This attribute indicates the MAC of the device located on this side
of the VC, normally the host device. This address is inserted in the
Destination Address (DA) field of the 802.5 frames sent, typically
to a Token Ring interface. This address is expected in the SA field
of the frames received from the local LAN.
When this attribute is not empty All Route Explorer (ARE) and
Single Route Explorer (SRE) frames received from the local LAN
must have the SA field matching it, otherwise they are discarded.