There are no firewall rules that apply to the VPN traffic. The internet
connection, that the VPN passes through doesnsn't see the SMB or NFS
traffic, because they're encrypted in the tunnel packets.
Of course, but a typo is easily made and overlooked causing filtering
between the LAN and CIPE interface...
Also: ICMP traffic can be involved for routing CIPE's UDP packets...
CIPE automatically adjusts the MTU as required, but I have also tried
smaller packets, without any improvement.
The so called MTU problem is not CIPE's but other's having problems with
CIPE's 1442 or 1428 MTU.