[afnog] Fw: Re: how to aconfigure a vlan

Tue Nov 17 05:43:23 UTC 2009

Thank u Mark for helping me and i appreciate ur fast response.
hoping u will help me further, i will elaboret my problem a bit.

we have three capuses. two of the campuses have cisco 6509 switches and the other campus has a cisco 4506 switch as core switches. all the intercampus liks are optical fiber which are in a triangular fashion and are all owned by our university. all the links are working. in the main campuse, there are 15 VLANs (subents) created on 6509 core switch (all other L2 switches in all campuses are cisco 2950 and 2960). so in the main campus, it is only the 6509 switch which is in vtp server mode.
and in the other campuses, the core switches are in vtp mode server, where as the other switches are in client modes. we use rip v2 as routing protocol to communicate each subnet in one capuse with others in other
 campuses.

in the main campuse, we use an addess space of 10.128.0.0/16, and on the other campuses, we use 10.129.0.0/16, and 10.130.0.0/16. 

so, when we want to create a new vlan on any of the campuses, we just create it on the respective core switch. so, right now, i don't have any problem in creating a working vlan with the architecture i am telling u now.

here is the problem i faced.

i am asked to create one vlan with a network id of 192.168.20.0/24. computers in this valn don't need to be connected to the Internet but should communicate with each other being at different campuses but the servers that the computers are connected to will be connected to the university network and hence to the Internet. so, this vlan should be vissible in the 10.128.0.0/16 campuse and in the 10.130.0.0/16 campuse. remember that all my core switches are vtp server b/c they handle their own vlans in thier respective campuses and the intercampus links are routed links with thier own subents. so, my problem how to propagate the 192.168.20.0/24 vlan id on the routed link.

thank u for ur help.
Teklay

--- On Sat, 11/14/09, Mark Tinka <mtinka at globaltransit.net> wrote:

From: Mark Tinka <mtinka at globaltransit.net>
Subject: Re: [afnog] how can to aconfigure a vlan
To: "teklay gebremichael" <teklish76 at yahoo.com>
Cc: afnog at afnog.org
Date: Saturday, November 14, 2009, 11:08 AM

On Saturday 14 November 2009 07:16:04 pm teklay gebremichael

wrote:

> but now i want to creat a vlan which has one subnet
> address and that is visible across all the campuses (i.e
> a VLAN spanning all the campuses).
>
> can any one help me how can start that?

First you'll need to interconnect all the 3 Ethernet 
switches. Do you have your own connectivity between them, or 
will you be leasing it? If you'll be leasing it, there are a 
number of considerations to make. If it's your own network, 
life will be easier.

Next, the easiest thing to do to create a broadcast network 
spanning all 3 sites is to implement 802.1Q VLAN Trunking 
across all the core links. Once you configure a VLAN ID on 
one switch, configure it on all others where you need to 
VLAN to end up, and ensure the 802.1Q trunk interfaces are 
configured to forward all traffic being handled by that VLAN 
ID. Stay away from things like VTP, though (the Ethernet

switches should run in VTP Transparent mode).

Cheers,

Mark.

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