Connection: Comcast cable modem (signal on the modem is fine) 500d/18u
Mikrotik Device: RB4011iGS+RM
Issue:
I have been having this issue for days. It is really slowing down DNS. LAN topology is really simple and working fine as I know. The latency jumps through the roof and back down at the modem. According to a browser based test they are dropped or arrive really late.
Basic Configuration:
I have basic forward chain port based packet matching for common protocols including DNS putting them into a global->high,med,low priority simple queue tree (mimicking Pfsense). Most importantly the queues show no dropped packets and the mangle rule matches them (ICMP) and puts them in the highest priority queue. I’ve asked everyone that I know who would know anything about networking and they are at a loss. It’s almost like there’s two conflicting gateways and the start of the connection is just getting routed into the ether. Long term connections like video and games etc work fine once they’re established.
I’ll mention, just in case you might be unaware, that any queue priorities you assign traffic are entirely internal to the RouterBoard, and get discarded when the traffic exits an interface. So, if the problem is indeed at or in the modem, priorities won’t solve it.
Have you run a traceroute instead of a ping, to try to identify which node in the path is responsible for the abysmal delay on the first attempt? If the delay is outside your network, playing with stuff inside your network won’t address it.
Can you observe the same high latency when you ping directly from your Mikrotik router? How about other machines connected to the router? Do you have arp enabled on your internal interfaces/bridges?
I recall seeing such behavior on infected machines and networks with arp poisoning.
I was going to include a traceroute to Google but I was waiting for the post to be approved. Sorry for taking 4 days I thought the system emailed when approved. The issue was at the modem. Due to reasons that I don’t know the status page was REALLY slow and the modem was overwhelmed with very little traffic causing the weird delays. Swapping the modem for a newer model Comcast wanted us to have anyways resolved the issue as far as I can tell.