[ILUG] wifi woes -- host suddenly goes all Destination Unreachable

[Justin Mason]

OK, here's an odd networking question.  I have three linux hosts...

  - radish: laptop running Ubuntu Hoary, builtin 802.11a/b with madwifi
    drivers, or wired 100Mbps ethernet, 2.6.10 kernel
  - jalapeno: chunky desktop running old Fedora Core, 100Mbps ethernet,
    2.4.23 kernel
  - potato: MythTV box running KnoppMyth r5a12 with a USB zd1201 802.11b
    dongle, 2.6.7 kernel (in an old Sun tape drive case! pics here:
    http://taint.org/wk/FreevoPics )
  - POS Netgear el-cheapo combined 802.11a/b base station and 4-port
    10/100Mbps ethernet switch
  - old Linksys 802.11b base station, hooked up to the switch via
    10Mbps ethernet, for a little extra coverage

all are running 2.6.x kernels, where x >= 7.

The zd1201 dongle is a bit unreliable -- it regularly stops routing
packets silently, and has to be plugged out and in again.  (this is a pity,
as NFS from potato would be nice if it was reliable, and I don't want to
run ethernet cables if it can be avoided.  but hey.)

Anyway, the main problem is this: frequently, I attempt to connect to
potato from radish and it appears to be down -- I get ICMP Destination
Host Unreachable messages from ping.  This happens whether radish is on
the wired network or the wifi one.

However, if I ssh over to jalapeno, I can ping and connect to potato no
problem from there.

Anyone got any ideas on what I should check?  And where?

--j.