[c-nsp] Sup720-3B Gig port mac address strangeness

Jared Gillis jared at corp.sonic.net
Wed May 27 15:21:22 EDT 2009

Hello all,

I'm working with 2 7606s, each with 1 Sup720-3B, and noticed something strange
when moving the Supervisors between the two chassis. The MAC address assigned to
the gig ports on the Supervisor seems to stick with a chassis, rather than
follow the Supervisor.
For example, I plug Supervisor A into chassis A, and the first gig port on the
supervisor gets assigned MAC address A. Sup B in chassis B gets MAC B likewise.
I then write erase both Supervisors, power down both chassis, and swap the
Supervisors. Now Sup A is in chassis B, and Sup B in chassis A. However, Sup A
in chassis B gets MAC B, and Sup B in chassis A gets MAC A.

This is contrary to how I would expect this to work, as MACs are usually
programmed into the EEPROM on the interface card. This is supported by the Cisco
docs here:

Is this a known "feature" of the 7600/Sup720-3B?

Jared Gillis - jared at corp.sonic.net       Sonic.net, Inc.
Network Operations                        2260 Apollo Way
707.522.1000 (Voice)                      Santa Rosa, CA 95407
707.547.3400 (Support)                    http://www.sonic.net/

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