(Rapid) Spanning Tree Protocol Questions

In our case the DSLAM is a very basic switch. Supports ethernet switching and VLANS inc VLAN priority bits. The trunk port is physically a optical gigabit ethernet port.

As far as switching goes it has a system wide ARP table containing customer MACs & ports to Upstream MACs via trunk port.

I am still trying to understand the advantage of the DSLAM support STP. Typically DSLAMs are only connected to a single Switch (sometimes in the same location, other times a few streets away). The resiliance is always in the metro ethernet.

This customer is the first to consider connecting the DLSAM to 2 switches (I guess this is why the want STP support).

Thanks,

R

This is a funny one but there are a few things we can establish. First, if your DSLAM is connected to just one downhaul switch then regardless of whether or not it supports STP it can't become the root bridge anyway, so no problem there.
Second, if this customer is going on about STP at all then their only reason for wanting to connect the DSLAM to two backhaul switches must be for redundancy of the connection - with two layer 2 links, STP will block one of them so that only one is actually in use. The key question here then is does your DSLAM support STP on the backhaul ports or does it not? And I think the easiest way to check that is to have a flick through the manual. If you haven't got any documentation then log on to the thing and look for menu or command options that relate to it. If the thing does support STP (or RSTP, similar but different) then there are a couple of things we can tweak to make to very unlikely that it ever becomes root bridge. Then you tell your customer what you've done and say something like as long as you don't exceed this priority I guarantee my device will never become root.

I've been following this thread, and from a theoretical standpoint, it is interesting, but at the end of the day it doesn't really matter-

Your network stops at the CPE. His network starts at the CPE. He can do whatever he wants on _his_ network.

A customer should never be allowed to become the root bridge for _your_ network, which is what this guy is asking you to do, as it removes spanning-tree control from you and gives it to him.

So Ranger24, is this customer the upstream switch provider that is suggesting the redundant links, or a CPE customer? I'm a bit confused.

Hi Guys,

My DSLAM connects my customer's end users to his network as follows

EU-PC -->CPE-->DSLAM-->MetroNet -->BRAS -->ISP/WWW

EC-PC = End User PC
BRAS = Broadband Remote Access Server (Authentication)

The network from the DSL port of the CPE to the ISP is owned by my customer. I supply the DSLAM & BRAS.

From comments made I can't see yet an advantage of anyones DSLAM supporting STP. STP only seems to be an advantage for the MetroNet.

When designing the DSLAM STP was discounted as we couldn't see the advantage. When you consider the traffic loads running on a typical DSLAM it doesn't make sense for it to take any additional load by becoming a root bridge.

All operators I work with across europe ensure resilency and load sharing is the responsibility of the metronet.

Hope this makes it clearer!

R