Expressway 8.5.2+ MRA Issues

I’ve run into a couple challenges after an upgrade to Expressway/VCS 8.5.2 where MRA for phones quit working.

I found a bug that broke MRA in 8.5.2 (the recommendation has been to downgrade back to 8.5.1).  That bug is shows that it is now fixed in 8.6, so I upgraded to 8.6.1 recently.  MRA started working again, but only on one out of every three login attempts.  It was really weird.  In looking at the logs it showed a bunch of errors:

Home CUCM not available – Unknown CUCM cluster for node sub02

Home CUCM not available – Unknown CUCM cluster for node sub03

The deployment I was working on is a three node (pub and two subs), running split DNS (different internal domain than the external domain name).

After a lot of digging it turns out that there is a change in the way MRA handles CUCM lookup.  When I installed the system added my pub and subs to Expressway-C by IP address.  But it looks like Expressway now attempts to communicate with them via hostname, and not IP as they were defined by me.

Since Expressway is using the domain suffix assigned to MRA (, it is attempting to lookup and  I didn’t have A records for these on my internal DNS server extdomain zone since I’ve never needed to resolve them by the external domain name.

Adding these two records fixed the login issue and it now logins on first attempt like it used to.