[c-nsp] Lot of input errors on a NPE-G1 interface

[Chuck Church]

Regarding that IPTV issue, there is a Cisco switch option to not flush IGMP
table mappings when a TCN goes out, that accomplishes the same thing as
portfast, but without the (slight) risk of using that:

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/31sga/configu
ration/guide/multi.html#wp1049520

Chuck

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Thursday, May 24, 2012 5:38 AM
To: adam vitkovsky
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Lot of input errors on a NPE-G1 interface

Hi,

On Thu, May 24, 2012 at 12:38:49PM +0200, adam vitkovsky wrote:
> What do you think about enabling port-fast on trunks between switches 
> that are connected in a star topology (no redundant links) and running 
> MST

I do not run MST anywhere, so I'm not sure how portfast and MST interact.

OTOH, if you connect switches with *RSTP* together, the links will be up and
forwarding in very short time anyway, so portfast won't make much
difference.

> I'm asking because we have problems with TCN and following CAM table 
> flushes when ports flap We suspect that the CAM table flushes have 
> negative effects on IPTV streams There was the idea of enabling 
> port-fast on trunks since the topology is a cascaded star and when a 
> segment goes offline there's no other way to get to it -so no need for 
> the whole instance/domain to suffer from topology change And in case 
> the someone creates an artificial loop MST should take care of it as 
> soon as it hears the first bpdu right

Well, if you are *sure* your topology has no loops, then just turn off
spanning tree.  No TCNs.

gert
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Gert Doering - Munich, Germany
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fax: +49-89-35655025
gert at net.informatik.tu-muenchen.de
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