[c-nsp] Cisco trunk port startup delay

[Shanawaz Batcha]

Thanks for the suggestions.

* I am definitely not disabling spanning-tree. I have enabled 'portfast
trunk' on the port which reduced the port uptime significantly.
* Disabling a lot of negotiation protocols improves port initialization
time as well

However we still lose about 5 pings. Digging further, I find that it takes
about 4 seconds for the 6500 to register a port-transition. Down to up or
up to down. So from the moment, a cable is plugged in, it takes about 4
seconds for the SP to register the port as up and pass traffic. This is
just layer 1, not spanning-tree or anything.

Is this as good as it gets or is there a trick to perhaps get this time
further down?


On Sat, Jul 13, 2013 at 9:19 AM, james <james at mutexit.com> wrote:

> He is utilizing bpduguard as well so that should help reduce the chance of
> a loop.
>
>
> Sent from my Verizon Wireless 4G LTE Smartphone
>
>
>
> -------- Original message --------
> From: Tóth András <diosbejgli at gmail.com>
> Date: 07/12/2013 6:00 PM (GMT-05:00)
> To: Tom Storey <tom at snnap.net>
> Cc: Shanawaz Batcha <ismath.shaan at gmail.com>,cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Cisco trunk port startup delay
>
>
> 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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