Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

STP Problem 2

Good Day!

i am now trying to configure 2 more switches having this topology:

2 - 6509 (1 and 2)

2 - 3548 (3 and 4)

2 - 2950-24 (5 and 6)

1-->2-->3-->4-->5-->6-->3 and 1-->4

1-->2 trunk

2-->3 trunk

3-->4 gigastack (trunk)

4-->5 vlan 4

5-->6 FE trunk

3-->6 vlan 4

1-->4 trunk

native VLAN: 1

Problem: cannot ping interface vlan from laptop connected to 6.

Comments highly appreciated.




New Member

Re: STP Problem 2

Hello Ian,

It looks as though on switches 4, 5 and 6 only vlan 4 traffic would have access to the rest of your network. With the trunk between switch 5 and 6, I assume you have other vlans on both switches? Those vlans would not have access to the rest of your network, due to the link between 4 and 5 and the link between 3 and 6 only carry vlan 4.



Re: STP Problem 2


What Murph said.




[visualize vertical lines here indicating trunk connections between 6509 above, and 3548 directly below; hard to really draw vertically here]






[visualize vertical lines here indicating VLAN 4 connections between 3548 above, and 2950-24 below]






[visualize vertical line here, connecting 2950-24(6) to laptop below]




Native VLAN is 1, only matters on VLAN trunk ports.

Assuming that VLAN 4 is the only VLAN on those two links between 3548s and 2950-24s, then those connections are VLAN access links, not VLAN trunk links. (Or, they could be VLAN trunks with all but VLAN 4 pruned off.) I guess you could think of them as "VLAN-4-only" trunks.

But VLAN 1 on the 2950-24s is isolated from VLAN 1 on the 6509s and 3548s. Not sure which interface VLAN you're trying to get through to, but I guess it's on or via the 6509s, they're the only devices capable of routing IP.

You either need to string a separate and parallel VLAN 1 connection next to each of those VLAN-4-only connections; or turn those VLAN 4 lines into VLAN trunks. Then it should work.

Is this the same network we were talking about in previous "STP Problem " post? Looks kinda similar in layout, but the bottom switches are different model...

CreatePlease to create content