Q: How do I control what prefixes I accept into my routing table from a BGP neighbor?

A:

Assume my AS is 12345, and I only want to accept 1.2.3.0/23 from my neighbor at 1.4.5.6.

router bgp 12345
neighbor 1.4.5.6 prefix-list PL0002 in
...
ip prefix-list PL0002 seq 5 permit 1.2.3.0/23