Support for ICMP forwarding and messaging

Load Balancer supports forwarding and processing ICMP messages to improve the robustness of connection protocols and permit Load Balancer to receive ICMP fragmentation messages.

Load Balancer forwards an ICMP message based on the following guidelines:
  • For ICMP packets that contain headers with IP and TCP/UDP fragments, Load Balancer forwards to packets to the correct back-end server.
  • For ICMP packets that do not contain TCP/UDP fragments, Load Balancer forwards the packets in a round-robin manner.
  • For ICMP messages that are for an IPGRE or an IPIP message that Load Balancer generated, Load Balancer limits the outbound size for future packets.
  • If Load Balancer forwards an IP packet, but the time to live (TTL) for the packet becomes zero when the TTL is decremented, Load Balancer sends an ICMP Time Exceeded message to the client.
  • When Load Balancer cannot forward a packet, it generates an ICMP message and sends the appropriate message back to the client:
    • The outbound interface MTU is too small, or you need to use encapsulation.
    • Load Balancer cleaned up a connection record. For example, the cluster and port designation match, but the server is not present.