Go CCIE Go!! - A Cisco Certified Internetwork Expert

Hi Chan,
As the BGP session ISP trying to establish is pointing to a different IP, all those packets are dropped & not processed by your router. I believe no BGP debug commands will interpret those packets.
One way to force the router to “process” those irrelevant BGP packets is to set up an access-list and apply it to the interface in the inbound direction. This will display all incoming packets with source/destination IP info, even if the packets are not addressed to the local router.
See log message below, you notice TCP packets with destination 202.1.1.100.
202.1.1.254(40464) -> 202.1.1.100(179)

R1# access-list 100 permit tcp any any eq bgp log access-list 100 permit tcp any eq bgp any log access-list 100 permit ip any any
interface Serial1/1 ip address 202.1.1.1 255.255.255.0 ip access-group 100 in

R1# *Mar 1 00:15:23.143: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(179) -> 202.1.1.1(33725), 1 packet *Mar 1 00:15:50.027: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(179) -> 202.1.1.1(53753), 1 packet *Mar 1 00:16:20.539: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(179) -> 202.1.1.1(16641), 1 packet *Mar 1 00:16:48.155: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(40464) -> 202.1.1.100(179), 1 packet *Mar 1 00:16:54.459: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(179) -> 202.1.1.1(39740), 1 packet *Mar 1 00:17:22.935: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(179) -> 202.1.1.1(42902), 1 packet *Mar 1 00:17:51.243: %SEC-6-IPACCESSLOGP: list 100 permitted tcp 202.1.1.254(43336) -> 202.1.1.100(179), 1 packet

Cheers, Huan
—–Original Message—– From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of C Chan Sent: Tuesday, 1 April 2008 12:14 PM To: Cisco certification Subject: eBGP peer configured neighbor address discovery
Hi Expert,
Is there any BGP debug command to discover the eBGP peer’s configured neighbor address?
For example, Actual IP address: R1 (202.1.1.1) AS 100 ISP_R (202.1.1.254) (AS 200)
BGP R1 (neighbor 202.1.1.254 remote 200)
*Hidden config from internal network admin* BGP ISP_R (neighbor 202.1.1.100 remote 100)