From: Copleston, Daniel (LDN Int) (dcopleston@manfinancial.com)
Date: Tue Nov 02 2004 - 14:01:10 GMT-3
This will also work with non-Cisco phones that do not support CDP as long as
the phone supports some other method of finding out that it should tag its
packets. We find config such as the below on a 3750 works fine with Nortel
handsets that use additional DHCP options to find out that they should tag
packets:
interface FastEthernet4/0/12
switchport access vlan 5
switchport mode access
switchport voice vlan 498
spanning-tree portfast
!
In this set-up the phone initially aquires a DHCP provided IP address on the
access vlan but the DHCP details also tell the phone the vlan it should be
on. At this point the handset releases the IP address it had obtains and
sends a 2nd DHCP request but this time with the Ethernet frames tagged with
the VLAN ID specified in the first DHCP response - the result is an IP
address in the voice VLAN is assigned and the phone tags all Ethernet frames
orginated. The switch accepts these frames and treats them correctly without
any additional trunking configuration.
Thanks
Dan
-----Original Message-----
From: David Pues (dpues) [mailto:dpues@cisco.com]
Sent: 02 November 2004 16:48
To: Brian McGahan; reo@chavallos.net; ccielab@groupstudy.com
Subject: RE: voice Vlan
It all depends on the type of switch used. Basically a trunk is NOT a
requirement between the IP phone and the switch except eg for a switch
module in a router.
The voice vlan config is basically there to let the phone know via CDP
how to tag the packets it sends (originated from the phone). At that
moment the phone will just pick this up via CDP and when ever it sends a
packet, it will tag it. The way Cisco has implemented this does not
require a trunk to be there (with the above exception). In this mode,
the switch will also not tag any packets out the port, which is not
required as the phone just looks at the destination MAC address and only
sends these packets to its logic (phone does MAC filtering). It does not
really look at the tags.
The voice vlan has a significance upstream to the network, not
downstream to the phone/pc.
Eg on a Cat4k, cat6k, cat3550 etc, putting the port in access mode into
the data vlan and assigning the voice/auxiliary vlan should do the
trick.
When you do configure a .1Q trunk, make sure to configure the data vlan
for the pc as the native vlan (as the phone just forwards the packets
which are not destined for the phone logic, without untagging the
packet) unless the daisy-chained device understands the tags....
So, Ahmed, native vlans are used when trunking and makes sure that the
data packets are untagged; access vlan is used in access mode.
My 2 cents,
David - CCIE 9666
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Brian McGahan
Sent: Tuesday, November 02, 2004 5:29 PM
To: reo@chavallos.net; ccielab@groupstudy.com
Subject: RE: voice Vlan
You cannot issue the "switchport mode access" command on the
interface otherwise trunking negotiation cannot occur.
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987 x 705
Outside US: 775-826-4344 x 705
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> reo@chavallos.net
> Sent: Tuesday, November 02, 2004 9:51 AM
> To: ccielab@groupstudy.com
> Subject: Re: voice Vlan
>
> Here's an example
>
> ---
> interface GigabitEthernet1/2
> no ip address
> switchport
> switchport access vlan 30
> switchport mode access
> switchport voice vlan 130
> ---
>
> ----- Original Message -----
> From: "Ahmed Hassan" <ahmed_hassan@rayatelecom.net>
> To: <ccielab@groupstudy.com>
> Sent: Tuesday, November 02, 2004 1:01 AM
> Subject: voice Vlan
>
>
> > HI,
> > When we configure a port with the command Switchport voice Vlan 20
> >
> > How we configure the data VLAN on the same port
> >
> > Switchport access vlan 10
> >
> > Or
> >
> > Switchport native vlan 10
> >
> > Or Both
> > Switchport access vlan 10
> > Switchport native vlan 10
> >
> > Best Regards
> > Ahmed Hassan
> > Product Development Supervisor
> > Raya Telecom
> >
> >
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