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Community Member

Site to Site Vlan

Hi all,

Hope you can clarify something for me.

I have inherited this config so don't shoot me!

We have 3 sites all connected by a site to site vlan with 1GB dedicated LES circuits. So on our main site (AA) vlan 10 is created with ip address 192.168.1.2 and on the remote site (BB) with have vlan 10 with ip address 192.168.1.4.

Each site has it's own VTP domain, lets call the main site AA and the remote site BB.

What I would like to is be able to do is trunk vlans that have been created in the remote site (BB) to the main site (AA).

Is there a better way to set this up other than a site to site vlan with separate VTP domains?

Kind regards,

3 REPLIES
Hall of Fame Super Silver

Re: Site to Site Vlan

Hello Jamie,

>> What I would like  to is be able to do is trunk vlans that have been created in the remote  site (BB) to the main site (AA).

do you want to waste WAN bandwidth carrying broadcast traffic everywhere?

I think that using the WAN as routed link is the best possible choice.

a real improvement would be moving to routed ports with 3 point-point links between the sites

but current scenario is better then that you are thinking of

Hope to help

Giuseppe

Community Member

Re: Site to Site Vlan

Hi Giuseppe,

Couldn't I limit the BC traffic by using the allowed VLAN command?

Plus, I can't trunk specific vlans down that link if it's a routed vlan.

J.

Hall of Fame Super Blue

Re: Site to Site Vlan

jhancockuwic wrote:

Hi Giuseppe,

Couldn't I limit the BC traffic by using the allowed VLAN command?

Plus, I can't trunk specific vlans down that link if it's a routed vlan.

J.

Jamie

Correct in both things you say but the question really is, do you need L2 adjacency between the sites ie. is there some application or cluster for example that is in both sites and needs to be L2 adjacent. By L2 adjacent i mean on the same vlan and not just the same vlan number in 2 different sites but the same actual vlan so that a broadcast in one site on that vlan goes across the link to the same vlan in the other site.

There are valid reasons for wanting/needing L2 adjacency but given the choice between L2 and L3 routed links between sites i would always look to go L3 because as Giuseppe has pointed out it cuts down on the amount of broadcast traffic.

Other benefits of routed links would be things like security in terms of a problem client in the vlan cannot affect both sites, virus control, filtering between sites etc. Note filtering between sites can be achieved with VACLs/private vlans but in my opinion L3 segregation is easier to administer.

Obviously if you did decide to go L3 then there would be some readdressing needed but if you use DHCP this can be fairly painless. So it really boils down to whether or not you really need L2 adjacency.

Jon


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