From: Farrukh Haroon (farrukhharoon@gmail.com)
Date: Wed Dec 03 2008 - 09:48:07 ARST
Couldn't agree more on this (with Scott).......However I wish I had studied
journalism to phrase it like Scott hehehe :)
Regards
Farrukh
On Wed, Dec 3, 2008 at 2:39 PM, Scott Morris <smorris@internetworkexpert.com
> wrote:
> That's a fancy name for a small trunk. I agree. If you have tagged
> frames,
> it's a trunk.
>
> If it has two wheels and pedals, it's a bicycle. They have some weird
> looking ones these days, but they're still bicycles.
> Call it a multi-unicycled transportation device if you want, but it's still
> a bicycle.
>
> Would you see anything different if you turned off CDP, set the port as a
> trunk port, used the trunk allowed vlan command to only allow the
> access/voice vlans, set the native vlan to equal the data vlan and went
> down
> that path?
>
>
> Scott Morris, CCIE4 #4713, JNCIE-M #153, JNCIS-ER, CISSP, et al.
> CCSI/JNCI-M/JNCI-ER
> Senior CCIE Instructor
>
> smorris@internetworkexpert.com
>
>
>
> Knowledge is power.
> Power corrupts.
> Study hard and be Eeeeviiiil......
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Asawilunda
> Sent: Wednesday, December 03, 2008 5:47 AM
> To: Carlos G Mendioroz
> Cc: ccielab@groupstudy.com
> Subject: Re: Voice vlan
>
> Cisco calls this a Multi-Vlan access port, and NOT a trunk port. if it were
> a trunk port, according to Cisco, it would flood all vlans configured on
> the
> switch out to the phone. As you probably know already, a port configured
> for
> voice Vlan does not flood out all Vlans to the phone, just the voice vlan
> frames (tagged) and the data frames ( untagged ). Below is a copy and paste
> from Cisco - ARCHv2-
>
>
> Multiservice switches supports a new parameter for IP Telephony support
> that
> makes the access port a multi-VLAN access port. The new parameter is called
> an auxiliary VLAN. Every Ethernet 10/100/1000 port in the switch is
> associated with two VLANs
>
> - A Native VLAN for data service that is identified by the port VLAN
> identifier or PVID
>
>
> - An Auxiliary VLAN for voice service that is identified by the voice
> VLAN identified or VVID.
> - During the initial CDP exchange with the access switch, the IP phone
> is configured with a VVID.
>
>
> - The IP phone also supplied with a QoS configuration using Cisco
> Discovery Protocol. Voice traffic is separated from data, and supports
> a
> different trust boundary.
>
> Data packets between the multiservice access switch and the PC or
> workstation will be on the native VLAN. All packets going out on the native
> VLAN of a 802.1q port are sent untagged by the access switch. The PC or
> workstation connected to the IP phone usually sends untagged packets.
>
> Voice packets will be tagged by the IP phone based on the Cisco Discovery
> Protocol information from the access switch.
>
> *The multi-VLAN access ports are not trunk ports, even though the hardware
> is set to dot1q trunk*. The hardware setting is used to carry more than two
> VLANs, but the port is still considered an access port that is able to
> carry
> one native VLAN and the Auxiliary VLAN. The *switchport host* command can
> be
> applied to a multi-VLAN access port on the access switch.
>
> On Wed, Dec 3, 2008 at 10:27 AM, Carlos G Mendioroz <tron@huapi.ba.ar
> >wrote:
>
> > Mark,
> > 802.1Q defines a frame format, which is capable of carrying both a QoS
> > mark (COS) and a VlanID.
> >
> > We kind of agreed in calling trunk a link which has a multivlan
> capability.
> > I'm basically saying that you can setup a port to honour the COS
> > marking w/o paying attention to VlanID.
> >
> > I got sidetracked by my sneefer port filtering vlan tags (Intel pro,
> > changed OS recently, had to reinstall driver, play with registry et
> > al.) I'll post my findings shortly.
> >
> > -Carlos
> >
> > Mark Stephanus Chandra @ 2/12/2008 21:34 -0200 dixit:
> >
> > HI Carlos,
> >>
> >> Your statement is still confusing, having 802.1p without a trunk, but
> >> it carried by dot1q. dot1q is a trunk right ?
> >>
> >> Someone in the group once said that even we configure the port
> >> switchport mode access, but when we add voice vlan configuration, the
> >> port change to a trunk actually.
