From: Erick Bergquist (ebergquist@ameritech.net)
Date: Tue Jun 28 2005 - 01:56:15 GMT-3
From my experience/knowledge of this topic, the voice
vlan command populates the CDP packet voice vlan field
with the vlan # of the voice vlan # so the phone knows
what vlan to put voice traffic on. Since cisco ip
phones listen to CDP to get this. Thats why other
vendors IP phones you need to manually set the voice
vlan on the phone.
With the access port method (pseudo-trunk is term I
like) less traffic is sent to phone then a
full-fledged port configured in trunk mode. Some of
the lower end model phones (7905, 7912, etc) can be
sensitive to amount of traffic/broadcasts/etc and to
much of that can cause those to reset depending on
firmware versions, etc or have voice quality issues.
Using the access-port method with those has cleaned up
phone reboots for us on chatty networks.
--- Ed Lui <edwlui@gmail.com> wrote:
> Gladston,
This archive was generated by hypermail 2.1.4
: Wed Jul 06 2005 - 14:43:44 GMT-3
>
> No doubt. There is NO ONE document can prove if it
> is correct or not. As I
> mentioned in previous post. Access port carries
> traffic for more than 1 vlan
> is not what most people learned. But this is what I
> found from cisco
> documentation and not just one. I checked both 3550
> and 6500(voice vlan=aux
> vlan) configuration from cisco.com
> <http://cisco.com>. Plus I(myself)
> actually labbed it up with 3550EMI+7960phone. Well,
> did I overlook
> something? It is possible. I am not a Network
> Engineer but really want to
> figure out the technology. So far, I know both trunk
> port and access port
> work as well.
>
> Actually, I keep thinking about the pros and cons
> for both. What is the
> advantage, overhead...etc. Like Brian Dennis said in
> one of the online
> seminars. I truly agree, understand the technology
> is the key point. Passing
> the lab is important. I don't feel good to myself if
> I get a chance to hold
> a number but don't know what myself is doing. Wish
> Chris Lewis can find out
> for us.
>
> :)
> Ed Lui
> P.S. Technology is changing every day. The standard
> is based upon the
> creator. Who knows if one day access port can carry
> no more than 5 vlans. It
> is all up to the creator.
>
>
>
> On 6/27/05, gladston@br.ibm.com
> <gladston@br.ibm.com> wrote:
> >
> >
> > Thanks for this invaluable feedback.
> >
> > Looking at Maurilio's book, page 96, as Chris
> pointed:
> >
> > Would you agree with the author statement
> "Ensure...that the native vlan
> > is 2".
> > As I see it, it is not necessary to configure
> native vlan (to have vlan 2
> > for data and vlan 50 for voice). One could let the
> native vlan as default,
> > configure the voice vlan to 50 and the data vlan
> to 2.
> >
> > Do you see any reason to configure native vlan to
> the same vlan as the
> > data vlan? (my point is that as 7960 talks dot1q,
> it can tag data vlan to
> > any value)
> >
> > Have you seen voice vlan configured on a access
> port? (I am asking this
> > because on the last time I posted this subject -
> sorry to post it again, but
> > it was not clear - a guy said it was possible). I
> argued: "How would the
> > voice vlan be transported if there is no dot1Q?"
> (similar as Chris
> > explained) and the guy answered that it was an
> exception.
> > It is hard to understand when the hardware is not
> available to test :)
> >
> >
> > Cordially
> >
>
------------------------------------------------------------------
> > Gladston
> >
> >
> >
> > *"Chris Lewis \(chrlewis\)" <chrlewis@cisco.com>*
> >
> > 25/06/2005 12:31
> > To
> > "Ed Lui" <edwlui@gmail.com> cc
> > "John Matus" <jmatus@pacbell.net>, Alaerte
> Gladston
> > Vidali/Brazil/IBM@IBMBR, <ccielab@groupstudy.com>
> Subject
> > RE: Voice VLAN - Access ports
> >
> >
> >
> >
> >
> >
> >
> > Hi Ed,
> >
> > Thanks for the reply, this has been a valuable
> exchange for me, as it has
> > made me rethink some things. However, please
> consider that Cisco
> > documentation on the web is imperfect, sometimes
> it is accurate from one
> > point of view, but can easily lead to incorrect
> conclusions, and sometimes
> > it is flat out wrong and won't work (my favorite
> current example is the
> > configuration for Outbound Route Filtering, it is
> missing the reference to
> > the prefix list, without which it does not work).
