[c-nsp] MST/IEEE 802.1s - adding a VLAN will impact traffic forwarding ?

[Mark Zipp]

Hi,

I'm wondering if anybody has an update or any fresher opinions on the
the following thread, regarding having to try to synchronise MST VLAN
additions/removes on multiple devices at once to try to avoid
impacting traffic forwarding for existing VLANs. We're about to face
the same problem, and I'm wondering if Steinar Haug's advice to use
Rapid PVST is still valid. I'd expect we'd be running 50 to 100 VLANs
over the exact same physical topology, so using MST is attractive.
After googling a bit, I can't seem to find much advice that says "this
is how you add or delete VLANs this in a production MST environment
without impacting traffic"

>From Andrew Fort,

"...

 From this rather green viewpoint, it appears to boil down to making the
changes (doing moves/adds/changes on vlan->instance mappings) on all
switches in the given MSTP region at the same time (i.e., having lots of
vty sessions open), then (preferably) verifying all pending configs
match ('show pending') and then sending 'exit'/^z/^c/etc to all devices
at close enough to the same time so that you hopefully don't change your
L2 forwarding paths away from the desired for too long.

..."

http://puck.nether.net/pipermail/cisco-nsp/2003-November/006854.html

and the reply from Steinar Haug,

"After some lab testing of MSTP we concluded that we would need *much*
more testing to be comfortable with MSTP and all the corner cases. We
also concluded that the MSTP implementation needed to mature a bit.

Rapid PVST, on the other hand, seems to work well for us, and we are
using it on all new 3550s and 6500s that we install. Obviously doesn't
scale as well as MSTP."

http://puck.nether.net/pipermail/cisco-nsp/2003-November/006868.html

Thanks in advance,
Mark.