Edge BGP routing error "PROBLEM 0x0303-25 (0000): A connection attempt has failed"

Products

• VMware NSX

Issue/Introduction

When using BGP on NSX Edge appliance, errors can be observed similar to:
Jan 10 01:14:06 edge-01-0 routing[1007]: PROBLEM 0x0303-25 (0000): A connection attempt has failed

Environment

VMware NSX for vSphere 6.4.x
VMware NSX for vSphere 6.3.x
VMware NSX for vSphere 6.1.x

Cause

This issue occurs when the edge is trying to establish a TCP/IP connection to a defined peer, but it is not able to do so on IP level.

Resolution

Check the routing logging by running the below command on Edge to see which peer has problems:
show log routing reverse
the output could contain similar to the following:
"...
**** PROBLEM 0x0303 - 25 (0000) **** -:-------- F:00000001
sckorig2.c 1366 :at 01:05:11, 10 January 2017 (102688190 ms)
A connection attempt has failed.
Sockets error code = 113
Socket ID = 19
Socket type = 0X00000001
Socket family = 0X00000002
Socket protocol = 0X00000000
Application handle = 0X01DF0000
Stub socket handle = 0X02A50004
Local inet address = 0.0.0.0
Local port = 0
Remote inet address = #.#.#.#
Remote port = 179
..."

Check the ARP table on the Edge and look for the above IP :
show arp

Check if you are able to reach the peer from the Edge with ping :
ping <peer_IP>

If ping fails or ARP table does not show the MAC address of the remote address, check the physical path.