Solved: Layer 2 over Layer 3

d.hodgson · ‎07-06-2009

Hi,

I'd like to have a port on my switch at our HQ on the same vlan as the server in the test network in our data centre. the link between our HQ and Data Centre is Layer 3. Is this possible?

I need to allow broadcasts from the HQ PC to be able to reach the server, this is not just for DHCP where I could use IP helper.

many thanks

Dave

Giuseppe Larosa · ‎07-07-2009

Hello Dave,

>> What about bridging?

you have already lan switches in place with lan links just make the links L2 trunks as explained in my first post.

This is your only option and you may need a maintanance window.

>> Can I use ip directed broadcast or what about using the broadcast address of the subnet as the ip helper-address?

All this doesn't help in your case

Hope to help

Giuseppe

View solution in original post

dan_track · ‎07-06-2009

Hi

You can still use ip helper-address and list the port that you have your broadcast running on. This will then unicast the broadcast to your server.

Additionally you can't send layer 2 traffic across the layer 3 network. You need change the link to a layer 2 link.

Dan

d.hodgson · ‎07-06-2009

Hi Dan,

ok so if I use "ip forward-protocol" I can add ports, but these are all forwarded to the same IP which is exactly what we want so thanks. But what if I have several servers at the test data centre? Can I somehow push a broadcast on a specific port to a different ip address?

So something like...

broadcast to DHCP goes to 10.98.0.10

broadcast to port 3000 goes to 10.98.0.11

thanks

Dave

Giuseppe Larosa · ‎07-06-2009

Hello Dave,

you need to extend the L2 vlan over the inter switch links making them L2 trunks and allowing two vlans: the L2 vlan to be extended and the L2 vlan associated to the SVI where you move the current IP subnet.

With other platforms you could use L2TPv3 or EoMPLS to have a L2 transport service over a L3 network.

Edit:

you need to do so on 3560 in HQ to 3560G link both sides

Hope to help

Giuseppe

d.hodgson · ‎07-06-2009

Can I use ip directed broadcast or what about using the broadcast address of the subnet as the ip helper-address?

I only have 3560 and 3750, not 7200 and above which are required for L2TPv3.

What about bridging?

thanks

Giuseppe Larosa · ‎07-07-2009

Hello Dave,

>> What about bridging?

you have already lan switches in place with lan links just make the links L2 trunks as explained in my first post.

This is your only option and you may need a maintanance window.

>> Can I use ip directed broadcast or what about using the broadcast address of the subnet as the ip helper-address?

All this doesn't help in your case

Hope to help

Giuseppe