BGP-4 Aggregator Router list. This octet string contains
the IP addresses of one or more BGP routers. If a router
address appears in this list, this filter applies to BGP
advertisements that contain the address in their AGGREGATOR
path attribute.
If non-null, The octet string contains one or more 4-octet
IP addresses. If null, this filter applies to BGP
advertisements with any router address in the AGGREGATOR
path attribute.