This attribute specifies if the domain information should be preserved or
embedded in the frame header. This attribute applies only to backbone
ports and does not affect the access bridge ports. By setting this attribute
to a value of on, domain information could be preserved in frames being
tunnelled across the a backbone, so that this information can be
deciphered at the other end of the backbone tunnel. This preserves the
integrity of the domains thus preventing domain breaches while
tunnelling frames across backbone network.
If the value of this attribute is set to off then domain information is not
preserved in the header of the frames tunnelling through the backbone.
This eliminates the overhead incurred to preserve domain information
across the backbone while tunnelling frames across it.
Preserve domain is relevant when used in conjunction with the following
media: FDDI, ATM MPE, Frame Relay and PPP. It is ignored when
used with other types of media.