Periodic Ping Increase... Has anyone seen something like this before and can offer advice to track it down?
I'm no idea what the cause is so I've posted in general internet.
I've noticed this since I signed up to ThinkBroadband's pinging service, after going onto FTTC. See the graph:
About every 1.5 hours (but not exactly - actually 17 times in 24 hours) I get the latency increase as can be seen. It seems consistently timed at just after midnight every night. Note also the little pre-spike before the big ones. Obviously there's a little variation when I'm using something.
Last night I turned off my server and most kit around here, or at least disabled their gateways if they had one set. So, nothing should have been going out. I monitoring the switch port connected to my router's LAN port with Wireshark using a dedicated monitor NIC on the PC, with the LAN NIC disabled (so it was quiet). Nothing showed that could account for the increased latency; hardly any traffic, just the usual network chatter (STP, CDP, etc). Nothing tried to use the internet.
That leaves just the router and modem themselves (see my sig). There's nothing I know of on the router's config that should be running periodically like that. The router terminates an HE IPv6 tunnel but I've not noticed anything odd with that before.
My next step is to start disabling services on the router and monitoring the WAN port directly, but that needs a trip into the loft later today to swap some cables around.