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Spanning VLANs/Subnets over a WAN link for Server Clustering (HOWTO)


I would like to cluster 2 SUN servers which are on different buildings. The two buildings are linked with a WAN connection over fiber.

The Clustering Software on the Servers (Sun CLuster 3.2) has a requirement that the two nodes/servers need to be in the same subnet for the cluster to work. My question is; how can i span a VLAN/Subnet across the two buildings over a Layer 3 connection (WAN link)?

My options are as follows:

1) Use VPN/Tunneling btwn the buildings

- How is this done??

2) Use the Sun Cluster Geocluster software

- Would like to avoid this for now

3) Please suggest another option.



Re: Spanning VLANs/Subnets over a WAN link for Server Clustering

Hi Edward,

A1: You could use EoMPLS/VLANoMPLS or L2TPv3, if your equipment/IOS does support this.

The requirement will be MPLS activation between the two sites and EoMPLS or L2TPv3 configuration.

For EoMPLS configuration have a look at "MPLS AToM: Transport, Platform, and Release Specifics" and the following chapters.

For L2TPv3 configuration have a look at "L2TPv3: Layer 2 Tunneling Protocol Version 3"

Basically you transport all ethernet/dot1Q frames between two ethernet ports over an IP or MPLS network.

Afaik MPLS will give better performance but also requires and end-to-end label switched path, i.e. changes in the transport network. L2TPv3 uses IP to tunnel the L2 frames, so in principle only endpoints need to be configured. Both technologies might give you MTU related issues because of the additional overhead, which need to be addressed in the transport network. So check the intermediate network (especially all sort of ethernet interfaces) for support of jumbo frames.

A2: you can avoid this for now using A1 ;-)

A3: DWDM across the fiber and real VLANs end-to-end. Or simple GE over the fiber with a mixture of routed and switched VLANs through a L3 switch. But A3 is just a wild guess without details regarding your topology and hardware.

Hope this helps!

Regards, Martin

Community Member

Re: Spanning VLANs/Subnets over a WAN link for Server Clustering

Is there any way to encrypt the traffic over the EoMPLS/VLANoMPLS?


Re: Spanning VLANs/Subnets over a WAN link for Server Clustering

Not sure about ur network design. But how about using IRB. You can extend ur vlan.

Check these documents:



Do rate if this helps :)

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