From: navaid@rogers.com
Date: Fri Sep 05 2003 - 15:55:13 GMT-3
So far I have developed following understanding:
Default on cisco switches is to use PVSTP (per vlan spaning tree). Therefore different ports can be in different native vlans.
For ISL trunking you don't need same native vlan on both side but for dot1q you need same native vlan on both devices.
switchport mode trunk
will for the port to be a trunk and we need to configure native vlan.
switchport access vlan 110
is acceptable to define the default port vlan if mode is not forced to trunk. (if trunk go with native).
Please correct if any of above statement if incorrect.
Thanks,
Navaid
>
> From: "McClure, Allen" <Allen.McClure@Yum.com>
> Date: 2003/09/05 Fri PM 12:25:53 EDT
> To: <boby2kusa@hotmail.com>, "ccie2be" <ccie2be@nyc.rr.com>,
> "Group
> Study" <ccielab@groupstudy.com>
> Subject: RE: 3550 and IP Phone Verification
>
> For 802.1q phones, this should be the appropriate configuration. In my
> experience access subcommands (switchport access xxxxx) do not come into
> play when the mode of a port set to trunk.
>
> http://www.cisco.com/en/US/customer/tech/tk648/tk361/technologies_tech_n
> ote09186a0080114aee.shtml
>
> interface FastEthernet0/13
> description phone and PC
> switchport mode trunk
> ! Negotiation = bad for lab IMO. In RL it may be needed for
> flexibility.
> switchport trunk encapsulation dot1q
> ! If a phone talks trunking, it's dot1q, not ISL
> switchport voice vlan 110
> ! Voice traffic on vlan 110
> switchport trunk native vlan 10
> ! Data traffic on vlan 10 (native = untagged). Change this to change
> vlans for the PC.
>
> Matching the current PC access vlans of this firm with the native vlan
> config should solve your issue. The native vlan is only significant to
> the two ports forming the trunk and can thus be changed port by port.
>
> I've been wrestling with this for a while myself and this is my current
> solution. Any feedback is appreciated. Certainly would love to be
> corrected if I'm wrong.
>
> Allen G. McClure
> CCNP/CCDP/MCSE
> Yum! Brands, Inc.
> Sr. Network Analyst
> allen.mcclure@yum.com
>
>
> -----Original Message-----
> From: boby2kusa@hotmail.com [mailto:boby2kusa@hotmail.com]
> Sent: Friday, September 05, 2003 10:58 AM
> To: ccie2be; Group Study
> Subject: Re: 3550 and IP Phone Verification
>
>
> 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@nyc.rr.com>
> To: "Group Study" <ccielab@groupstudy.com>
> 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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