[c-nsp] spanning-tree for local switching on ASR920

Gert Doering gert at greenie.muc.de
Thu Oct 19 05:14:39 EDT 2017


On Thu, Oct 19, 2017 at 09:45:08AM +0100, adamv0025 at netconsultings.com wrote:
> Hmm and if you enable debug can you actually see the stp packets being
> issued (or even received) on either of the ports?
> The config looks good for catching and processing such PDUs. 

It's not sending PDUs, so the receiving end has nothing to work with.

If I connect both links to a switch that has STP active, and change the 
l2proto to "l2proto forward stp", the *switch* will stp-disable one 
link, but the ASR920 never does anything with it (except eat the STP
packets if "l2proto peer stp" is set).

> Btw I'm still not getting the setup, so you have FW1 in port 1 and FW2 in
> port 2 and p1 and p2 are in BD1.

In that case, there won't be a loop.  But customers are creative in cabling,
so I want to ensure that if the customer connects p1-p2, or connects a
switch that loops things around, the setup will not start looping packets
(... it is a local loop, and the ASR920 can stand it, but it might break
stuff in the customer network, and then we get to fix it "because your
device did it!").

Of course, split-horizon would also achieve this, so I'm not desperate to
find a solution for this particular use case - I just want to find out
whether STP can be done or not.

Seems I need 16.6 fanciness for that, which we'll try.


USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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