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Switch (Config)#vlan 2
Switch (Config-Vlan-2)#exit
Switch (Config)#interface Ethernet 1/2
Switch (Config-Erthernet1/2)#switchport access vlan 2
Switch (Config-Erthernet1/2)#exit
Switch (Config)#interface vlan 2
Switch (Config-if-Vlan2)#ip address 10.1.1.1 255.255.255.0
Switch (Config-if-Vlan2)#exit
Switch (Config)#ip forward-protocol udp 67
Switch (Config)#interface vlan 1
Switch (Config-if-Vlan1)#ip help-address 10.1.1.10
Switch (Config-if-Vlan1)#exit
Switch (Config)#ip forward-protocol udp 69
Switch (Config)#interface vlan 1
Switch (Config-if-Vlan1)#ip help-address 10.1.1.20
Switch (Config-if-Vlan1)#exit
Note: DHCP server address and TFTP server address must be configured separately
since their receiving UDP protocols are different. It is recommended to use the
combination of command “ip forward-protocol udp <port>” and ”ip helper-address
<ipaddress>”. “ip help-address” can only be configured for ports on layer 3 and cannot
be configured on layer 2 ports directly.
Usage Guide:
When a DHCP/BootP client is connected to a VLAN1 port of the switch, the client can only
get its address from 10.16.1.0/24 instead of 10.16.2.0/24. This is because the broadcast
packet from the client will be requesting the IP address in the same segment of the VLAN
interface after VLAN interface forwarding, and the VLAN interface IP address is
10.16.1.2/24, therefore the IP address assigned to the client will belong to 10.16.1.0/24.
If the DHCP/BootP client wants to have an address in 10.16.2.0/24, the gateway
forwarding broadcast packets of the client must belong to 10.16.2.0/24. The connectivity
between the client gateway and the switch must be ensured for the client to get an IP
address from the 10.16.2.0/24 address pool.
11.5 DHCP Troubleshooting Help
11.5.1 Monitor and Debug Commands