Administrator Guide

Layer 3 Routing Commands 1470
configuration for the destination UDP port. If so, the relay agent unicasts the
packet to the configured server IP addresses. Otherwise the packet is not
relayed.
The relay agent only relays packets that meet the following conditions:
• The destination MAC address must be the all-ones broadcast address
(FF:FF:FF:FF:FF:FF).
• The destination IP address must be the IPv4 broadcast address
(255.255.255.255) or a directed broadcast address for the receiving
interface.
• The IP time-to-live (TTL) must be greater than 1.
• The protocol field in the IP header must be UDP (17).
• The destination UDP port must match a configured relay entry or an entry
in Table 7-1.
DHCP relay cannot be independently enabled or disabled globally. Only IP
helper can be enabled or disabled globally. Enabling IP helper enables DHCP
relay.
Commands in this Section
This section explains the following commands:
bootpdhcprelay maxhopcount ip helper-address (global configuration)
bootpdhcprelay minwaittime ip helper-address (interface configuration)
clear ip helper statistics ip helper enable
ip dhcp relay information check show ip helper-address
ip dhcp relay information check-reply show ip dhcp relay
ip dhcp relay information option show ip helper statistics
ip dhcp relay information option-insert
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