DHCP Relay Implementation
Configuring DHCP Relay
page 21-10
OmniSwitch AOS Release 7 Network Configuration Guide
June 2013
To delete an IP address, use the
no
form of the
command. The IP address specified with
this syntax is deleted. If an IP address is not specified with this syntax, then
all
IP helper addresses are
deleted. The following command deletes a helper address for IP address 125.255.17.11:
-> no ip helper address 125.255.17.11
The following command deletes all IP helper addresses:
-> no ip helper address
Configuring BOOTP/DHCP Relay Parameters
Once the IP address of the DHCP server(s) is defined and the DHCP Relay is configured for either Global
DHCP request or Per-VLAN DHCP request, you can set the following optional parameter values to
configure BOOTP relay.
•
The forward delay time.
•
The hop count.
•
The relay forwarding option.
The only parameter that is required for DHCP relay is the IP address to the DHCP server or to the next hop
to the DHCP server. The default values can be accepted for forward delay, hop count, and relay
forwarding option.
Alternately the relay function can be provided by an external router connected to the switch; in this case,
the relay must be configured on the external router.
Setting the Forward Delay
Forward Delay is a time period that gives the local server a chance to respond to a client before the relay
forwards it further out in the network.
The UDP packet sent by the client contains the elapsed boot time value. This is the amount of time,
measured in seconds, since the client last booted. DHCP Relay does not process the packet unless the
elapsed boot time value of the client is equal to or greater than the configured value of the forward delay
time. If a packet contains an elapsed boot time value that is less than the specified forward delay time
value, DHCP Relay discards the packet.
The forward delay time value applies to all defined IP helper addresses. The following command sets the
forward delay value of 10 seconds:
-> ip helper forward-delay 10