Dell N1100-ON, Справочное руководство

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Layer 3 Routing Commands
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Table 7-1. UDP Destination Ports
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
Protocol UDP Port Number
IEN-116 Name Service 42
DNS 53
NetBIOS Name Server 137
NetBIOS Datagram Server 138
TACACS Server 49
Time Service 37
DHCP 67
Trivial File Transfer Protocol 69
ISAKAMP 500
Mobile IP 434
NTP 123
PIM Auto RP 496
RIP 520