From: McClure, Allen (Allen.McClure@Yum.com)
Date: Wed Sep 17 2003 - 11:05:58 GMT-3
Really appreciate it folks. I think everyone sees my point on why this
little feature is frustrating.
Here's a document I found a while back and use as my "official" answer
until I find something more authoratative.
http://www.cisco.com/en/US/customer/tech/tk648/tk361/technologies_tech_n
ote09186a0080114aee.shtml
Allen G. McClure
CCNP/CCDP/MCSE
Yum! Brands, Inc.
Sr. Network Analyst
allen.mcclure@yum.com
-----Original Message-----
From: Scott Morris [mailto:swm@emanon.com]
Sent: Tuesday, September 16, 2003 6:00 PM
To: 'Shawn Yang'; McClure, Allen; ccielab@groupstudy.com
Subject: RE: Cat3550 voice vlan
While the 3550 may be twisted, that's not the answer. The CatOS
switches work the same way with vlan's and auxilliary vlan's on the
ports.
From a coding standpoint, the separation is quite simple. You are
either receiving a packet tagged or untagged. You put the tagged things
in one vlan and the untagged things in another. You don't need to have
a full trunking conversation to figure that one out!
By configuring a trunk, you are telling your switch that ALL vlan
traffic "could be" capable of going down that line. Are you limiting
then which vlans the trunk is configured for? Hope so. Seems like a
waste of statements to configure in the end though when all you're doing
with your switchport trunk commands is what the access vlan and voice
vlan commands do already! :)
Call me silly, but I'm all for simple!
But both will indeed work from a purely techincal point of view.
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Shawn Yang
Sent: Tuesday, September 16, 2003 6:42 PM
To: McClure, Allen; Shawn Yang; ccielab@groupstudy.com; McClure, Allen
Subject: RE: Cat3550 voice vlan
OK. I have read through the previous discussion threads on this
topic,
here let me gather what i have understood.
Basically the port can work under both configs, i.e, trunk port
config
(my way) and access port config (IPE solution). The trunk port
config
is more obvious and intuitive. But how does the second config also
work?
Should an access port discard all tagged packets?
The answer might be that cat3550 is a "twisted" beast, different
from both a traditional switch and a traditional router. In fact,
its software is a blend of IOS and CatOS. And its many features
are halfway between a router and a switch, like Port ACLs, and
Vlan
ACLs, etc.
For voice, when an access port is configured with a voice vlan, it
starts to recognize/accept dot1Q encapped packets, (only for the
voice
vlan, however.) So it is in fact half way between an access port,
and a trunk port. Think of such ports as access ports with limited
trunking capability ----- again, a twisted feature.
And of course, when regarded as a trunk, the port's access vlan
automatically
becomes the native vlan...
Cisco seems to prefer the second config, because it is obviously
much
simpler and more scalable. In Cat3550 config guide they explicitly tell
you to config voice vlan on access ports.
http://127.0.0.1:8080/cc/td/doc/product/lan/c3550/12112cea/3550scg/
swvoip.htm#85659
How does this sound?
Shawn
---------- Original Message ----------------------------------
From: "McClure, Allen" <Allen.McClure@yum.com>
Reply-To: "McClure, Allen" <Allen.McClure@yum.com>
Date: Tue, 16 Sep 2003 17:00:16 -0500
>Perhaps I shouldn't have assumed a PC. With a phone only it uses
CDP to
>figure it out on an access port, correct?
>
>A repost or link to an authoritative explanation would be helpful
for me
>as well. I've been following the list for a long time and never
felt
>like anyone nailed it. I could've easily missed it however.
>
>Allen G. McClure
>CCNP/CCDP/MCSE
>Yum! Brands, Inc.
>Sr. Network Analyst
>allen.mcclure@yum.com
>
>
>
>
>
>-----Original Message-----
>From: McClure, Allen
>Sent: Tuesday, September 16, 2003 4:53 PM
>To: 'Shawn Yang'; ccielab@groupstudy.com
>Subject: RE: Cat3550 voice vlan
>
>
>They're wrong.
>
>I would add native vlan configuration for untagged data (PC)
packets (a
>reasonable assumption), although the requirement doesn't specify
a PC
>connected to the phone.
>
>I'd love to hear more comments on this... I've been wrestling
with the
>"right" way to answer this question for quite some time.
>
>Allen G. McClure
>CCNP/CCDP/MCSE
>Yum! Brands, Inc.
>Sr. Network Analyst
>allen.mcclure@yum.com
>
>
>
>-----Original Message-----
>From: Shawn Yang [mailto:syang@bitfone.com]
>Sent: Tuesday, September 16, 2003 1:22 PM
>To: ccielab@groupstudy.com
>Subject: Cat3550 voice vlan
>
>
>Hi, people,
>
>Here is one question in Ipexpert 4.0, appendix H.
>
>(For Cat3550)
>There is a Cisco 7960 IP phone connected to fa 0/15, configure
the port
>as if the phone will be forwarding its voice traffic with 802.1q
>information. Voice vlan is 100.
>
>My answer:
>
>mls qos
>
>int fa 0/15
> swi trunk encap dot1q
> swi mode trunk
> swi voice vlan 100.
> mls qos trust cos
>
>The solution:
>
>int fa 0/15
> swi mode access
> swi voice vlan 100
>
>I am having problem accepting this solution. Should a voice port
have to
>be a trunk port? Because it has to carry at least two vlans,
voice, and
>data? also "mls qos" is not enabled...
>
>Anyone can help me?
>
>Shawn
>
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