Comments for Exploiting Layer 2 over Layer 3 at http://www.netcraftsmen.net , comment 1 to 4 out of 4 comments http://www.netcraftsmen.net Sat, 25 May 2013 18:54:38 +0100 FeedCreator 1.7.3 http://www.netcraftsmen.net/component/myblog/exploiting-layer-2-over-layer-3.html#comment-358 I'd need a little more info to answer that. It sounds like you have L2 over MPLS service between datacenters. If so, you could run a VLAN across -- but the risk is shared fate. That is, STP meltdown that affects both datacenters. Certainly you'd want to use traffic storm control on a Sup720 if you do that. You could also do EoMPLS. The main virtue there might be that a STP meltdown will clobber the EoMPLS device, thus rather drastically limiting the spread of the problem in the worst case. Disadvantage: arguably a bit more complex. It's the only obvious answer if you've got L3 MPLS in the middle. If you have Nexus 7000's, OTV is pretty clearly the way to go (modulo lack of support for non-multicast WAN right now, 12/1/10 -- supposedly coming soon). Yes, I drank the Cisco Kool-Aid on that. It seems to address a number of the concerns that arise with L2 between datacenters. - Pete Welcher Wed, 01 Dec 2010 04:18:22 +0100 http://www.netcraftsmen.net/component/myblog/exploiting-layer-2-over-layer-3.html#comment-357 Peter, I too need to span muliple vlans between 2 data center's for a short time as one data center migrates to the other. We have server clusters that we will break apart for the physical move, moving one of a pair, turning down the other and re-using IP space. Each site will have MPLS WAN Ethernet connectvity. So instead of running EOMPLS it would be better(easier) to add the required VLANS to the MPLS Ethernet connections at each end instead? Thank you, Stephen - Stephen Mon, 29 Nov 2010 07:52:59 +0100 http://www.netcraftsmen.net/component/myblog/exploiting-layer-2-over-layer-3.html#comment-266 I'm not understanding. If you have Ethernet, you can run a VLAN across it. That puts both data centers at risk. If you want to make it a routed link, then you get into the DCI (Data Center Interconnect) topics, including OTV, discussed in various of my blogs. That's a complex design issue, so I have to refer you to those blogs, and to what Cisco has written. BVI is process switched AFAIK, hence a really Bad Thing to do to your router CPU. Very low performance. It dates back to the 10 Mbps router days. Generally BVI is router-only as well. - Pete Welcher Mon, 27 Sep 2010 02:53:11 +0100 http://www.netcraftsmen.net/component/myblog/exploiting-layer-2-over-layer-3.html#comment-262 I need to span a vlan between 2 data center and I need to use only layer 2. Both centers are connected via ethernet. What is best way to do it? Is BVI a good solution? Thanks, - SMAIL Fri, 24 Sep 2010 10:39:00 +0100