MSTP, LACP (and possible UDLD?)
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Posted by Peter Eriksson on February 8, 2008, 11:55 am
Please log in for more thread options and I figured I'd do it _right_ this time and create a bit of redundancy and stuff. Anyway, I'm a bit confused right now... But first - our setup: Switch A - HP ProCurve 6200yl (K.12.57) Switch B - HP ProCurve 6200yl (K.12.57) Switch C - HP ProCurve 2900 ( Routing enabled in A and B. The 2900 in our main computer room. The idea is to configure them in a triangle - with primary links between C-A (4x1000Mbps) and B-C (4x1000Mbps) with a backup link A-B (1x1000Mbps) in case something goes wrong and to use MSTP to make sure the A-B backup link normally is "cut". The thing I'm a bit curious about is why STP only seems to block half (one direction) the A-B link (only one fiber link is used of the two we originally was thinking of using, the the second interface is administrative configured "down"): Router A # show span Trk2 ... | Prio | Designated Hello Port Type | Cost rity State | Bridge Time PtP Edge ----- --------- + --------- ----- ---------- + ------------- ----- --- ---- Trk2 | 20000 16 Forwarding | 001c2e-149f40 2 Yes No Router A # show int brief 3-4 Status and Counters - Port Status | Intrusion MDI Flow Bcast Port Type | Alert Enabled Status Mode Mode Ctrl Limit ------- --------- + --------- ------- ------ ---------- ----- ----- ------ 1-Trk2 1000SX | No Yes Up 1000FDx off 0 2-Trk2 | No No Down off 0 Router B # show span Trk1 ... | Prio | Designated Hello Port Type | Cost rity State | Bridge Time PtP Edge ----- --------- + --------- ----- ---------- + ------------- ----- --- ---- Trk2 | 20000 16 Blocking | 001c2e-149f40 2 Yes No Router B # show int brief 1-2 Status and Counters - Port Status | Intrusion MDI Flow Bcast Port Type | Alert Enabled Status Mode Mode Ctrl Limit -------- --------- + --------- ------- ------ ---------- ----- ----- ------ 1-Trk2 1000SX | No Yes Up 1000FDx off 0 2-Trk2 1000SX | No No Down 1000FDx off 0 The trunks are configured as LACP trunks. After a little while we seem to have a nice broadcast storm circulating in this one-way regulated ethernet highway :-) (So we right now keep both the interface "down" manually to break this loop). Relevant parts of the configuration from one of the routers/switches, A in this case - the others are configured similarly, in this one Trk1 is A-C and Trk2 is A-B (the backup link)): trunk 1-2 Trk2 LACP trunk 3-6 Trk1 LACP spanning-tree spanning-tree Trk1 priority 0 spanning-tree Trk2 priority 1 spanning-tree config-name "IFM/Core" spanning-tree config-revision 1 spanning-tree priority 1 A related question - is is a good or a bad idea to enable "link-keepalive" (UDLD) on the links that make up these trunks? - Peter -- -- Computer Systems Manager/BOFH Cell/GSM: +46 705 18 2786 Physics Department, Linköping University Room: Building F, F203 | |||||||||||||
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Posted by anoop on February 9, 2008, 10:47 am
Please log in for more thread options This doesn't make sense. xSTP works on both directions of a link. If a port is blocked, it should be blocking both incoming and outgoing traffic, regardless of the version of STP (STP/RSTP/MSTP). It might be a bug, or it might be due to your configuration, but I don't see anything obvious that was explain this behavior. You could try posting your query at: http://forums12.itrc.hp.com/service/forums/categoryhome.do?categoryId=269 > Router A # show span Trk2
> ... > | Prio | Designated Hello > Port Type | Cost rity State | Bridge Time PtP Edge > ----- --------- + --------- ----- ---------- + ------------- ----- --- ---- > Trk2 | 20000 16 Forwarding | 001c2e-149f40 2 Yes No > > Router A # show int brief 3-4 > > Status and Counters - Port Status > > | Intrusion MDI Flow Bcast > Port Type | Alert Enabled Status Mode Mode Ctrl Limit > ------- --------- + --------- ------- ------ ---------- ----- ----- ------ > 1-Trk2 1000SX | No Yes Up 1000FDx off 0 > 2-Trk2 | No No Down off 0 > > Router B # show span Trk1 > ... > | Prio | Designated Hello > Port Type | Cost rity State | Bridge Time PtP Edge > ----- --------- + --------- ----- ---------- + ------------- ----- --- ---- > Trk2 | 20000 16 Blocking | 001c2e-149f40 2 Yes No > > Router B # show int brief 1-2 > > Status and Counters - Port Status > > | Intrusion MDI Flow Bcast > Port Type | Alert Enabled Status Mode Mode Ctrl Limit > -------- --------- + --------- ------- ------ ---------- ----- ----- ------ > 1-Trk2 1000SX | No Yes Up 1000FDx off 0 > 2-Trk2 1000SX | No No Down 1000FDx off 0 > > The trunks are configured as LACP trunks. After a little while we seem > to have a nice broadcast storm circulating in this one-way regulated > ethernet highway :-) (So we right now keep both the interface "down" > manually to break this loop). > > Relevant parts of the configuration from one of the routers/switches, A > in this case - the others are configured similarly, in this one Trk1 > is A-C and Trk2 is A-B (the backup link)): > > trunk 1-2 Trk2 LACP > trunk 3-6 Trk1 LACP > spanning-tree > spanning-tree Trk1 priority 0 > spanning-tree Trk2 priority 1 > spanning-tree config-name "IFM/Core" > spanning-tree config-revision 1 > spanning-tree priority 1 > > A related question - is is a good or a bad idea to enable > "link-keepalive" (UDLD) on the links that make up these trunks? UDLD is typically used to detect "unidirectional links". If you think of the layered model, it runs below xSTP, so xSTP only considers a link up if UDLD reports that both directions are working fine. If your ports are directly connected and you are running LACP, I see marginal benefit in using this feature. It tends to be more useful if you have repeaters between the switches because then you have multiple hops between switches and a failure in one hop may not be seen by both switches, so having UDLD would help detect a problem immediately. Anoop | |||||||||||||
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> and I figured I'd do it _right_ this time and create a bit of
> redundancy and stuff. Anyway, I'm a bit confused right now...
>
> But first - our setup:
>
> Switch A - HP ProCurve 6200yl (K.12.57)
> Switch B - HP ProCurve 6200yl (K.12.57)
> Switch C - HP ProCurve 2900 (
>
> Routing enabled in A and B. The 2900 in our main computer room.
>
> The idea is to configure them in a triangle - with primary links between
> C-A (4x1000Mbps) and B-C (4x1000Mbps) with a backup link A-B (1x1000Mbps)
> in case something goes wrong and to use MSTP to make sure the A-B backup
> link normally is "cut".
>
> The thing I'm a bit curious about is why STP only seems to block
> half (one direction) the A-B link (only one fiber link is used of
> the two we originally was thinking of using, the the second interface
> is administrative configured "down"):