Cannot Contact a DC from another DC

Hi, I have a strange issue which hopefully you can help me with. I'm not sure if it's me being daft but I have 7 DC's all connected using the same model firewall/routers through IPSEC VPN tunnel at different sites, on different subnets and everything all talks to each fine, except the other day I found that from the DC01 I could not unc or contact DC03. I did a ping to both the NetBIOS name, FQDN and the IP but it would not contact the server. All other servers will talk to DC03 and DC03 will talk to all the other DCs including DC01, I can even ping from any client on the same subnet that DC01 is on and it finds DC03 no problem. I can even ping other things on the subnet of DC03 from DC01 and it will contact them without issue. It's just DC01 to DC03 one way will not talk whatsoever. This happened before and it went away over night but it's now come back with a vengeance and I cannot see what's happening!!?? Please any help would be most appreciated. Also wanted to mention that the Windows Domain Firewall is switched off.
Dave BIT ManagerAsked:
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CompProbSolvCommented:
Are you pinging successfully with both ipV4 and ipV6?
AkinsdNetwork AdministratorCommented:
Interesting and strange.

There are several options to try. Try pinging after each step to see if problem goes away
1. Run ipconfig /flushdns on both DCs
2. Clear the mac address table on the distribution switch.
3. Run dcdiag /fix from any domain controller
4. Reset the NIC on both servers
- netsh winsock reset
- netsh int ip reset

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Dave BIT ManagerAuthor Commented:
Hi,
I did the above and rebooted the server also which solved the issue. Hopefully it won't happen again.
Thanks
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