Connecting 2 bulding with different VLAN

[naive.naive]

Hi,

Currently, there are 2 different building running on separate VLAN, which want to merged (meaning they want to be able to connect to each other via a fiber link)

1) Building A - flat LAN, with 2 subnets

2) Building B - multiple VLAN exists (L3)

May I know, what's the recommended method to merge this 2 network.

Thanks.

[pkhatri]

Hi,

One very simple way is to configure a new VLAN on the switch in Building B and then make the port on that switch that connects to Building A an access port in that VLAN.

That method will result in the least amount of configuration effort.

You will also need to enable inter-vlan routing on the switch in building B if it is L3 capable. Otherwise, you will need a router to do so.

Pls do remember to rate posts.

Paresh

[naive.naive]

i thought the best way, will be mirroring the VLANs in building A & B (ensuring both buildings having the same VLAN) and create a trunk between them.

[pkhatri]

Oh okay, I had assumed that the traffic in building one was supposed to be for a distinct VLAN.

But if you wish to merge them, then I agree that you need to mirror the VLANs in building A, create a trunk on the link between them and perform inter-vlan routing to get between the VLANs.

Pls do remember to rate posts.

Paresh

[naive.naive]

i've another question, with the new VLANs being created for both buildings, will the traffic be a lot (coz i don't want unnecessary traffic to pass thru).

secondly, i know a vlan can have multiple ip subnets, but does that apply to hsrp also??

[pkhatri]

To minimise the amount of unnecessary traffic over the trunk, I would recommend that you configure both switches for inter-vlan routing so that that can be done locally if the source/destination are at the same site.

You can use HSRP with secondary IP addresses as it does support multiple subnets per VLAN.

Pls do remember to rate posts.

Paresh

[naive.naive]

meaning i've to create all hsrp on all the L3 for both buildings..

below are valid ??

int vlan 1

ip add 10.10.10.1 255.255.0.0

ip add 20.20.20.1 255.255.0.0 secondary

standby 1 ip 10.10.10.254

standby 1 ip 20.20.20.254 secondary

[pkhatri]

Yes, that would work.

Paresh