Help with switch configuration, ( 3 3550's, 5 2950's end to end )

I am connecting via fiber 8 switches out on a Texas railway. It looks like
this:

3550-2950-2950-2950-3550-2950-2950-3550 <-- then this 3550 has another pair
going straight back to the 1st 3550, to create a redundant path.

That is an 8 switch diameter, and concerned with STP. The 3550's have EMI
images so I have flexibility there. What would you recommend for this as far
as configuration? My goal is that if any fiber link and/or switch breaks, an
alt path exists. Since STP diameter is large than 7 I suppose I cannot just
rely on layer 2 and should break these up into layer 3 somehow?

 

["ec"]

| That is an 8 switch diameter, and concerned with STP. The 3550's have EMI
| images so I have flexibility there. What would you recommend for this as far
| as configuration? My goal is that if any fiber link and/or switch breaks, an
| alt path exists. Since STP diameter is large than 7 I suppose I cannot just
| rely on layer 2 and should break these up into layer 3 somehow?

Layer 3 is often a good choice. You may also want to look into Rapid
Spanning Tree (RSTP, 802.1w) which doesn't have the 7 hop limit of
standard 802.1d STP - and also gives you much faster rerouting.

Cisco Per-VLAN RSTP is a breeze to configure (just turn it on) as long as
all the switches support it.

Steinar Haug, Nethelp consulting,

 

Damn, spanning-tree mode rapid is your friend! Thanks, I never knew 2950G
supported per vlan rapid-stp. Cisco docs say it doesn't, but the command is
there and it does work. What are the limitations of RSTP?

 

Hi ,

Can you refer me to resource or url of this comment : ( 802.1w does not have 7 hop limit)

--------quote----------
Layer 3 is often a good choice. You may also want to look into Rapid
Spanning Tree (RSTP, 802.1w) which doesn't have the 7 hop limit of
standard 802.1d STP - and also gives you much faster rerouting.


Thanks