Comware

Hello All,

I am trying to set up a redundant core (layer 2, 5406 with RSTP), 2 sets of distribution switches (2x3500 at two different buildings, set up as layer 3, ospf, with VRRP). In each building there are 8 to 10 edge switches (2600s) and each of these edge switches is uplinked to each of the two 3500 distribution switch, with ip default gateway on edge switches to be the VRRP owner IP of device management VLAN.

The two 3500s at each location are uplinked via a single gig fiber each to the each of the two core and two 3500s have two copper gig ports connecting each other.

I have a VLAN set up on all the switches in a single subnet for devices management. This VLAN is forbidden on the trunks between the two 3500s, but is tagged on all other switch to switch connections. Each of the building 3500s and 2600s are set up with MST in its own unique region (config revision) and all of these 3500s then run ospf between each other via core, which runs RSTP to glue them together.

I am running into ospf adjacency issues (though it seems like all 3500 uplinks, with ospf VLANs tagged on them and created on 3500s and 5400s, it should be simple layer 2 interconnection). In one building, I find the trunk between the two 3500 to be blocked and all uplinks from these 3500 to the core to be forwarding, while on the other building, trunk between 3500s remain forwarding and some of the uplinks to core then blocked, basically to avoid loop. I will like to have the trunks between the 3500s at both buildings to be blocked (when all uplinks are intact), so that all 3500s can form adjacency with all others. I have tried manually assigning higher cost to the trunk between the 3500s, but at one building, it will always stay forwarding, while at other building it will always remain blocked. This is causing issues as only three of the four 3500 then form adjacency, while relations with fourth are stuck in either exstart or 2way.

Can someone post some relevant spanning tree (MST on edge and distribution layer switches and RSTP between distribution and layer 2 cores) configuration for this kind of common scenario?

Thanks

Do you have network map you could attach here?

It sounds like you're running into a problem where MSTP is blocking some of your OSPF links.

Usually one would disable spanning-tree on any of your point-to-point routed links.

I have attached a quick network diagram of my proposed setup. I have tagged VLAN100, the device management vlan on all uplinks except the trunk between the L3 switches. VLAN 50 & 60 are for ospf links between L3 switches via core switches. Core switches have only VLAN50, 60 and 100 created.

Please advise.

Thanks