 the sh arp tells me that the SW_A01 is connected directly on its own port, what is wrong, because this link is blocked at the other end. So why is the MAC-Address sean here?

Even more details:

The Core Switches are running PVST.

The Access Switch only supports CSTP.

How can I configure the Switches, that the Problem can be solved? Any hints?

Thanks much, Phil

1 REPLY
New Member

Re: STP Problem: Switch is seen on blocked link

For STP, what does SW_C02 say about the VLAN/IP Subnet that's not accessible? What does SW_A01 say? Do you have a STP root bridge conflict?

Where's the VLAN interface? You say you can't ping from SW_A01. Do you mean that you can't ping from the switch, or can't ping from a node attached to SW_A01? Do you have a VLAN interface on the switch? Can you ping each VLAN interface IP on each of the three switches?

If you unplug/shutdown the link from SW_A01 to SW_C01, can you ping SW_C02?

Are you doing any VLAN pruning? Do you have trunks properly configured and are you allowing all VLANs across?

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