> Cisco documentation on the
> > web is a tremendous resource, but it should only
> be taken as a guide for
> > what the starting point for configuration in a lab
> should be IMHO.
> >
> > The best configuration example I have seen of
> voice vlan comes from
> > Maurilio Gorito's routing and switching practice
> lab book by Cisco press. In
> > practice lab 2, configurations are shown for
> connecting a 7960 that does
> > trunking, and a 7905 that does not do trunking.
> >
> > The port connecting to a 7960 is configured for
> trunking, and the port
> > connected to the 7905 is not. This is given on p96
> >
> > 3550 config for 7960 phone
> > int fa0/16
> > switchport access vlan 2
> > switchport trunk encapsulation dot1q
> > switchport trunk native vlan 2
> > switchport mode trunk
> > switchport voice vlan 50
> > no ip address
> > duplex full
> > speed 100
> > spanning-tree portfast
> >
> > 3550 config for 7905 phone
> > int fa0/17
> > switchport access vlan 50
> > no ip address
> > duplex half
> > speed 10
> >
> > The explanation is given as follows:
> >
> > The 7960 has the capability to trunk to the 3550
> as it has an on-board 3
> > port switch and can separate the voice and data
> traffic
> appropriately.The7905 phone only has 10 base T and
> needs manual insertion in
> to the voice
> > vlan. Ensure that the port connecting to the 7960
> is configured as a trunk
> > using dot1q and that the native vlan is 2.
> >
> > If you also look at the Cisco Press book Cisco
> Catalyst QoS, by Flanagan
> > et al, on page 63 you see the following:
> >
> > "Through the use of dot1q trunks, voice traffic
> from an IP phone connected
> > to an access port can reside on a separate VLAN
> and subnet. The workstation
> > attached to the Ip phone might still reside on the
> access, or native
> > VLAN........Subsequently, with the use of voice
> VLANs, all traffic is tagged
> > to and from the Cisco IP phone and Catalyst
> switch."
> >
> > Now one could argue that things like portfast are
> not needed for a trunk
> > mode in this configuration, and I would agree, but
> that is what Maurilio
> > gave in his book, and likely what they would be
> looking for on the lab exam,
> > which is the purpose of this list :)
> >
> > I think there are at least two sources of
> confusion in this documentation.
> > First is that not all IP phones are created equal,
> some do trunking and some
> > don't. The other is a potential dual use of the
> phrase access port. In some
> > contexts it can mean a non trunnking port, in
> others it can mean an ethernet
> > port (which can be configured for trunking or
> non-trunking).
> >
> > Cheers
> >
> > Chris
> > ------------------------------
> >
> >
> > *From:* Ed Lui [mailto:edwlui@gmail.com]
> > *Sent:* Saturday, June 25, 2005 12:27 AM
> > *To:* Chris Lewis (chrlewis)
> > *Cc:* John Matus; gladston@br.ibm.com;
> ccielab@groupstudy.com
> > *Subject:* Re: Voice VLAN - Access ports
> >
> > Chris,
> >
> > I have been struggling about 2 vlans on an access
> port for a while. I know
> > it works with either access port or trunk port let
> say with a 7960. What I
> > understand is, an access port can not carry
> traffic for more than 1 vlan.
> > Somehow, the documentation told me voice vlan is
> an exception. Then I labbed
> > it up myself(3550 EMI + 7960). The result is an
> access port can carry data
> > on one vlan and voice on another within the same
> access port. And that is
> > what the documentation said, too.
> >
> > Consider those underlined below. Portfast is for
> access port and not for
> > trunk port.
> >
> >
> > *Voice VLAN Configuration Guidelines*
> >
> > These are the voice VLAN configuration guidelines:
> >
> > - *You should configure voice VLAN on switch
> access ports.*
> > - Before you enable voice VLAN, we recommend
> that you enable QoS on
> > the switch by entering the mls qosglobal
> configuration command and
> configure
> > the port trust state to trust by entering the
> mls qos trustcosinterface
> > configuration command.
