From: Charles Church (cchurch@wamnet.com)
Date: Fri Sep 05 2003 - 23:12:10 GMT-3
dt,
Native vlan is an interface by interface setting. No reason you can't have
VLAN 10 native on one port, and VLAN 20 native on the other. So if you've
got a configuration like this:
ciscophone-VoiceVLAN10-3550-trunk native 10-3550-trunk native
1-3550-non-cisco phone vlan 10
Your traffic from the phone to the non-cisco phone will get a dot1q header
as it leaves your phone, the 3550 it hits first will strip of the dot1q
header, and forward it over the trunk to the next 3550. Since that trunk is
native on VLAN 10, there's no header. The second 3550 receives it, and
bridges it towards the 3rd 3550, with a dot1q header since that trunk is
native on VLAN 1. Finally, the 3rd 3550 gets it, and sends it to the
non-cisco phone. Since it's non-cisco, it had a trunk manually configured.
It'll get a get a dot1q header on the last link to the non-cisco phone.
Hope that clears it up a bit.
Chuck Church
CCIE #8776, MCNE, MCSE
Wam!Net Government Services
13665 Dulles Technology Dr. Ste 250
Herndon, VA 20171
Office: 703-480-2569
Cell: 703-819-3495
cchurch@wamnet.com
PGP key: http://pgp.mit.edu:11371/pks/lookup?search=chuck+church&op=index
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
ccie2be
Sent: Friday, September 05, 2003 11:34 AM
To: Group Study; navaid@rogers.com
Subject: Re: 3550 and IP Phone Verification
Hi Navaid,
Thanks for getting back to me.
How can that be? Are you saying a Cat 3550 can have more than one native
vlan? And, that different ports on the same Cat 3550 can be in different
native vlans?
Won't broadcast frames from a native vlan be switched to all ports
configured in a native vlan which condradicts the whole concept of a vlan as
a broadcast domain?
dt
----- Original Message -----
From: <navaid@rogers.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; "Group Study" <ccielab@groupstudy.com>
Sent: Friday, September 05, 2003 10:14 AM
Subject: Re: 3550 and IP Phone Verification
> Keep native vlan 1 for your trunk.
> Make vlan 10,20,30,40 native for access ports based on your requirements.
>
> Navaid
> >
> > From: "ccie2be" <ccie2be@nyc.rr.com>
> > Date: 2003/09/05 Fri AM 10:00:31 EDT
> > To: "Group Study" <ccielab@groupstudy.com>
> > Subject: 3550 and IP Phone Verification
> >
> > Hi everyone,
> >
> > I want to confirm my understanding of the situation where IP Phones are
> > connected to a 3550.
> >
> > Let's say that a firm has just upgraded their switches to Cat 3550's in
> > preparation of a migration to IP Telephony. With the upgrade they have
the
> > same number of ethernet ports that they had with the old switches and
their
> > intention is to have all the PC's that were previously connected to the
old
> > switches connect via the access port on the IP Phone which in turn will
be
> > connected to the new Cat 3550 switches. Currently, their PC's reside in
4
> > different vlans, vlan 10, 20, 30 and 40 and all of these vlans exist in
each
> > of their switches. Their plan is to have all the IP Phones in one voice
vlan.
> > And, they need the PC's to remain in whatever vlan they're already in
after
> > the migration.
> >
> > Can this be achieved?
> >
> > Based on what I understand, this can't be done. Here's the reason.
Please
> > correct me if I'm wrong on this.
> >
> > Data traffic from the PC's attached to the access port of the IP Phones
is
> > carried in untagged frames in the native vlan. While the native vlan
can be
> > assigned any vlan number there can be only 1 native vlan which, by
default, is
> > vlan 1. And, the native vlan must be the same on all the Cat 3550's
since
> > 802.1q trunks area being used.
> >
> > While this is my understanding from reading the 3550 config guide, this
> > limitation doesn't seem reasonable or smart. Would Cisco design the
3550 so
> > that PC's that were in different vlans would be forced to be in the same
vlan
> > if the PC's were connected via the IP Phone?
> >
> > Thanks; I greatly appreciate any help.
> >
> > dt
> >
> >
> > _______________________________________________________________________
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>
> 1
>
>
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