> >> Is it true ?
> >>
> >> Any lab result ?
> >>
> >> Regards
> >>
> >> Mark Stephanus Chandra
> >> IT Consultant
> >>
> >> -----Original Message-----
> >> From: Carlos G Mendioroz [mailto:tron@huapi.ba.ar] Sent: 02 Desember
> >> 2008
> >> 18:01
> >> To: Radioactive Frog
> >> Cc: mark.chandra@gmail.com; ccielab@groupstudy.com
> >> Subject: Re: Voice vlan
> >>
> >> Hmm, let's clear it up (what you propose, I mean).
> >> First, what you configure at the switch is not always going to change
> >> the way the phone does things, and AFAIK, 802.1p as configured in the
> >> switch is going to affect the way the switch handles the rx packets,
> >> so no way to see if it works (wrt trunk/no trunk) by inspecting
> >> packets in the link.
> >>
> >> I don't know what you mean by "not working if you don't activate trunk".
> >> Now that we agree (I hope) that trunk := multi vlan, what I say is
> >> that you can have the phone use 802.1p (riding 802.1Q frames) to do
> >> QOS marking without having a trunk, i.e., having both data and voice
> >> traffic on same vlan (or not using the vlan id in the 802.1Q frame to
> >> actually switch the voice packet).
> >>
> >> I have not labbed this, but I do believe it works like that.
> >> If you think it does not, I'll go ahead and lab it up.
> >>
> >> -Carlos
> >>
> >>
> >> Radioactive Frog @ 2/12/2008 8:46 -0200 dixit:
> >>
> >>> Indeed, good discussion mate...
> >>> ok lets first define the trunk :)
> >>> trunk is to pass multple vlan and it increases the normal ethernet
> >>> frame size [8021q tag we call that].
> >>> without trunking you can't inject 802.1p in the ethernet frame.
> >>>
> >>> re;
> >>> *switchport voice vlan *{/vlan-id | /dot1p /| /none /| /untagged}
> >>>
> >>>
> >>>
> >> http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/re
> >> lease/1 2.2_25_sea/configuration/guide/swvoip.html
> >>
> >>> *here is what dot1p part of above command does; dot1p*-Configure the
> >>> Cisco IP Phone to use 802.1p priority tagging for voice traffic and
> >>> to use the default native VLAN (VLAN 0) to carry all traffic. By
> >>> default, the Cisco IP Phone forwards the voice traffic with an
> >>> 802.1p priority of 5
> >>>
> >>> I think that command should** only activate once you turn the
> >>> trunking on.
> >>> lab it up and see if packets are being tagged by just issueing that
> >>> one line (without switchport encapsulation dot1q).
> >>>
> >>> been there done that!!
> >>>
> >>> By default, the Cisco IP Phone forwards the voice traffic with an
> >>> 802.1Q priority of 5
> >>>
> >>> that is if you don't put anything after - switchport voice vlan 100
> >>>
> >> <dot1p>
> >>
> >>> When I was doing my masters degree, this used to be a big topics to
> >>> discuss and most people still confussed about it.
> >>>
> >>> Good one!!
> >>>
> >>>
> >>>
> >>> On Tue, Dec 2, 2008 at 9:26 PM, Carlos G Mendioroz
> <tron@huapi.ba.ar<mailto:
> >>> tron@huapi.ba.ar>> wrote:
> >>>
> >>> For the strong disagreement, I guess we have to polish what we mean
> >>> for "trunk".
> >>>
> >>> My view is a link carrying many vlans. A link with just one vlan,
> even
> >>> if using 802.1q/p is not really a trunk (again, my view).
> >>>
> >>> This is in line (if not forced by) the way you actually configure
> >>> cisco switches where you can enable 802.1p rx by doing
> >>> (config)# switchport voice vlan dot1p
> >>>
> >>> -Carlos
> >>>
> >>> Radioactive Frog @ 2/12/2008 8:04 -0200 dixit:
> >>>
> >>>
> >>>
> >>> On Tue, Dec 2, 2008 at 8:50 PM, Carlos G Mendioroz
> >>> <tron@huapi.ba.ar <mailto:tron@huapi.ba.ar>
> >>> <mailto:tron@huapi.ba.ar <mailto:tron@huapi.ba.ar>>> wrote:
> >>>
> >>> Well, not quite.
