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Rapid STP in the WAN?

Scenario...

11 switches in a loop. Total distance of the loop is 200 miles (not sure that the distance matters...). Point to point connections between switches. 1 / \\ / \\ / \\ 11 2 / \\ / \\ / \\ 10 3 / \\ / \\ / \\ 9 4 \\ / \\ / \\ / 8 5 \\ / \\ / \\ / 7---X---6

1 is root, break in the loop occurs between 6 and 7.

Side question: reading RSTP documents, it appears the recommended number of bridges in an STP instance is 7. Is this 7 from the ROOT or 7 END-TO-END?

Anyway, Now suppose a few "spurs" are introduced into the topology, connected to switches 6 and 7...spur 1 and spur 2 are effectively 13 hops from each other and 230 miles or so.

1 / \\ / \\ / \\ 11 2 / \\ / \\ / \\ 10 3 / \\ / \\ / \\ 9 4 \\ / \\ / \\ / 8 5 \\ / \\ / \\ / 7---X---6 / \\ / \\ spur1 spur2

I'm not a great spanning-tree mind, but this seems like a disaster waiting to happen.

Am I wrong? Are there ways to tune RSTP to make this dream a reality?

Reply to
wayne
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Are there ways to tune RSTP to make this dream a reality?

yes disable it

STP/RSTP is a distributed virus

Reply to
Merv

You are preaching to the choir.

However, this has been presented as an option by a VAR and management is seriously considering it since it's the LOWEST BID! It's a MetroE/QinQ solution with ME3400 switches.

ug.

I'm recommending a different bid that is a routed VRF-lite network using

3560E switches (there are multiple networks that need isolation yet run over the same physical infrastructure).

There is one VLAN that needs to be dropped at multiple locations, that one can be tunneled, or we can just deal with RSTP on the one VLAN, it's not that important anyway.

Reply to
wayne

YeahI can just see what is going to start happening with Metro Ethernet - companies will start building flat networks again just like they did when VLAN switches appeared...

And then the mop-up operation starts all over again ...

Reply to
Merv

3400s understand IP routing....
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look in the config guide. reads like a 3560 but without VRFs.

if you have L3 devices at each site, ask for dual interfaces, or separate pt - pt VLANs, and do the topology bit yourself?

a spanning tree storm will melt either complete links, or the entire set of switches - so you probably do care.....

Reply to
stephen

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Depends on the image. METROIPACCESS yes, METROACCESS and METROBASE, no. The proposal had METROACCESS in the WAN, with L3 devices connected to QinQ ports on the WAN switches.

You are right, good point.

For what it's worth, I talked to my immediate supervisor and explained my concerns with the low bid, he agreed and will bring it up with the Deciders.

Reply to
wayne

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