I manage two sites that are connected via an IPSEC Tunnel with IPFire routers on both sides managing the VPN. I have a Synology backup appliance on the local lan, and on the remote site. Backups work perfect with no issues from local servers to the local synology, but then the Snapshot replication to the remote site’s Synology has been spotty, and hit or miss. The snapshot replication app just seems to stall with no error messages. After fighting these issues for a year with Synology they keep coming back saying that they are seeing lots of timeout and is claiming that our network is “unstable”. I can regularly ping all switches, the local IPFire, the remote IPFire, the remote synology, the local synology without any issues. I’ve run wireshark captures and I can’t find any problems. I started running an EMCO ping monitor session on both sides to check and log network activity from both sides of the network to watch for outages. I know there have been some issues with DNS that have affected things at times, but nothing to warrant a constant struggle to get backups to transfer over as they claim. I don’t see anything of concern in /var/log/messages, The synology device on both sides are connecting by IP not by name, so I don’t think DNS is a factor.
I’m looking for ideas on what to check or what to watch for. If this was your network and your situation what would you watch for or check to validate / disprove their ‘network is unstable’ claim?