> >>> Even if *link* is access, phone can mark TOS.
> >>>
> >>>
> >>> Agreed....TOS = layer3
> >>>
> >>>
> >>> Even if *link* is access, phone can use 802.1p to mark COS
> >>>
> >>>
> >>> strongly disagreed as 802.1p can only go with Trunk when packet
> >>> length is scratched a bit using tagging.
> >>> in other word 802.1p is part of 802.1q or 1d frame format: (3bit
> >>> field of 802.1q header is used byu 802.1p).
> >>>
> >>> Check the 802.1q frame header. If you don't tag it won't can't
> >>> carry 1p bit.
> >>>
> >>> And even is *port* is admin access, it will turn stealthy to
> >>> trunk
> >>> when it discovers a (CDP enabled ?) phone is voice vlan is
> >>>
> >> there:
> >>
> >>> Switch#sh int f0/8 switchport
> >>> Name: Fa0/8
> >>> Switchport: Enabled
> >>> Administrative Mode: dynamic desirable
> >>> Operational Mode: static access
> >>> Administrative Trunking Encapsulation: dot1q
> >>> Operational Trunking Encapsulation: native
> >>> Negotiation of Trunking: On
> >>> Access Mode VLAN: 2 (Lab)
> >>> Trunking Native Mode VLAN: 1 (default)
> >>> Voice VLAN: 1 (default)
> >>> ...
> >>>
> >>> (in modern switches at least, it used not to be that way)
> >>> -Carlos
> >>>
> >>> Radioactive Frog @ 2/12/2008 5:41 -0200 dixit:
> >>>
> >>> The idea of voice vlan is phone generates ef or cs3
> >>> streams and
> >>> switch
> >>> prioritize that all the way tilll it see's
> server/endpoint.
> >>>
> >>> priority field only can be read if the packet is trunked
> >>> (injected extra
> >>> header in the frame),. If thats link from switch to
> >>> phone
> >>>
> >> is
> >>
> >>> not trunked
> >>> switch wont' know what kind of frame the phone is
> sending.
> >>>
> >>> so back to yoru first question, if you applying 'voice
> vlan
> >>> under interface'
> >>> then it has to be a trunk port.
> >>>
> >>> if port is access port then phone can't mark its frames
> >>> with any
> >>> cos/tos
> >>> bits.
> >>>
> >>> hth...
> >>>
> >>> -frog
> >>> CCIE#21569
> >>>
> >>> On Tue, Dec 2, 2008 at 5:59 PM, <mark.chandra@gmail.com
> >>> <mailto:mark.chandra@gmail.com>
> >>> <mailto:mark.chandra@gmail.com
> >>> <mailto:mark.chandra@gmail.com>>> wrote:
> >>>
> >>> Dear groups,
> >>>
> >>> If we said switchport voice vlan under the interface,
> >>> it's
> >>> mean the port
> >>> become a trunk ?
> >>>
> >>> When we have switchport access vlan also, which one
> >>> is tag
> >>> with vlan header
> >>> after exiting the port ? Voice vlan or data vlan ?
> >>>
> >>> Thanks group
> >>> Sent from my BlackBerry. wireless device from XL
> >>> GPRS/EDGE/3G network
> >>>
> >>>
> >>> Blogs and organic groups at http://www.ccie.net
> >>>
> >>>
> >>>
> >> _____________________________________________________________________
> >> __
> >>
> >>> Subscription information may be found at:
> >>> http://www.groupstudy.com/list/CCIELab.html
> >>>
> >>>
> >>>
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> >>>
> >>>
> >>>
> >> _____________________________________________________________________
> >> __
> >>
> >>> Subscription information may be found at:
> >>> http://www.groupstudy.com/list/CCIELab.html
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> -- Carlos G Mendioroz <tron@huapi.ba.ar
> >>> <mailto:tron@huapi.ba.ar> <mailto:tron@huapi.ba.ar
> >>> <mailto:tron@huapi.ba.ar>>>
> >>> LW7 EQI Argentina
> >>>
> >>>
> >>>
> >>> -- Carlos G Mendioroz <tron@huapi.ba.ar <mailto:
> tron@huapi.ba.ar
> >>> >>
> >>> LW7 EQI Argentina
> >>>
> >>>
> >>>
> >>
> > --
> > Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> > ______________________________________________________________________
> > _ Subscription information may be found at:
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>
>
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