Hi Tim, I'll just ask lots of questions in the hope it strikes lucky.
> I have a puzzling issue here, in that I can't see a laptop on my > network from my own computer (normally I can ssh into the laptop just > fine). Both are connected via Wifi. The laptop has a static IP. So both Computer and Laptop are *only* connected by Wi-fi. Computer's IP address is from the router's DHCP server. The Laptop's IP address is static. Is that last one done by having the DHCP server always dish out the same IP address for Laptop's MAC address, or the Laptop has it configured directly? If the latter, does the DHCP server know to steer clear of the static addresses when allocating dynamically? Can Laptop see Computer, e.g. ping(1), when Computer can't see Laptop? All devices are on the same IP network, including the network mask? > However, I can ssh into a third computer on the network How is Third connected? Also Wi-fi only? Static or dynamic IP address? > and from there can ping (and ssh into) the laptop. When Computer SSH's into Third, does w(1) show you've come from the Computer IP address you expect? Does `arp' show Computer's MAC address or that of an access point? Can Laptop SSH into Third? Ditto above WRT w(1). > arp lists the laptop HWaddess as incomplete. There's also ip-neighbour(8) that gives `ip neigh' to show the table, and allows an entry to be added. When it's not working, you could try explicitly adding an ARP table entry to Computer for Laptop and see if that makes it work. > I am periodically seeing issues of this kind, and would like to try to > figure out what's going on. `sudo -i tcpdump -i ens35 -n arp', substituting the appropriate network interface, lets one watch ARP traffic and can be run on multiple machines at once. Cheers, Ralph. -- Next meeting: BEC, Bournemouth, Tuesday, 2019-02-05 20:00 Check to whom you are replying Meetings, mailing list, IRC, ... http://dorset.lug.org.uk/ New thread, don't hijack: mailto:dorset@mailman.lug.org.uk
