Spanning Tree vlan question

[paul amaral]

Hi, I have a cisco 6509 that is the root bridge doing rapid PVST and a bunch of connected 3524XL switches doing the default IEEE spanning tree protocol. On the 6500 all connected 3500 switch ports are part of vlan 150 however on the 3500 i only have the default vlan1 setup. I have this setup for awhile and it seems to be working fine, however something doesn't look right and im wondering if i should have all ports on the 3500 part of vlan150. This seem to be working but I'm asking if what im doing is correct and does it matter that im running PVST on the 6500 but only have vlan1 configured on the 3500 switches.

thanks paul.

[Mohamed Sobair]

Paul,

it doesnt matter as long as the RSTP is fully compatible with PVST+, the 6500 will revert back to PVST when communicating with the 3500 catalyst.

However, it would be better to have all switches operates in RSTP mode if they support it to benefit from the Convergence speed that RSTP provides.

Regards,

Mohamed

[Jon Marshall]

Paul

If your ports on the 3500s are in vlan 1 but your switchports on the 6500 switches that the 3500 switches connect to are in vlan 150 then you have effectively joined the 2 vlans. You really don't want this.

If the above is correct then i recommend you either change the switchports to vlan 1 or the ports on the 3500 switches to be in vlan 150. It depends on which vlan or more specifically subnet you want the ports on the 3500s to be in.

Perhaps you give some more details before making changes.

Jon

[paul amaral]

Jon, I agree that I should keep them separate and usually thats the case, its just that i had this setup for so long without revisiting it and just recently notice the vlan settings. The interfaces on the 6500 that connect to the 3500 are part of vlan150 and vlan150 with a SVI interface with multiple ip addresses, 10.10.10.x/24 is used for the management ips for the 3500's. Off the 3500s i have PCs/servers with other ip/subnets.

Again things seem to be working without issue I just wanted to know what if there is any negative issues that can arise from this. I'm assuming because I have no trunks between the switches, all ports are set to default switchport, that the vlan settings don't even come into play, is this correct?

Mohamed, The 3500 are sunning RSTP and although the 6500 is configured for rapid-PVST it lists rstp when doing a show spanning tree on the 6500. FYI

thanks guys!

paul