Single IP Subnet provision for intersites

Unanswered Question
Feb 6th, 2007

Dear All,

Our company has decided to migrate from Exchange 2003 to Exchange 2007 messaging system. The network requirements of Exchange 2007 high availability cluster (Continuous cluster replication)as below:

The private network connections between cluster nodes must appear as a single, non-routed LAN .In this case, the connections network must be able to provide a guaranteed, maximum round-trip latency between nodes of no more than 500 milliseconds. The Cluster Interconnect must appear as a standard LAN.

We have no problem in getting round trip delay of not more than 500ms. But we need to explore the possible ways to provide single IP subnet over inter sites for cluster requirements.

Does IRB (Integrated Routing and bridging) help??? Or Which other WAN technology provides same IP subnet between two geologically separates sites?

Please suggest.

I have this problem too.
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sachinraja Tue, 02/06/2007 - 03:55

How about these ??

1) Any Transport over MPLS (ATOM)

2) L2 Metro Ethernets - having the same VLAN both the ends, and having the WAN as L2 trunks...

These are more commonly used !!!


anwar.shariff Tue, 02/06/2007 - 04:29

Hello Rajm

Our WAN network do not have MPLS as of now. can you send more description on L2 metro ethernets with probable configuration scenarios.

Really appreciate the reply.

thanking you

sachinraja Tue, 02/06/2007 - 15:11

Hello Anwar,

COnfigurations on L2 ME will be the same as any Layer 2 network, at your end.. at the ISP end there are a lot of tunneling configured, to carry the vlan information across the network... they can also run VPLS if you want a multipoint to multipoint metro ethernet configuration... I think this is really not required... the ISP will take care of this...

Anyway, at your end, you will be given a copper or fiber link which you can terminate in any L2/L3 switch... you just need to configure the standard commands for trunking, VLANs, VTP , STP etc, as you will configure if the links were between switches in the same building.. the L2 link given by the ISP should be really transparent and should not be blocking key data streams like BPDU, VTP etc.....

Hope this helps.. all the best.. rate replies if found useful..


sachinraja Tue, 02/06/2007 - 15:13

Ethernet Over SDH is also another popular option that i missed out..can you please talk to your local ISP and find out the relevant details (on cost, termination etc) ?


anwar.shariff Tue, 02/06/2007 - 22:15

Hello Raj,

In L2 ME case, what type of WAN connectivity I should be asking to ISP? Here in my country ATM links, Serial leaselines( v.35) are available technologies.

what type of interface module my L3 switch should have ?

Can you suggest me any links for VLAN configurations with similar commands,I need to pass to my subordinates...

thansk a lot


sachinraja Tue, 02/06/2007 - 22:34

Hello Anwar,

For all the technologies that i was talking , the WAN interface needs to be a fasteth or Gig e, either a copper or a fiber (depending on what the ISP provides).. Ask your ISP any kind of Layer 2 link across the WAN.. you can ask them specifically for the technologies discussed above.. you need not have a ATM or serial module in ethernet based technologies... You can refer to this URL for configuring VLANs.. it is much the same that you configure for a normal LAN switch:

Hope this helps.. all the best..



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