FRS and host files

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Just a quick blog post about something I saw recently. I was at a customer site performing an ADRAP and I ran into one of the customer’s domains where FRS was not converging. Among the troubleshooting steps I tried to verify that DNS had records for the DCs which it did and I verified using nslookup from the ADRAP machine I was using for gathering data from the DCs.

To cut a long story short the customer had a host file on the DCs of that domain in the following format.

10.1.1.1 DC1 DC1.Domain.Com

10.2.3.1 DC2 DC1.Domain.Com

As both IP addresses were bound to the same FQDN, FRS on each DC was having issues pulling updates from its partner. However AD replication was working fine. The reason for this is the DCs were using the <GUID>._msdcs.forestFQDN and therefore DNS was resolving the record.

Note to self, when troubleshooting name resolution always do the test from the host machine directly.

HTH

M