The value of tBgpPeerGroupLocalAddress specifies the local IP address
to be used by peers in this group if not configured for the peer as
advertisement source address.
If set to 0.0.0.0, then use a (non-0.0.0.0) Peer Group Local Address,
or a (non-0.0.0.0) global Local Address. If both are zero then find the
local address by querying the closest interface to the peer address
from the routing table.