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4. Disable DHCP relay from forwarding DHCP broadcast packet.
Command
Global Mode
ip dhcp relay information policy drop
no ip dhcp relay information policy
drop
14.3.2 DHCP Relay Configuration Command
14.3.2.1
ip forward-protocol udp
Command: ip forward-protocol udp <port>
no ip forward-protocol udp <port>
Function: Sets DHCP relay to forward UPD broadcast packets on the port; the "no ip
forward-protocol udp <port>" command cancels the service.
Default: DHCP relay forwards DHCP broadcast packet to UDP port 67 by default.
Command mode: Global Mode
Usage Guide: The forwarding destination address is set in the "ip helper-address" command and
described later.
Example: Setting TFTP packets to be forwarded to 192.168.1.5.
Switch(Config)#ip forward-protocol udp 69
Switch(Config)#interface vlan 1
Switch(Config-If-Vlan1)#ip helper-address 192.168.1.5
14.3.2.2
ip helper-address
Command: ip helper-address <ip-address>
no ip helper-address <ip-address>
Function: Specifies the destination address for the DHCP relay to forward UDP packets. The "no ip
helper-address <ip-address>" command cancels the setting.
Default: Address for forwarding DHCP broadcast packet is set on DHCP relay by default.
Command mode: Interface Mode
Usage Guide: The DHCP relay forwarding server address corresponds to the port forwarding UDP,
i.e., DHCP relay forwards corresponding UDP packets only to the corresponding
server instead of all UDP packets to all servers. The default setting of DHCP relay is
to forward DHCP packets on UDP port 67 to the DHCP server. When this command
is run after "ip forward-protocol udp <port>" command, the forwarding address
configured by this command receives the UDP packets from <port> instead of
default DHCP packets. If a different set of UDP forwarding protocol and receiving
server address is to be set, the combination of "ip forward-protocol udp <port>"
command and this command should be used for configuration.
EES4710BD 10 Slots L2/L3/L4 Chassis Switch
Explanation
When layer 3 switches are used as DHCP relays,
this command sets the relay forwarding policy to
drop DHCP packets; the "no ip dhcp relay
information policy drop" command allows
DHCP packets forwarding.
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Troubleshooting
