5. Troubleshooting

Q: I get kicked offline about once every 4 days, for no apparent reason, and get the following error, or something similar, in the kernel log:

Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110 Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110 Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110 Feb 20 10:05:12 K7 kernel: CDCEther.c: no repsonse in BULK IN Feb 20 10:05:12 K7 kernel: CDCEther.c: rx status -110

A: There are a number of reasons this may be happening, and future updates to the CDCEther driver may solve some of them. At least one user on the Linux-USB-user mailing list noticed that on at least one occasion data sent to the modem from upstream by the cable provider has triggered it. Also, the modem itself is very sensitive to power interruptions and can lose the connection if this occurs. The fix is to run ifdown ethX, where ethX is the Ethernet interface (eth0, eth1 etc.) to clear out any remaining settings that are hung, then remove the module with rmmod CDCEther, reinsert the CDCEther module and then ifup ethX . A reboot may be necessary if this doesn't fix the problem. If none of these work you probably have a real service interruption.

Q: I get the following messages on boot-up; are they errors?

Can't use SetEthernetMulticastFilters request Mar 2 11:00:52 K7 kernel: CDCEther.c: Ethernet information found at device configuration. Trying to use it anyway. Mar 2 11:00:52 K7 kernel: CDCEther.c: Imperfect filtering support - need sw hashing

A: No. The multicast message is pertaining to Multicast support in the kernel, which is optional and not necessary for the proper functioning of this modem. The message about 'Ethernet Information' is a design bug in the modem and can be ignored. As for the 'Imperfect filtering support, to quote Brad Hards:

"This is a bit difficult to explain - I assume that you know what multicasting is - when you join a multicast group, this can be handled by the networking device so that other multicast traffic doesn't cause interrupts. That is called 'perfect filtering.' However sometimes the number of multicast addresses exceeds the number of filters that you have. This leads to 'imperfect filtering,' which can cut down the number of interrupts, but you still need to do some work in the networking stack. Then you get to the typical cable modem implementation, and there is not filtering at all. Every multicast packet goes to the host to be filtered. This doesn't normally matter though, because the cable modem is a point to point link."