First, by way of intro, I'm not a networking expert but I've been given the task of figuring out why our network occasionally slows down.
We're a small business with a LAN behind a firewall. Our lan is configured 192.168.0/24 . What's bizarre is that we're seeing a whole bunch of 192.168.254.x, 192.168.2.x, etc etc. Total about 262 odd addresses at last scan. Ping indicates they're outside our LAN, so obviously our ISP isn't particular about routing private IPs.
Questions: Is there any legitimate reason (other than deliberate policy) why we would be able to see these foreign private addresses? Should our firewall be configured to block them? Is there any way that I could quickly test to see if *they* can see *us*? If we can ping them, does this mean we might get leakage from things like their DHCP servers?
And what other things might I check for?