data center interconnect Lan span over Wan

Unanswered Question
Jul 23rd, 2009


I am working on a project for data center migration. I would like to know the design solutions and their comparisons for DCI.

For example,

1)Which solution is best: Using L2 extension over L3 or using L3 to interconnect two DCs.

2) Retaining the L2 domains at each data center or using IP?

Can anybody guide me to the link or PDF which talks about the pro's and con's of each solution?

thanks in advance,

shri :)

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Overall Rating: 3.5 (2 ratings)
shrikardange Thu, 07/23/2009 - 21:52

Hi Giuseppe

Thanks for the URL. I had already went through it but it does not talk much about interconnecting two DCs.

I appreciate your view on retaining two separate L2 domains at each DC.

I need to extend L2 to other DC for applications in a DC. I want a comparison chart on which method is best for such interconnectivity : Lan span over Wan or changing IP addreses and having L3 connectivity.


Giuseppe Larosa Thu, 07/23/2009 - 23:43

Hello Shrikar,

if possible a NAT approach should be preferred and would allow to use a L3 only interconnect.

Each server moved to new DC could have a NAT entry to hide its move from other devices in old DC that will try to access it.

This works for access from other IP subnets.

If there are clustering communication needs that lie on L2 connectivity you may need to extend some L2 vlans over the interconnect.

What can be the best wat to achieve this depends on the devices you use, expected traffic volume.

Solutions can be:

L2TPv3 tunnel between L3 devices carrying a subset of vlans

or it can be an idea to use 802.1 Q in Q if devices are only multilayer switches.

Another option could be to use EoMPLS between MPLS capable multilayer switches.

As I wrote in my first post I would try to avoid to join the two L2 domains.

For great traffic volumes Q in Q or EoMPLS have to be preferred.

It also depends on the type of interconnect if it is dark fiber q in q can be an option if there is a service provider providing IP connectivity L2TPv3 can be the only feasible solution.

If the service can be a form of MPLS service like carrier supporting carrier EoMPLS can be deployed (some care for MTU issues in this case).

Hope to help


shrikardange Fri, 07/24/2009 - 00:09

Hi Giuseppe,

Thanks for the suggestions. All of them are very helpful.

I am thinking of some L2 connectivity for some applications where L3 is not feasible. Q-in-Q suits best in my scenario.I am also exploring VPLS with my service provider. For L2TPv3, I need to dig more which applications it can support and which application I have in DC. That is the main reason I need to compare all of the solutions and recomond best to the client.




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