Capturing packets from ISP side of router
I'm having an issue where intermittently DNS requests time out. I have the standard ISP cable connection, a modem and a Linksys Mesh router. Most of the time everything is working fine. Good download speed, no issues connecting to internet web sites and all. Intermittently, I get the error that a website can't be found. When I jump into a cmd window, and issue a nslookup to a node at my ISP, the requests timeout. If I use the ISPs DNS address, (NSLOOKUP imap.myisp.com <isp addr="" dns="" server=""> )the request succeeds. so it looks like my router is not forwarding the DNS request. BTW, when this is occurring, all existing connections continue, no dropped connections, no drop outs logged by the modem or router.</isp>
If I configure the ISPs DNS server addresses in my PC Ethernet config, I don't see the issue.
I can't tell if the IPS is causing the issue or my router. To verify, I think I would need to capture the traffic on the internet side of the router. Is this even possible? If so, how? If I put a Managed switch in line and setup a port for Mirroring, would that work? Would the monitoring computer be visible on the ISPs network?
I've called the cable company and they didn't see any issues on their side. I called the router company and they couldn't help. Any ideas on how to narrow this down?
