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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