[c-nsp] Cisco trunk port startup delay

[Tóth András]

I would not encourage disabling STP at all, "portfast trunk" already
increases the chances of creating a loop, on the other hand it does allow
the port to transition to STP forwarding state immediately, so it should
have the same effect.

Given that the delay is due to the actual link down and likely re-ARP-ing,
the only option for further reduce the delay is to dual-home the servers,
preferably with a port-channel (etherchannel) such as 802.3ad LACP. That
will provide redundancy and sub-second failover if one member link goes
down or flaps.

Andras



On Fri, Jul 12, 2013 at 7:26 PM, Tom Storey <tom at snnap.net> wrote:

> If they are connecting to servers, do you really need spanning tree?
>
> I assume that spanning tree is blocking for x period of time, where x is
> long or short depending on whether portfast is enabled.
>
> If you remove spanning tree then there is no blocking, and it should come
> up and be able to pass traffic as quickly as MAC tables can update?
>
>
>
> On 11 July 2013 01:32, Shanawaz Batcha <ismath.shaan at gmail.com> wrote:
>
> > Hi Guys,
> >
> > Question for you is how soon can we get a cisco trunk port (connecting to
> > some enterprise servers) to initialize and pass traffic.
> >
> > From
> >
> > interface GigabitEthernet4/40
> >
> > switchport
> >
> > switchport trunk encapsulation dot1q
> >
> > switchport trunk native vlan 104
> >
> > switchport mode trunk
> >
> > spanning-tree bpduguard enable
> >
> > end
> >
> >
> > With the above configuration, we were losing about 50 pings for an
> if-down
> > event
> >
> > Enabling "portfast trunk" (no redundant connections), we lost somewhere
> > between 10 and 15 pings. Which is way better.
> >
> > Running "switchport nonegotiate" to disable DTP gives me another ~2
> seconds
> >
> > Disabling inline power and "disabling lldp" gives me another ~1 or 2
> > seconds
> >
> > We are still losing about 6 pings. Anything else people do/tune to get
> > quicker convergence if I may call it?
> >
> > Regards,
> > Shan
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