10.0.0RTA#ROUTER BGP 100NEIGHBOR 150.10.20.2 REMOTE-AS 300NETWORK...

RTA#

router bgp 100

neighbor 150.10.20.2 remote-as 300

network 150.10.0.0

RTB#

router bgp 200

neighbor 160.10.20.2 remote-as 300

network 160.10.0.0

RTC#

router bgp 300

neighbor 150.10.20.1 remote-as 100

neighbor 160.10.20.1 remote-as 200

network 170.10.00

Note that you do not need network 150.10.0.0 or network 160.10.0.0 in

RTC unless you want RTC to also generate these networks on top of passing

them on as they come in from AS100 and AS200. Again the difference is

that the network command will add an extra advertisement for these same

networks indicating that AS300 is also an origin for these routes.

An important point to remember is that BGP will not accept updates that

have originated from its own AS. This is to insure a loop free

interdomain topology.

For example, assume AS200 above had a direct BGP connection into AS100.

RTA will generate a route 150.10.0.0 and will send it to AS300, then RTC

will pass this route to AS200 with the origin kept as AS100, RTB will

pass 150.10.0.0 to AS100 with origin still AS100. RTA will notice that

the update has originated from its own AS and will ignore it.