Why does BGP need to wait for more than 30 seconds before attempting to establish a connection?

When configuring BGP, you need to specify the peer and AS, and specify the outbound interface, multi-hop, timer, and various capabilities. BGP does not support dynamic capability negotiation. Therefore, the modification of these parameters needs to be renegotiated. To prevent frequent interruption of neighbor renegotiation, a proper time parameter is required to ensure that the configuration is complete before the connection is set up.

After the peer is configured, the peer is in the Idle state and rejects any request. Therefore, when the BGP peer is in the Idle state, the request is rejected and the peer is not connected. RFC4271 specifies that a ConnectRetryTimer is required to migrate a BGP state machine from the idle state to the active state.

ConnectRetryTime is a mandatory FSM attribute that stores the initial value for the ConnectRetryTimer. The suggested default value for the ConnectRetryTime is 120 seconds.

By default, the retransmission time of a Huawei device is 32s. You can use the peer timer connect-retry command to modify it.