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

Phil Mayers p.mayers at imperial.ac.uk
Thu May 28 13:17:52 EDT 2009

On Wed, May 27, 2009 at 08:21:22PM +0100, Jared Gillis wrote:
>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?

IIRC SVIs use the chassis mac address, and routed ports use the phy MAC 
address. L2 PDUs (STP, CDP, LLDP) always use the phy mac.

>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/
>cisco-nsp mailing list  cisco-nsp at puck.nether.net
>archive at http://puck.nether.net/pipermail/cisco-nsp/

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