BGP | %BGP-4-MSGDUMP: unsupported or mal-formatted message received

Networking
1

While i am doing I-bgp config i am getting loads of BGP-3-NOTIFICATION | BGP-5-NBR_RESET | BGP-5-ADJCHANGE | BGP_SESSION-5-ADJCHANGE:

Error Msg

*May 7 08:03:40.175: %SYS-5-CONFIG_I: Configured from console by console
*May 7 08:03:40.787: %LINK-3-UPDOWN: Interface FastEthernet2/0, changed state to up
*May 7 08:03:41.787: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet2/0, changed state to up
*May 7 08:03:49.427: %BGP-3-NOTIFICATION: sent to neighbor 192.168.23.2 passive 2/3 (BGP identifier wrong) 4 bytes 02020202
*May 7 08:03:49.431: %BGP-4-MSGDUMP: unsupported or mal-formatted message received from 192.168.23.2:
FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 0039 0104 0002 00B4 0202 0202 1C02 0601
0400 0100 0102 0280 0002 0202 0002 0246 0002 0641 0400 0000 02
*May 7 08:03:51.951: %BGP-3-NOTIFICATION: received from neighbor 192.168.23.2 active 2/3 (BGP identifier wrong) 4 bytes 02020202
*May 7 08:03:51.951: %BGP-5-NBR_RESET: Neighbor 192.168.23.2 active reset (BGP Notification received)
*May 7 08:03:51.951: %BGP-5-ADJCHANGE: neighbor 192.168.23.2 active Down BGP Notification received
*May 7 08:03:51.951: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.23.2 IPv4 Unicast topology base removed from session BGP Notification received
*May 7 08:03:53.963: %BGP-5-NBR_RESET: Neighbor 192.168.23.2 passive reset (BGP Notification sent)
*May 7 08:03:53.963: %BGP-5-ADJCHANGE: neighbor 192.168.23.2 passive Down BGP Notification sent
*May 7 08:03:55.631: %BGP-3-NOTIFICATION: sent to neighbor 192.168.23.2 passive 2/3 (BGP identifier wrong) 4 bytes 02020202
*May 7 08:03:55.631: %BGP-4-MSGDUMP: unsupported or mal-formatted message received from 192.168.23.2:

BLR Config
interface Loopback0
ip address 2.2.2.2 255.255.255.0
interface FastEthernet1/0
ip address 192.168.13.3 255.255.255.0
duplex full
!
interface FastEthernet2/0 - (Made this shut to observe the logs)
ip address 192.168.23.3 255.255.255.0
shutdown
duplex full

router bgp 2
bgp log-neighbor-changes
network 2.0.0.0 mask 255.255.255.0
neighbor 192.168.13.1 remote-as 1
neighbor 192.168.23.2 remote-as 2

Hyderabad Config

interface Loopback0
ip address 2.2.2.2 255.255.255.0
!
interface FastEthernet0/0
ip address 192.168.12.2 255.255.255.0
duplex full

!
interface FastEthernet2/0
ip address 192.168.23.2 255.255.255.0
duplex full

!
router bgp 2
bgp log-neighbor-changes
network 2.0.0.0 mask 255.255.255.0
neighbor 192.168.12.1 remote-as 1
neighbor 192.168.23.3 remote-as 2

Could someone please suggest what did i do wrong
image

2

OK,
After spending some time and looking to the config multiple times with and with the help of internet i came across to know that above error comes when both the BGP router ID conflicts.

Root Cause
This happened in my case when i tried creating loopback on HYD and BNG** router using notepad and then advertised the same loop back from both the router under BGP.
While BGP was was trying to establish neighborship between HYD and BNG router they realized the same router ID on both router hence were not building neighbor ship.

Resolution

I then changed **

BGP Config
BGP Config1654×416 213 KB

image
TCP Reset
TCP Reset777×832 49.8 KB

BNG** router id to its Physical Interface which resolved the issue and the Neighbor came up with no error.

Just thought of sharing this experience which i felt was really informative.

Feel free to add anything which anyone else has observed with my shared Topology.

3

Please read this article.

4

Yes, i have applied the fix already and shared what steps were taken to resolve.

Issue Stands resolved :slight_smile:

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