[c-nsp] MST and Uplinkfast

[Andy Saykao]

Hi Licoln,

We may have to do what you have suggested - thanks for the suggestion.

I labbed all this up today with mixed results. Basic access layer switch
with an access port (laptop pulgged into it) and two links out (one to
dist1-switch and one to dist2-switch). Each dist switch connecting to a
core switch. I then shut the primary link on the access switch to see
what happens to the access port. I also had a constant ping from the
core switch to the laptop.

Vanilla config on access switch:

interface GigabitEthernet1/0/1
 description Laptop plugged in
 switchport access vlan 2
 switchport mode access
 no ip address

Results:

2950
- PVST (access port stays forwarding)
- MST (access port goes through blk,list,lrn)
- IOS 12.1(22)EA8a

3750
- PVST (access port stays forwarding)
- MST (access port stays forwarding)
- IOS 12.1(19)EA1

3560
- PVST (untested but should stay forwarding)
- MST (access port goes through blk,list,lrn)
- IOS 12.2(40)SE

MST's uplinkfast implementation seems to behave differently depending on
which hardware platform you're using. If you've got 2950's and 3560's in
your network, you'll have to set the access ports to portfast and enable
bpduguard. No need to configure anything on the 3750's (although it
would be best practice to also define these access ports as edge ports).

Cheers.

Andy

-----Original Message-----
From: Lincoln Dale [mailto:ltd at cisco.com] 
Sent: Friday, 28 August 2009 12:07 PM
To: Andy Saykao
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] MST and Uplinkfast


On 28/08/2009, at 9:18 AM, Andy Saykao wrote:
> I have noticed that with MST and rapid failover that those ports which

> are not boundary ports or do not have portfast enabled go through the 
> blocking, listening and learning states again before forwarding.

whether its PVRST+ or MST used, you should always mark your 'edge'  
port correctly as being 'edge' such that they are operating as
"portfast" with "bpduguard".

it sounds like you have edge ports configured as "network" ports - so
the system HAS to wait for the "forwarding delay".
since you're saying that is 30 seconds not 15 seconds, that implies the
system is falling back to legacy (802.1D-2004) behavior.


cheers,

lincoln.

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