Friday, October 07, 2005

Why do both my net interfaces have the same ethernet address?

Subject: 12.1) Why do both my net interfaces have the same ethernet address?

The Ethernet version 2.0 specification (November 1982) states:

The physical address of each station is set by network
management to a unique value associated with the station,
and distinct from the address of any other station on any
Ethernet. The setting of the station's physical address
by network management allows multiple multiple data link
controllers connected to a single station to respond to
the same physical address.

This doesn't normally constitute a problem because each interface will
typically be on a different subnet. If, for some reason, different
ethernet addresses are required on different interfaces (for example, to
attach two interfaces to the same subnet), a new one may be assigned
using the ifconfig command. Alternatively, for all modern Sun hardware,
you can set the "local-mac-address?" eeprom variable to "true", which will
cause each NIC to use a unique MAC address. This is needed for many
failover and trunking configurations.

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