Justin, >> I have four switches (A, B, C & D) linked in a loop comprising 1Gbps >> fibre. Switch A is connected to a primary WAN router while switch C >> is connected to the secondary WAN router - the two routers working in >> a simple HSRP fail-over set. I want to ensure that this loop will >> survive the failure of any one link (e.g. if the link between A & B >> goes down, B will still be able to connect to the primary router via >> C & D.
>> I currently have the STP path costs set to A=4, B=5, C=6 and D=7 >> >> Question 1: Does this make sense? Should the "root bridge" (using >> Wikipedia terminology) always be the one connected to the primary WAN >> router? Does STP work well when the WAN uplink fails over to the >> secondary or doesn't it matter. Justin M. Streiner <[email protected]> responded > It's generally a good idea to set one switch to be your root bridge > (STP priority of 0). In your topology, the switch that is connected > to your primary WAN router would make the most sense. You can also > set a higher STP priority like 4096 on the switch that connects to your backup > WAN router. > You can set a higher spanning-tree link cost on the link between > C and D, and you really wouldn't need to set link costs on the others. > When the other switches run their STP calculations, they'll see two > paths to the root bridge, and one will have a higher path cost, so that > should go into a Blocked state and be listed as an alternate path. > You didn't say if you were running PVST/PVST+/rPVST/MST or > if you have VTP domains, etc. RSTP is running on A & B but C&D are too old. I'm about to upgrade C & D and they will run RSTP. No MST or VTP domains. We are looking to set up VLANs and separate out such as video (e.g. video conferencing) and low-priority back-up traffic in due course. >> Question 2: Should I set all non-uplink (interswitch) ports as "disabled"? > I think this might be worded somewhat backwards. Your inter-switch links > would be your uplinks. You need to run spanning-tree there. Cisco generally > doesn't allow spanning-tree to be disabled on specific ports. You can set them > as access ports in a specific VLAN if needed, and run portfast. DO NOT run > portfast on trunk ports. I think newer versions of IOS will yell at you if you > try to do this, but in older versions, it was a great way to create bridging loops :( I will run portfast on all non-fibre ports (Fibre is only used for the inter-switch links). > jms Many thanks for the above. Chris _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
