Troubleshooting A Dhcp Relay Configuration - 3Com 7700 Configuration Manual

Troubleshooting a DHCP
Relay Configuration
end in different VLANs. The corresponding interface VLAN of the DHCP Server
Group 1 is configured as 4000, and that of the group 2 is configured as 3001.
[3Com] vlan 4000
[3Com-vlan4000] port Ethernet 1/0/4
[3Com] interface vlan 4000
[3Com-VLAN-Interface4000] ip address 1.99.255.1 255.255.0.0
[3Com] vlan 3001
[3Com-vlan3001] port Ethernet 1/0/5
[3Com] interface vlan 3001
[3Com-VLAN-Interface3001] ip address 1.88.255.1 255.255.0.0
8 Show the configuration of DHCP server groups in User view.
<3Com> display dhcp-server 1
9 Show the DHCP Server Group number corresponding to the VLAN interface in
User view.
<3Com> display dhcp-server interface vlan-interface 2
<3Com> display dhcp-server interface vlan-interface 3
If a user cannot apply for IP address dynamically, perform the following procedure:
1 Use the display dhcp-server groupNo command to check if the IP address of the
corresponding DHCP server has been configured.
2 Use the display vlan and display ip commands to check if the VLAN and the
corresponding interface IP address have been configured.
3 Ping the configured DHCP Server to ensure that the link is connected.
4 Ping the IP address of the VLAN interface of the switch to which the DHCP user is
connected from the DHCP server to make sure that the DHCP server can correctly
find the route of the network segment the user is on. If the ping execution fails,
check if the default gateway of the DHCP server has been configured as the
address of the VLAN interface that it locates on.
5 If there is no problem found in the last two steps, use the display dhcp-server
groupNo command to view what packet has been received. If you only see the
Discover packet and there is no response packet, it means the DHCP Server has
not sent the message to the Ethernet Switch. In this case, check if the DHCP Server
has been configured properly. If the numbers of request and response packets are
normal, enable the debugging dhcp-relay in User view and then use the terminal
debugging command output the debugging information to the console. In this
way, you can view the detailed information of all DHCP packets on the console
during applying for the IP address, thereby conveniently locating the problem.
DHCP Relay 55