[c-nsp] Performance Degradation Using VLANs

[Church, Chuck]

I went through this problem also.  I think the exact case (at least on
the 2600s) was that CEF was supported on ISL trunks, but not dot1q until
the versions that Pete mentioned below.  This was summer of 2002 when I
dealt with it, which was just before 12.2 was GD, so the versions sound
about right.


Chuck Church
Lead Design Engineer
CCIE #8776, MCNE, MCSE
Netco Government Services - Design & Implementation Team
1210 N. Parker Rd.
Greenville, SC 29609
Home office: 864-335-9473
Cell: 703-819-3495
cchurch at netcogov.com
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x4371A48D 


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Pete Templin
Sent: Wednesday, November 17, 2004 7:57 PM
To: Rodney Dunn
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Performance Degradation Using VLANs

Rodney Dunn wrote:
> The performance hit would be very very little.
> 
> That's because the mac header rewrite is prebuilt
> by CEF to include the vlan/dmac/smac information
> and it's preprened just like if the vlan isn't
> there.
> 
> You would have to test it to get exact numbers but
> I've never seen anyone mention a difference in
> the software forwarding path when adding subinterfaces
> as a trunk that map to vlans.

Just for the sake of mentioning, this would be for 12.1(3)T (and later),

12.2, 12.2T, 12.3, and 12.3T release trains.  I learned the hard way 
that subinterfaces in 12.0 do not seem to have full CEF support.

pt
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