Unity and GC

[ciscoforum]

If I have two offices cross a highspeed WAN network and each office has a DC/GC and Unity. Do I really need use AD sites? What will happen if one of the Unity happen to use the other office GC? Thanks

[Hin Lee]

The reason to use sites is so that ip-traffic that can stay local does not eat up the bandwidth across the wan. If the local-GC does not respond, windows will go across the wan to query the WAN-GC but without sites configured, there is no guarantee which LDAP/GC server will be used.

[Tommer Catlin]

Exactly what hinho said. If you use sites with AD between WAN links, it will cut down on AD traffic and free up bandwidth. If your Sites are small (less than 50) and you have a large bandwidth, it would not be so bad. But MS rule of thumb is always use Sites between WAN links. It's fairly easy to setup and lets you cut down on AD replication times, AD calls, etc. Since Unity is integrated closely with AD.. it makes sense to use Sites.