Replication issue

[rob101]

I have a domain controller problem that I can't seem to find a solution to.

 

I have two sites all on one domain connected over a VPN tunnel, with 4 domain controllers total, I'm getting the following errors ndc02 is reporting error 55 sdc02 and 55 sdc01 then when i run repadmin /repsummery on sdc01 abd sdc02 i get error 58 to ndc02

 

 

Replication looks ok as its likely going though ndc01 which is the PDC.

 

I can ping the servers and resolve them through DNS, ports look ok using port query.

 

Can anyone give me some ideas to look at or try, please?

[willtech]

do you get any errors in DCDiag ?

[HPlum78]

https://www.microsoft.com/en-gb/download/details.aspx?id=30005

 

Get that tool.

[rob101]

Dcdiag stops on knows of role holders on both sdc01 and sdc02, a check in AD at operation masters reports correctly but i get an error when i check infrastructure, operations master error. these are all on both sdc01 and sdc02, ndc01 is reporting no errors.

[rob101]

Just used port query to take a look at port 389, ndc02 to both sdc01 and sdc02 is fine, sdc01 and sdc02 to ndc02 fail on port 389 via tcp but get though on 389 udp. Firewalls are off at both ends, what the hell would stop this other than a firewall somewhere?

[willtech]

I would have a look at what is doing your vpn to see if you can see the traffic passing. have a look at the route the system takes by doing trace route and see if their is any devices in the route that is stopping the traffic.

[rob101]

Just found out the VPN has a low MTU value set at 1380, can domain controllers replicate with a lower MTU or is domain traffic always marked at do no fragment, its strange how the port test is working on other servers but not between these 3.

 

Can I force the DC's to use a lower MTU for communication?