How to determine the interface address used to establish a TCP connection

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By default, the LSR ID is used to establish a TCP connection. If the mpls ldp transport-address command is configured in the interface view, the address of the specified interface is used to establish a TCP connection.

Other related questions:
How are the server and client determined for establishing a TCP connection
Check the transport addresses used to establish a TCP connection. The larger address is the active end that initiates the TCP connection. It is the client of the TCP connection. The smaller address is the server of the TCP connection.

How to check the transport addresses used to establish a TCP connection
To check the transport addresses used to establish a TCP connection, run the display mpls ldp session verbose command.

How to check the LDP TCP connections and determine whether TCP connections are normal
The port number for LDP-dedicated TCP connections is 646. Run the display tcp status command. All connections with port number of 646 are LDP TCP connections. In most cases, the server has a Listening port and one or more Established connections. The local port number is 646, and the remote port number is a randomly allocated five-digit numeral. The command output is displayed as follows: display tcp status TCPCB Tid/Soid Local Add:port Foreign Add:port VPNID State 0d3bda5c 32 /1 0.0.0.0:23 0.0.0.0:0 14849 Listening 0b6d91cc 23 /2 2.2.2.2:646 1.1.1.1:53585 0 Established

How do I check the TCP connection established using LDP
LDP uses TCP port 646. Run the display tcp status command. If port 646 is used, TCP connections are established using LDP.

Why does a TCP connection fail to be established even if ping succeeds
To establish a TCP connection, the server must have a Listening port and the client must initiate a TCP connection. Run the display tcp status command to check whether a Listening port is configured on the server and the client initiates a TCP connection.

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