Dell N3200-ON EMC Networking N-Series Switches CLI Reference Guide version 6.6 - Page 1472

Table 6-1. UDP Destination Ports Protocol IEN-116 Name Service DNS NetBIOS Name Server NetBIOS Datagram Server TACACS Server Time Service DHCP Trivial File Transfer Protocol ISAKAMP Mobile IP NTP PIM Auto RP RIP UDP Port Number 42 53 137 138 49 37 67 69 500 434 123 496 520 Certain pre-existing DHCP relay options do not apply to relay of other protocols. The administrator may optionally set a DHCP maximum hop count or minimum wait time. The relay agent relays DHCP packets in both directions. It relays broadcast packets from the client to one or more DHCP servers (as a unicast packet), and relays packets to the client that the DHCP server unicasts back to the relay agent. For other protocols, the relay agent only relays broadcast packets from the client to the server. Packets from the server back to the client are assumed to be unicast directly to the client. Because there is no relay in the return direction for protocols other than DHCP, the relay agent retains the source IP address from the original client packet. The relay agent uses a local IP address as the source IP address of relayed DHCP client packets. When a switch receives a broadcast UDP packet on a routing interface, the relay agent verifies that the interface is configured to relay to the destination UDP port. If so, the relay agent unicasts the packet to the configured server IP addresses. Otherwise, the relay agent verifies that there is a global Layer 3 Routing Commands 1472