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I have a simple star network setup, a core HP switch with servers and storage, and WAN uplinks on it, and then trunked 2 x 1GB uplinks to some crappy old Netgear switches (I know, but moving on).

We recently had a network storm. After some invesigation we found the loop-protect features of the HP, but this seems to be for edge ports only. We then realised that perhaps what we should do is have spanning tree enabled, and so my question is about how best to do this.

I understand that the core switch should be set up as the bridge with priority 0, and I'm assuming that the Netgear trunked uplinks need to be set up as something like a priority 4, but is this right or do I only set the Netgear trunk priority on the Netgears and not on the HP? The edge switches only know about two VLANs, 1 (normal) and 3 (guest wifi).

Quick diagram:

The top half of the diagram is what's in the central rack, the bottom half is the 'edge'.

Config snippet follows:

trunk B3,D3 trk3 trunk
trunk B4,D4 trk4 trunk
trunk B5,D5 trk5 lacp
trunk B6,D6 trk6 trunk
trunk B7,D7 trk7 trunk
trunk B8,D8 trk8 trunk
trunk B9,D9 trk9 trunk
trunk B10,D10 trk10 trunk
trunk B11,D11 trk11 trunk
trunk B12,D12 trk12 trunk
trunk C19,D1 trk13 lacp
trunk A21,E11 trk17 lacp
trunk A19,E17 trk18 lacp
vlan 1
   name "DEFAULT_VLAN"
   no untagged A3-A6,A15-A18,A20,A23-A24,B2,C3-C6,C13-C18,C20,C23-
C24,D2,D21,D23,E2-E4,E13-E16,E18,E22-E24,F5-F6,F8,F10,F12-F15,F17-F21,F23-    
F24,Trk13,Trk18

   untagged A1-A2,A7-A14,A22,B1,B13-B24,C1-C2,C7-C12,C21-C22,D13-
D20,D22,D24,E1,E5-E10,E12,E19-E21,F1-F4,F7,F9,F11,F16,F22,Trk3-Trk12,Trk17

   ip address xxxxx
   ip igmp
   exit
vlan 2
   name "SAN"
   untagged A3-A6,A15-A18,A20,B2,C3-C6,C13-C18,C20,D2,E2-E4,E13-
E16,E18,E22,F5-F6,F8,F10,F12-F15,F17-F21,Trk13,Trk18
   ip address 192.168.7.1 255.255.255.0
   jumbo
   exit
vlan 3
   name "WiFi"
   untagged D23
   tagged A1-A2,A7,A9-A11,B19,C2,C7-C10,C12,E1,E5-E8,F3-F4,F9,F11,F16,Trk3-    
Trk11
   ip address 192.168.15.2 255.255.255.0
      exit

So my real question is - should I enable spanning tree, and if so... how?

I know I can do this:

spanning-tree priority 0
spanning-tree Trk3 priority 1 path-cost 4

and this:

spanning-tree B3,D3 priority 1 path-cost 4

But should I?

  • Should you enable STP? Yes. Should the HP switch be the root bridge? Probably. That being said, if your diagram is an accurate representation of the inter-switch connections, I don't see a physical loop in your network. What was the nature of this network storm and how did you determine that there was a network storm? – joeqwerty Jun 23 '15 at 13:23
  • Someone essentially connected two ports on an edge switch. It brought down the entire network. – SteveDolphin23 Jun 24 '15 at 13:26
  • OK, understood. A Switch loop will bring a network to it's knees pretty quickly. STP definitely would have prevented that. It's considered best practice to enable STP even if you only have one switch. – joeqwerty Jun 24 '15 at 14:57

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