Federation utilizes the SRV DNS record with a specific format, and for this, you can use the good old nslookup utility.
In this example, we are looking for the Federation SIP Address for microsoft.com. The result is sipfed,microsoft.com
> set q=srv
DNS request timed out.
timeout was 2 seconds.
_sipfederationtls._tcp.microsoft.com SRV service location:
priority = 0
weight = 0
port = 5061
svr hostname = sipfed.microsoft.com
Looking at the example, the federation sip address always starts with _sipfederationtls._tcp. and followed by the actual domain.