Expressway HA Cluster Design

[rchaseling]

Hi,

I have an Expressway design question(s) that I would like some clarity on.

Deploying an Expressway install for a customer that has 2 x datacentres with pretty much the same setup in both - the customer will be using MRA and Telepresene.The plan is to put an Expressway C & E in both Datacentres (as per diagram attached) and a CUCM cluster split between the two datacentres

The requirement from the customer is that ALL traffic must ALWAYS traverse the Primary datacentre and only if this datacentre goes offline is traffic then  use the Secondary Datacentre

If I'm reading the guides correctly if I create an Expressway cluster all nodes must be able to route to all other nodes in the cluster......what I don't want is for Expressway C in Primary Datacentre  to route any traffic to Expressway E in Backup Datacentre  or similar / vice versa......or CUCM to route any traffic to Expressway C in Backup datacentre (unless primary is offline)

1) Do I need to setup a cluster at all? ie do I just have technically 2 standalone C&E deployments using DNS SRV and SIP trunk Route List priority to always send calls to Primary Datacentre Expressway?

2) Is it only Expressway C's can be clustered with Expressway C's or can a cluster contain Cs and E's?

Thanks in advance

[Lawrence James]

2) Clusters can only contain the same type of devices. to cluster across datacenters you must meet the 30ms roundtrip hop time, etc.. constraints.

In your case your DNS entries for the cluster and nodes within the cluster will need to determine the datacenter that is used - when  you enter the DNS records you will need to give the DC1 node(s) a higher priority than DC2 node(s).

Do you need a cluster - Yes. For one It is better to have the cluster than not and I think you need it in order to seamlessly roll over to DC2. Also the config for DNS will be relatively the same regardless if you have a cluster or not.

See the VCS cluster guide and where they tell you to make the weighting the same this is where you will change the weighting and priority to fit your requirements.

Another option is to use a NLB and have the logic in the NLB take care of it.