E.g. if a site is not listed as 'siteList' in the siteLink object
samba_kcc silently doesn't replicate with any other server,
thinks like these are very hard to debug.
samba_kcc --debug gives too much information for a normal administrator
to find the problem.
It would be good to have an output like this:
Intrasite DC=MYNAME SITE=MYSITE:
DC1[online], DC2[WERR_HOST_UNREACHABLE], MYNAME, DC3[online], DC4[online], DC5[online], DC6[online], DC7[online], DC8[online]
Selecting by ring topology: DC1, DC3
Optimizing connection(s) to: DC6
Intersite replication required for the following Transport/Links:
DC1[auto], DC2[WERR_HOST_UNREACHABLE], MYNAME, DC3[online], DC4[online], DC5[online], DC6[online], DC7[online], DC8[online]
SITE1, SITE2, SITE3, MYSITE, SITE4, SITE5, SITE6, SITE7, SITE8
Selecting by ring topology: SITE3/DC37[auto], SITE4/DC42[preferred]
Adding optimizing connection(s) to: SITE8/DC85[preferred]
MYNAME=>DC3 adding DC=newdomain,DC=addom,DC=example,DC=com
MYNAME=>DC1 for DC=... and DC=Schema, ...
MYNAME=>DC6 for DC=... and DC=Schema, ...
Found non-autogenerated connections:
Sync connections to repsFrom/repsTo:
Update repsFrom DC3
Remove repsFrom DC2
Add repsFrom DC3
I hope you got the idea.
The idea if that someone reading "How Active Directory Replication Topology Works" https://technet.microsoft.com/en-us/library/cc755994(v=ws.10).aspx
has a chance to understand what's going on.