Why does not a server establish a Listening port

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The prerequisite for a server to establish a Listening port is: The server receives a Hello message from the peer end and finds itself the destination server based on the transport address carried in the Hello message. If the server does not establish a Listening port, check the Hello message receiving and transport address in the received Hello message.

Other related questions:
Why does an S series switch as a server fail to negotiate a Listening port with another device
For S series switches (except the S1700), the reason why a server fails to negotiate a Listening port with another device is as follows: The prerequisite for a server to negotiate a Listening port with another device is that the server receives a Hello message from the peer and finds that it is the destination server based on the transport address carried in the Hello message. Therefore, if the server does not negotiate a Listening port with another device, check whether the Hello message is received and check the transport address in the received Hello message.

Problem and solution when BGP peer cannot be established
The BGP peer establishment on the firewall needs to use port 179 to establish TCP sessions and requires that OPEN messages be properly exchanged. Perform as follows to rectify the issue: 1. Check whether the AS number and IP address among peers are correct by using the display bgp peer command. 2. Check whether the router IDs configured on both BGP peers are conflicting by using the display bgp peer command. 3. If the loopback interface is used, check whether the peer connect-interface command is configured to specify the loopback interface as the source interface for sending BGP packets. 4. If EBGP neighbors are not directly connected to the physical layer, check whether the peer ebgp-max-hop command is configured. 5. Check whether there are available routes to the peer in the routing table. 6. Check whether there are reachable routes to the specified connect-interface by using the ping -a source-ip-address host-address command. 7. Check whether the ACL that is used to disable TCP port 179 is configured.

Method used to identify listening ports on the host
Method used to identify listening ports on the host: For each client, ISM subscribes to the reported information on the device. In that case, a port is listened. As multiple ISMs on a PC can be listened to manage the device, ports listened by ISM are within a certain range. The scope of listening port of ISMV1R3 is 8000 to 8090, 7890, and 8901. In the Windows command line, enter netstat -a to check whether ports within the range are listened. (In the following example, ISM uses port 8011) You can check on the device the file of ports that are reported: /ISM/repository/root#cimv2/instances/CIM_IndicationSubscription.idx In the file, 1 is invalid and the content starting with 0 is valid.

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