[c-nsp] Vlan and subinterface

[Tom Storey]

Ive never used one without configuring a VLAN on it, and to the best of my
knowledge it has never been possible, so I would say yes you do need to
specify a VLAN. Subinterfaces provide logical boundaries between broadcast
domains. On Linux they might serve another purpose, but IOS aint Linux. ;-)

If you simply want multiple subnets in the same broadcast domain, forget
what you know about Linux and how you would do it there, and just apply the
additional subnets using the secondary keyword as per Tony's example. :-)

If youre serving a number of customers, and each customer is delivered in
their own VLAN (i.e. to keep them separate from each other - basic
security), then yes, most likely a subinterface is what you want, and you
will need to configure a VLAN ID on that subinterface. You can then
configure the subnet for each customer on their respective subinterface.

e.g.

GigabitEthernet0/1.10
 encapsulation dot1q 10
 description Customer 1
 ip address 192.168.0.1 255.255.255.252
!
GigabitEthernet0/1.11
 encapsulation dot1q 11
 description Customer 2
 ip address 192.168.0.5 255.255.255.252
 ip address 192.168.0.9 255.255.255.252 secondary
!
GigabitEthernet0/1.12
 encapsulation dot1q 12
 description Customer 3
 ip address 192.168.0.13 255.255.255.252
!

etc etc

And naturally Gi0/1 needs to be connected via a trunk to a device like a
switch so that those VLANs can be fanned out to individual ports, or
perhaps trunked to another switch.

Tom

On 24 December 2011 07:09, ujjwal maghaiya <ujjwal_12 at hotmail.com> wrote:

>
> what is VLAN necessary inorder to create sub interface.
>
>
>
>
> Date: Fri, 23 Dec 2011 10:22:42 -0500
> Subject: Re: [c-nsp] Vlan and subinterface
> From: ttauber at 1-4-5.net
> To: ujjwal_12 at hotmail.com
> CC: cisco-nsp at puck.nether.net
>
> No, you can configure multiple subnets as secondary IP addresses like this:
>
> !
> interface gigabitEthernet 1/1
>  ip address 192.0.2.1 255.255.255.240
>  ip address 192.0.2.193 255.255.255.224 secondary
>  ip address 203.0.113.65 255.255.255.192 secondary
> !
>
> I'm not positive what you meant.
>
> Tony
>
>
> On Fri, Dec 23, 2011 at 6:43 AM, ujjwal maghaiya <ujjwal_12 at hotmail.com>
> wrote:
>
>
> Dears,
>
> Just a confusion.
> is it necessary to confiugre VLAN if i want to configure multiple
> subinterfaces with different SUBNETS in single physical interface.
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