DC connectivity

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Mar 12th, 2009
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Hello all,

There are 2 data centers which need to be interconnected.

Each data center equipped with 6500 switches.coppper connectivity avaliable b/w switches.

4 Vlans exist in data center1 with interface Vlans configured on FWSM.all desktops have FWSM interface as gateway.

2 Vlans exist in data center2 with interface vlans configured on switch.

our requirement is to connect these two data centers and make communication between the data center Vlans possible.

Can you suggest the best approach to acheive this.

attached the figure for info and let me know if anythng more needed.



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Overall Rating: 4 (2 ratings)
Jon Marshall Thu, 03/12/2009 - 06:34
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There is not a lot of information in what you want to do other than simply connect the 2 data centres up.

Based on that, and assuming there is no need to have the same vlan in both DC's i would make the links between the data DC's routed links either 2 separate links or a L3 etherchannel as it looks like you have 2 individual connections.

Perhaps if you filled in a bit more detail we could suggest more.


senthuran Thu, 03/12/2009 - 06:51
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Thanks Jon and your assumptions are correct.

We need to connect the 2 data centres and your suggestion are much helpful.

I wanted to know how does the communication b/w the vlans takesplace in these scenario with

enduser at Data centre 1 has gateway pointed to FWSM interface(dont have much idea how FWSM behave).

Thanks again.

Jon Marshall Thu, 03/12/2009 - 06:57
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It depends on how you have configured the FWSM. A common setup would be that there is an outside interface on the FWSM that connects to the MSFC on the 6500. All the user vlans are on separate interfaces on the FWSM.

So what you should be able to do is have a routed link between the 2 6500's on the MSFC's. You could also use a routing protocol eg EIGRP between the 2 6500 switches.

That way vlan 101 & 102 would be learnt via EIGRP. The 4 vlans behind the FWSM will need to be advertised to DC2.

How you do this depends on how you are routing this now. Do you have static routes on DC1 6500 for these subnets pointing to the outside interface of the FWSM ?. If so you can simply redistribute these into EIGRP.

You may be running OSPF between the MSFC and the FWSM in which case it makes more sense to run OSPF between DC's.

Apologies for being a bit vague but there are a number of ways the FWSM could be setup and without knowing exactly how it has been done it's not possible to give you a precise answer.


senthuran Thu, 03/12/2009 - 07:33
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Thanks again jon.much appreciated.

I have to accept that i don't have much info on that.Its in remote side and possibly by tomorrow shoud get some info on that.

I will post the info after i get it.


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