Forum Discussion
BranoZ_101205
Nimbostratus
Nimbostratusinteroperability with Per-Vlan RSTP
Hi,
I have LTMs connected to Cisco L2 cloud with mandatory Per-Vlan Rapid STP (PVRST). How should be STP configured on LTMs with minimal impact L2 stability ?
Each LTM is connected with two-link trunk to two Cisco switches (see attached topology). There are multiple VLANs on each trunk. Those Vlan have _different_ L2 topologies. The EtherChannel interface on Cisco is configured as if connected to other switch:
spanning-tree mode rapid-pvst
interface Port-channel2
description ltm02 trunk
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 411,413-415,459
switchport mode trunk
spanning-tree cost 100
end
The problem here is that LTMs don't support PVRST. Currently it is configured for STP (for historical reasons). The problem that happened to me twice in last few months was that the L2 loops were created after major failures (topology changes). Last time the LTM-Cisco trunk was part of the loop and STP stabilized immediately after the trunk was brought down. I'm not completely sure LTM is to blame, but I cannot rule it out either..
Looking at the supported STP modes, "pass-through" looks like the best candidate in case the rest of the network speaks PVRST.
Any recommendations ?
John_Heyer_4582According to Cisco, RPVST should be backwards compatible with RSTP. However, when I try to set STP on the LTM, it just acts as a transparent bridge. It never sees the STP root (which is directly attached) and never puts any ports in blocking state. Instead, that is done by one of the Cisco switches.
I'd be curious how things would work with MSTP....
jason_57094I get the same outcome. I have a similar situation with 2 F5's and 2 Cisco 6513's running rapid-pvst and no matter what I try, the F5's don't see the other switches, always put all their links in forwarding state ( designated ) and think they are the root bridge.
satish_txt_2254Cirrus
what is the workaround of it? what mode we should use on F5 ?