[c-nsp] Ethernet Freezeup

[Ed Ravin]

A few times on this list, people have discussed how a Cisco 1700 series
router can suddenly "freeze up" on its main Ethernet interface.  The
problem as I've observed it hits routers that have a single Ethernet
interface (and no other interfaces in use).  The symptom is that the router
no longer receives traffic on the Ethernet - it still transmits ARP requests
and retries of routing protocol packets, but nothing is received.  Getting to
the console of the router and issuing "clear int faste0" always fixes the
problem.

We've had this problem every 1-2 months on a 1720 in the field, which
was tolerable since the router didn't have that many users on it, but now
it has started happening on one of our core 7206 routers.  We used this
same router in a similar configuration for years in a different location
with no problems, but back then it had multiple interfaces (a DS3 and the
FastEthernet).

The freezeups have happened on various IOS 12.1 versions on the 1720,
and on 12.3.17 on the 7206 (non-VXR, NPE-225).

Any thoughts about what might be going on in the innards of the IOS,
and how to troubleshoot or prevent recurrence?