I'm setting up a new small backbone network (and edges too, partly) 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