LOOPGUARD OVER POINT TO POINT WAN LINKS

[jeffreywatson]

So I have a question about loopguard over point to point WAN links

If at Site A we have Rtr-A to Switch A  ( Vlan 1)    OVER WAN   Switch B ( Vlan 1)  Rtr-B

I think we do have spanning tree enabled on the switch ports so one side is the root bridge.

There is more to the network than this - but the short story is that during a failover condition the point to point link

can become saturated for several minutes by multicast.And i have noticed that the Switch port puts the Switch A ports in LOOP INCONSISTENT  state  which it eventually recovers.

So I'm guessing we're temp not getting BPDU's back and forth.

Should I disable Spanning tree on the point to point links - or just disable loopguard or enable BPDU Filter ?

There are no other devices on the segment.

If SW A is the root port for the segment and stops receiving BPDUs for max age -  will it go into LOOP INCONSISTENT state also just like a non desig or Alt port will?

thank you

j

[paul driver]

Hello

Yes it will -

As SW-A is the root port so that will be one receiving the bpdus from SW-B Designated port as you so rightly stated

When the port stops receiving the bpdu, STP will think your network is loopfree and transition another alternate or backup port into a forwarding state thus loopguard will kick in on this root port as it will see the potential loop and put into an inconsistent state.

I wouldn't suggest disabling stp or removing loopguard, but maybe some storm control for multicast

res

Paul
  

[jeffreywatson]

Thank you

just curious but if these are point to point links then what benefit is loopguard?

I can understand leaving SPT enabled just in case.