Why does not a client initiate a TCP connection


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

Other related questions:
Client-initiated VPN
In client-initiated VPN, the LNS authenticates users through PPP authentication (PAP or CHAP). In CLI configurations, this is the PPP authentication configured on the VT interface.

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 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 14849 Listening 0b6d91cc 23 /2 0 Established

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.

Why does the TCP connection fail even if the server and client both initiate a TCP connection
LDP sessions are established based on TCP connections using MD5 authentication. The TCP connection cannot be established, if one end is configured with MD5 authentication while the other end is not, or the MD5 passwords on the two ends are different. If MD5 cipher text authentication is proprietary on other vendors' devices, Huawei devices cannot set up a TCP connection with these devices.

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