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New Member

Loop caused by 7940 when powered off

Just as an information to the AVVID community, please take note of the following:

Customer site with 3Com 4400 Switches. All 7940 phones with external power cube. When one of the phones is powered off by error other reason, the corresponding switch port goes from 100Mbps FD to 10Mbps FD and starts looping (same behaviour as with good old IBM cabling)! The problem only exists with the 7940 phones -7960 are ok! The switch 4400 supports a Auto-MDI feature, with might cause the problem, on older an other switches the problem does not exist at all! Use SPT to resolve the problem and to minimze the risk of loops!

Does somebody know the difference between the 7940 / 7960, I mean beside the known ones ;-) ?




Re: Loop caused by 7940 when powered off

According to this link, these are the only differences between the 7960 and 7940:

The Cisco IP Phone 7960 is a full-featured, multiline phone used primarily by managers and executives. The Cisco 7960 has six programmable buttons for lines or for speed dialing, and it has four interactive soft keys.

The Cisco IP Phone 7940 is for low-to-medium-traffic users who need a minimum of directory numbers. The Cisco 7940 model has two programmable buttons for lines or speed dialing.

Cisco Employee

Re: Loop caused by 7940 when powered off

Just to expand on that, there is no difference between the 7940 and 7960 when it comes to the network interfaces.

New Member

Re: Loop caused by 7940 when powered off

I agree that there is no difference on the network side, if look at the tech papers. The reality shows the real differences and hence, that's what I'm interested in. I tested the behaviour with at least 8 phones from each type and got still the same result.