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Re: 3550 and IP Phone Verification posted 09/05/2003
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If theIP Phones are Cisco then:
switchport access vlan 10
switchport voice vlan 99 (just an example)

If non-Cisco IP Phone:
switchport trunk native 10 (for PC vlan)
switchport trunk encapsulation dot1q


----- Original Message -----
From: "ccie2be" <ccie2be@xxxxxxxxxx>
To: "Group Study" <ccielab@xxxxxxxxxxxxxx>
Sent: Friday, September 05, 2003 7:00 AM
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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