HP 6125G HP 6125G & 6125G/XG Blade Switches High Availability Configur - Page 41

Packet type LinkDown packet Processing procedure If not, performs no processing. Checks whether the local port operates in Enhanced mode If yes and the local port is not in Disable state, sets the state of the corresponding neighbor to unidirectional, and then checks the state of other neighbors. If all the neighbors are unidirectional, transitions the local port to the Disable state. If the state of some neighbors is unknown, waits until the state of these neighbors is determined. If bidirectional neighbors are present, removes all unidirectional neighbors. 3. If no echo packet is received from the neighbor, DLDP performs the following processing. Table 16 DLDP process when no echo packet is received from the neighbor No echo packet received from the neighbor Processing procedure In normal mode, no echo packet is received when the Echo timer expires. In enhanced mode, no echo packet is received when the Echo timer expires. DLDP sets the state of the corresponding neighbor to unidirectional, and then checks the state of other neighbors: • If all the neighbors are unidirectional, removes all the neighbors, transitions to the Disable state, outputs log and tracking information, and sends Disable packets. In addition, depending on the user-defined DLDP down mode, shuts down the local port or prompts users to shut down the port. • If the state of some neighbors is unknown, waits until the state of these neighbors is determined. • If bidirectional neighbors are present, removes all unidirectional neighbors. Link auto-recovery mechanism If the port shutdown mode upon detection of a unidirectional link is set to auto, DLDP automatically sets the state of the port, where a unidirectional link is detected, to DLDP down. A DLDP down port cannot forward data traffic or send/receive any PDUs except DLDPDUs. On a DLDP down port, DLDP monitors the unidirectional link. Once DLDP finds out that the state of the link has restored to bidirectional, it brings up the port. The specific process is: The DLDP down port sends out a RecoverProbe packet, which carries only information about the local port, every two seconds. Upon receiving the RecoverProbe packet, the remote end returns a RecoverEcho packet. Upon receiving the RecoverEcho packet, the local port checks whether neighbor information in the RecoverEcho packet is the same as the local port information. If they are the same, the link between the local port and the neighbor is considered to have been restored to a bidirectional link, and the port will transit from Disable state to Active state and re-establish relationship with the neighbor. Only DLDP down ports can send and process Recover packets, including RecoverProbe packets and RecoverEcho packets. If related ports are manually shut down with the shutdown command, the auto-recovery mechanism will not take effect. DLDP neighbor state A DLDP neighbor can be in one of the three states described in Table 17. 34