From: Erick B. (erickbe@yahoo.com)
Date: Sun Oct 06 2002 - 17:01:50 GMT-3
If it's a trunk port, you can't really bridge VLANs
together at L2, but need to bridge them at L3 through
a L3 interface. Under the interface configuration for
both VLANs you want to bridge together, do
bridge-group 1.
If you had SwitchA and it had VLANS 1, 2, 3 on 3
access-ports you could bridge these alltogether on
SwitchB by making 3 access-ports on SwitchB all part
of VLAN 4. Remember, VLAN definitionss are local to
the switch.
VLAN trunking headers get stripped at the ingress
trunk port, and applied at the egress trunk port.
By default on cisco gear, native VLAN isn't tagged
with dot1q (ISL tags all VLANs). There is a config
option to tag all VLANs though - so if this were on it
would be tagged. The standard specifies the primary
VLAN shouldn't be tagged I believe. Some vendors tag
all VLANs, thats why Cisco has the command to do that
so you can hook up to other vendors gear if they tag
everything. Before they added that command, you had to
just have a bogus native VLAN which causes all the
valid VLANs to be tagged thus they worked between the
different boxes.
HTH, Erick
--- Chris <clarson52@comcast.net> wrote:
> How do you bridge 2 vlans together? Doesn't the vlan
> header prevent this? I
> am thouroghly confused. If the native vlan is 1 then
> any traffic going out
> an interface in vlan 1 would get tagged upon leaving
> the interface wouldn't
> it. Whether it was the native vlan or not.
>
>
>
> ----- Original Message -----
> From: "P729" <p729@cox.net>
> To: "Chris" <clarson52@comcast.net>; "chenyan"
> <chenyan@deeptht.com.cn>;
> "ccielab" <ccielab@groupstudy.com>
> Sent: Sunday, October 06, 2002 2:05 PM
> Subject: Re: 802.1q native vlan
>
>
> > "Any untagged frames will get tagged..."
> >
> > Mmmm...sounds kinda contradictory doesn't it?
> Actually, frames assigned to
> > the native VLAN of the trunk are sent untagged
> across the trunk, period.
> But
> > one might ask, "how would the switches on each end
> know when there's a
> > native VLAN mismatch?" The answer for Cisco
> switches is through CDP. If
> CDP
> > is disabled or not available, then they wouldn't
> know and you can pretty
> > much bridge the two VLANs together and maybe not
> know it...
> >
> > Regards,
> >
> > Mas Kato
> > https://ecardfile.com/id/mkato
> > ----- Original Message -----
> > From: "Chris" <clarson52@comcast.net>
> > To: "chenyan" <chenyan@deeptht.com.cn>; "ccielab"
> <ccielab@groupstudy.com>
> > Sent: Sunday, October 06, 2002 9:48 AM
> > Subject: Re: 802.1q native vlan
> >
> >
> > Any untagged frames will get tagged to the native
> vlan and travel the
> native
> > vlan.
> >
> >
> > ----- Original Message -----
> > From: "chenyan" <chenyan@deeptht.com.cn>
> > To: "ccielab" <ccielab@groupstudy.com>
> > Sent: Sunday, October 06, 2002 11:13 AM
> > Subject: 802.1q native vlan
> >
> >
> > > hi,guys
> > >
> > > I want to know why there is native vlan for
> 802.1q and what is that for?
> > >
> > > Thanks
This archive was generated by hypermail 2.1.4 : Tue Nov 05 2002 - 08:35:40 GMT-3