MRA - How does Expressway-C choose a Call Manager

[Bill]

I am wondering how Epxressway-C decides which Call Manager to authenticate user's against.

I thought it might use weights from the internal DNS for _Cisco-UDS, but it does not seem to.

I am looking for a workaroundto an issue.

One CUCM server has DNS/Domain issues, and when Exp-C tries to authenticate a user against this CUCM, it fails.

It it chooses a different CUCM server it works.

I know the correct fix is to fix the root of the problem.

But raises the question - How does Exp-C decide which CUCM it uses?

[Jaime Valencia]

It uses _cisco-uds for internal resolution, if it's a multi-cluster environment and several clusters share the same domain, it will also rely on ILS in case the user is not found in the cluster where _cisco-uds is pointing to.

[Bill]

Thank you Jaime

I have set DNS SRV priority for the Sub to be less preferred (higher value) than the Pub, but it still often times wants to use the Sub.

I am seeing this in the Exp-C log:

Unable to determine home CUCM
Reason="Unknown CUCM cluster for node"
Node=sub1.localdomain

localdomain is not the correct domain.

But I cannot change it now.

So I was hoping i could just change the DNS priority and force Exp-C to use the Pub, which has correct Domain name.

Working around the issue is probably more effort than just fixing it.

[Roger Kallberg]

One suggestion would be to temporary remove the SRV record for the faulty CM node until you get around to fix the underlying problem with it.

[Bill]

Good suggestion Roger.

We ended up fixing the underlying issue and renamed the Call Manager's domain.

Thanks