Cisco Systems A question about default vlan

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Subject Author Date
A question about default vlan aaabbb16 07-02-08
Posted by on July 2, 2008, 7:43 pm
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Suppose I have a new cisco switch and all ports are belong to vlan 1.
I use "interface0/1 switchport access vlan=90"
Does this interface0/1 still belong to vlan 1
or just belong to vlan 90 only?
TIA,
st

Posted by Doug McIntyre on July 2, 2008, 11:05 pm
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aaabbb16@hotmail.com writes:
>Suppose I have a new cisco switch and all ports are belong to vlan 1.
>I use "interface0/1 switchport access vlan=90"
>Does this interface0/1 still belong to vlan 1
>or just belong to vlan 90 only?

Interfaces can only belong to one VLAN. (at least with anything in
recent history). If you put an interface into VLAN90, it belongs to VLAN90..



Posted by Trendkill on July 3, 2008, 7:43 am
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> aaabb...@hotmail.com writes:
> >Suppose I have a new cisco switch and all ports are belong to vlan 1.
> >I use "interface0/1 switchport access vlan=3D90"
> >Does this interface0/1 still belong to vlan 1
> >or just belong to vlan 90 only?
>
> Interfaces can only belong to one VLAN. (at least with anything in
> recent history). If you put an interface into VLAN90, it belongs to VLAN9=
0..

Unless you leave it in vlan 1 and then configure as a trunk. Then
your statement is still accurate, but its not apparent that the native
vlan of the trunk is vlan 1 since its not an access port. It does
show up in show trunk though. But as for access ports, you can only
be a member of one vlan, except for secondary vlans, which are still
technically a type of tagging.

Posted by Walter Roberson on July 4, 2008, 10:34 am
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>aaabbb16@hotmail.com writes:
>>Suppose I have a new cisco switch and all ports are belong to vlan 1.
>>I use "interface0/1 switchport access vlan=90"
>>Does this interface0/1 still belong to vlan 1
>>or just belong to vlan 90 only?
>
>Interfaces can only belong to one VLAN. (at least with anything in
>recent history).

Possibly that is true with Cisco equipment (I don't know), but it
is not true in general. For example the Nortel Baystack line of
switches allow one to assign VLANs according to packet protocol
in a number of ways -- .e.g, 802.2 vs 802.3 vs SNAP.

I -have- run into switches that allowed one to assign multiple port-
based VLANs to the same port. What that -means-, exactly, in terms
of the theory of what VLANs -are-, is not clear; I believe the practice
on the devices I saw was that packets originating from any of the
VLANs could be delivered to the same port, and that packets heading
out of the port would be assigned into a VLAN according to the
VLAN entry the destination MAC. Yes, this -would- have problems if
the same MAC represented different devices on different VLANs, as
is legal. The practical use of assigning multiple port-based
VLANs to a port appeared to be to allow you to hang a server on
the multiply-assigned port and have it able to talk to clients in
several VLANs, with those clients not able to talk to each other
directly, without the trouble of having to use multiple physical
interfaces for the server or the trouble of configuring the server
NIC as a trunk port.

Posted by on July 11, 2008, 9:16 pm
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On 7=D4=C24=C8=D5, =C9=CF=CE=E77=CA=B134=B7=D6, rober...@hushmail.com (Walt=
er Roberson) wrote:
>
> >aaabb...@hotmail.com writes:
> >>Suppose I have a new cisco switch and all ports are belong to vlan 1.
> >>I use "interface0/1 switchport access vlan=3D90"
> >>Does this interface0/1 still belong to vlan 1
> >>or just belong to vlan 90 only?
>
> >Interfaces can only belong to one VLAN. (at least with anything in
> >recent history).
>
> Possibly that is true with Cisco equipment (I don't know), but it
> is not true in general. For example the Nortel Baystack line of
> switches allow one to assign VLANs according to packet protocol
> in a number of ways -- .e.g, 802.2 vs 802.3 vs SNAP.
>
> I -have- run into switches that allowed one to assign multiple port-
> based VLANs to the same port. What that -means-, exactly, in terms
> of the theory of what VLANs -are-, is not clear; I believe the practice
> on the devices I saw was that packets originating from any of the
> VLANs could be delivered to the same port, and that packets heading
> out of the port would be assigned into a VLAN according to the
> VLAN entry the destination MAC. Yes, this -would- have problems if
> the same MAC represented different devices on different VLANs, as
> is legal. The practical use of assigning multiple port-based
> VLANs to a port appeared to be to allow you to hang a server on
> the multiply-assigned port and have it able to talk to clients in
> several VLANs, with those clients not able to talk to each other
> directly, without the trouble of having to use multiple physical
> interfaces for the server or the trouble of configuring the server
> NIC as a trunk port.

How to config a access port with multiple Vlan using cisco switch?

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