> > - *The Port Fast feature is automatically
> enabled when voice VLAN is
> > configured*. When you disable voice VLAN, the
> Port Fast feature is
> > not automatically disabled.
> >
> >
> > Per your config :
> > Int fa0/16
> > Switch access vlan 2
> > Switch trunk encap dot1q<---to be removed----->
> > Switch trunk native vlan 2<---to be removed----->
> > Switch mode trunk<---to be removed----->
> > Switch voice vlan 50
> > switchport priority extend cos 0
> > mls qos trust cos < or "mls qos trust device
> cisco-phone" should also work
> > >
> >
> > It works with those lines removed. But also WORKS
> WITH THOSE LINES. I am
> > so confuse about the configurations. Wish someone
> can explain the Pros and
> > Cons between the 2. Finally, I also have the same
> book you guys have and
> > understand it says trunk port configuration needs
> to be included. On the
> > other hand, documentation from *cisco.com*
> <http://cisco.com> said access
> > port.
> >
> > :)
> > Ed Lui
> >
> >
> >
> >
> >
> >
> > On 6/24/05, *Chris Lewis (chrlewis)*
> <*chrlewis@cisco.com*<chrlewis@cisco.com>>
> > wrote:Hi,
> >
> > John, that is correct, the 7960 uses trunking, the
> cheaper ones do not.
> >
> > Ed, my question to you is if you are told to
> configure a switch port to
> > have voice traffic from the phone in vlan 50 and
> data traffic from a PC
> > attached to the phone in vlan 2, how can you do
> that without configuring
> > trunking on the port? Clearly you would not want
> data traffic rom the PC
> > in the same vlan as the voice traffic, otherwise
> it ceases to be a voice
> > vlan :)
> >
> > Chris
> >
> > -----Original Message-----
> > From: John Matus [mailto:*jmatus@pacbell.net*
> <jmatus@pacbell.net> ]
> > Sent: Friday, June 24, 2005 9:32 PM
> > To: Ed Lui; Chris Lewis (chrlewis)
> > Cc: *gladston@br.ibm.com* <gladston@br.ibm.com>;
> *ccielab@groupstudy.com*<ccielab@groupstudy.com>
> > Subject: Re: Voice VLAN - Access ports
> >
> > my ciscopress lab book is in the
> car...........but....
> > i think it all depends on which type of phone you
> are using.
> >
> > i believe that the cheapy phones actually use the
> "switch access vlan"
> > for their traffic and a more expensive one <if i
> can remember correctly,
> > the 7960 phone??> uses trunking.
> >
> >
> > Regards,
> >
> > John D. Matus
> > MCSE, CCNP
> > Office: 818-782-2061
> > Cell: 818-430-8372
> > *jmatus@pacbell.net* <jmatus@pacbell.net>
> > ----- Original Message -----
> > From: "Ed Lui" <*edwlui@gmail.com*
> <edwlui@gmail.com>>
> > To: "Chris Lewis (chrlewis)" <*chrlewis@cisco.com*
> <chrlewis@cisco.com>>
> > Cc: <* gladston@br.ibm.com*
> <gladston@br.ibm.com>>; <*
> > ccielab@groupstudy.com* <ccielab@groupstudy.com>>
> > Sent: Friday, June 24, 2005 6:34 PM
> > Subject: Re: Voice VLAN - Access ports
> >
> >
> > > Chris,
> > > It doesn't sound like what I learned from the
> DocCD. According to the
> > > DocCD. Switch port connected to IPphone should
> be configured as access
> >
> > > port
> > > and NOT TRUNK. Take a look :
> > > Voice VLAN Configuration Guidelines
> > >
> > > These are the voice VLAN configuration
> guidelines:
> > >
> > > - You should configure voice VLAN on switch
> access ports.
> > > - Before you enable voice VLAN, we recommend
> that you enable QoS on
> > > the switch by entering the mls qos global
> configuration command and
> > > configure the port trust state to trust by
> entering the mls qos
> > trust
> > > cos interface configuration command.
> > > - The Port Fast feature is automatically enabled
> when voice VLAN is
> > > configured. When you disable voice VLAN, the
> Port Fast feature is
> > not
> > > automatically disabled.
