From: Marcus Jensen (marcus@pobox.com)
Date: Sun Aug 03 2003 - 03:38:17 GMT-3
Glen, I agree with you on those two commands and your comments. The priority
extend command to help the phone keep its priority above whatever the PC is
sending. I read on CCO two slightly conflicting descriptions though. One was
need to set priority extend to zero to have any overriding functionality at
all. This doesn't quite make sense and it was an earlier version of code DOC
I think, but zero sounds advisable anyway for most situations. The latest
12.1.14 version of 3550 seems to have additional/clearer QoS descriptions
than prior versions.
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114ea1/3550scg/s
wqos.htm
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Glenn Johnson
Sent: Sunday, August 03, 2003 2:22 PM
To: ccielab@groupstudy.com
Subject: voice vlan/cos
If you use this on any given 3550 switchport:
1) mls qos cos 5
mls qos cos override
[ Presumably overrides whatever is
coming into the switch port (voice and data)
from the phone/pc and sets COS to 5 ]
and then enter this:
2) switchport priority extend cos 5
[ Presumably instructs the IP phone(?) to
override whatever cos might be coming from
an attached PC and sets COS to 5 ]
Is command 2 superfluous?
Could voice traffic theoretically suffer, relative to data, on the way to
the 3550 switch port if an attached PC had all data traffic set at COS 7 and
command 2 was not used. I guess it comes down to what level of COS
processing/prioritization, if any, can be done by the IP phone with its
integrated switch before info is forwarded on to the 3550 switch. Thanks in
advance for any comments. I have seen
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12113ea1/3550scg/s
wvoip.htm
and
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12113ea1/3550scg/s
wqos.htm
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