Router MTU(?) problem

What's going on with a router that's been working for 2 years and
suddenly needs to be reset every day? At first the solution was to
reset the cable modem, and I could always see through the router to the
modem. Then I replaced the modem, but now I have to reset the router.

I'm really curious about what could have changed in the packet traffic.
I can use a sniffer program but I'm not sure what to look for, or if
this would do no good if I can only look at the LAN side.


Here are my notes on the problem:

SYMPTOM: must restart modem every 10 minutes (can usually be done
through the config page)

ACTION: updated router firmware (Linksys BEFSR41 1.45.7, Jul 31 2003)

SYMPTOM: must restart router every day; can't ping router at those times

ACTION: changed router gateway IP from default 192.168.1.1 to
192.168.10.1 (Linksys recommended)

SYMPTOM: back to "must restart modem every 10 minutes"

ACTION: reset all defaults on modem

SYMPTOM: must restart modem even more often

ACTION: replace Motorola modem with Scientific Atlanta

SYMPTOM: must restart router at least every day; can't ping router at
those times

ACTION: insert hub between cable modem and router

SYMPTOM: no change; removed hub

ACTION: progressively decrease MTU, now down to 900

SYMPTOM: must restart router, but a little less often than every day



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