> > > - When you enable port security on an interface
> that is also
> > > configured with a voice VLAN, you must set the
> maximum allowed
> > secure
> > > addresses on the port to at least two.
> > > - If any type of port security is enabled on the
> access VLAN,
> > dynamic
> > > port security is automatically enabled on the
> voice VLAN.
> > > - You cannot configure static secure or sticky
> secure MAC addresses
> > on
> > > a voice VLAN.
> > > - Voice VLAN ports can also be these port types:
> > > - Dynamic access port. See the "Configuring
> Dynamic Access Ports
> > > on VMPS Clients"
> > >
> > section<
>
*http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e
> > *
>
<http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e>
> > a1/35
> > > 50scg/swvlan.htm#94106>for
> > > more information.
> > > - Secure port. See the "Configuring Port
> Security"
> > >
> >
>
section<*http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e*
>
tp://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e>
> > a1/35
> > > 50scg/swtrafc.htm#86378>for
> > > more information.
> > > - 802.1X authenticated port. See the "Using
> 802.1X with Voice
> > > VLAN Ports"
> > >
> >
>
section<*http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e
> > *
>
<http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e>
> > a1/35
> > > 50scg/sw8021x.htm#50544>for
> > > more information.
> > > - Protected port. See the "Configuring Protected
> Ports"
> > >
> > section<*
>
http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e
> > *
>
<http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114e>
> > a1/35
> > > 50scg/swtrafc.htm#56161>for
> > > more information
> > >
> > > HTH,
> > > Ed Lui
> > >
> > > On 6/24/05, Chris Lewis (chrlewis) <
> *chrlewis@cisco.com*<chrlewis@cisco.com>>
> > wrote:
> > >>
> > >> This is a config that I believe works to make
> vlan 50 the voice vlan,
> > >> and vlan 2 to be the data vlan, then sets data
> from the PC to CoS 0
> > and
> > >> trusts CoS from the phone.
> > >>
> > >> Mls qos
> > >>
> > >> Vlan 50
> > >> Name voice vlan
> > >>
> > >> Int fa0/16
> > >> Switch access vlan 2
> > >> Switch trunk encap dot1q
> > >> Switch trunk native vlan 2
> > >> Switch mode trunk
> > >> Switch voice vlan 50
> > >> switchport priority extend cos 0
> > >> mls qos trust cos
> > >>
> > >> The switch access configuration in the
> interface defines what vlan
> > the
> > >> port belongs to if for some reason the port
> stops trunking. Voice
> > vlan
> > >> has to work on a trunk port for there to be
> traffic that are members
> > of
> > >> two vlans on it.
> > >>
> > >> It could be possible that the documentation you
> refer to is listing a
> > >> restriction for configuring port security in
> addition to voice vlan,
> > >> although I don't know for sure.
> > >>
> > >> Chris
> > >>
> > >> -----Original Message-----
> > >> From: *nobody@groupstudy.com*
> <nobody@groupstudy.com> [mailto:*
> > nobody@groupstudy.com* <nobody@groupstudy.com> ]
> On Behalf
> > Of
> > >> *gladston@br.ibm.com* <gladston@br.ibm.com>
> > >> Sent: Wednesday, June 22, 2005 12:14 PM
> > >> To: *ccielab@groupstudy.com *
> <ccielab@groupstudy.com>
> > >> Subject: Voice VLAN - Access ports
> > >>
> > >> Hi,
> > >>
> > >> Looking for Port security information I read
> this:
> > >>
> > >> "Voice VLAN is only supported on access ports
> and not on trunk ports,
> > >> even though the configuration is allowed"
> > >>
> > >>
> >
>
*http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225seb/scg/s
> >
>
*<http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225seb/scg/s>
> > >> wtrafc.htm#wp1038501
> > >>
> > >> Some time ago I was researching about this
> subject (if it would be
> > >> allowed to configure an interface connected to
> an IPPhone with
> > >> 'switchport mode trunk').
> > >> One of the answers was 'yes'.
> > >>
> > >> Do you know if an IPPhone only works if the
> port is configured as
> > access
> > >> port?
> > >> If yes, how does it work, considering the
> previous Cisco statement?
> > >>
> > >> Thanks for any feedback.
> > >>
> > >>
> >
>