If you find yourself in a situation where you must support multiple SIP domains, though I would seriously advise you consider the administration complexities of doing this, the following explains how to perform this.
1. Add the new SIP domain(s) to the Topology.While it’s quite common and a best practice to match the Primary SMTP domain of your users and SIP domain, this isn’t always feasible for 100% of companies
2. Create DNS records for the new simple URLs, both internal and external.
- meet.domain.com (external and internal)
- sip.domain.com (external and internal)
- SRV _sipinternaltls._tcp.domain.com 5061-> sip.domain.com (internal)
- SRV _sip._tls.domain.com 443-> sip.domain.com (external)
- SRV _sipfederationtls._tcp.domain.com 5061-> sip.domain.com (external)
3. Request new certificates for the following:
- Front End Server Certificate (internal)
- don’t forget your load balancer if you’re doing SSL offloading
- Edge Server Certificate (external)
- Reverse Proxy Certificate (external)
4. Run Enable-CSComputer on each pool member and director Server. This will re-configure IIS to accept the new simple URLs.