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58 CHAPTER 4: NETWORK PROTOCOL OPERATION
6 Configure the corresponding interface and gateway address of VLAN3.
[SW8800]vlan 3
[SW8800-vlan3]port GigabitEthernet 1/1/3
[SW8800]interface vlan 3
[SW8800-VLAN-Interface3]ip address 21.2.2.1 255.255.0.0
7 It is necessary to configure a VLAN for the servers. The corresponding interface
VLAN of the DHCP server group 1 is configured as 4000, and that of the group 2
is configured as 3001.
[SW8800]vlan 4000
[SW8800-vlan4000]port GigabitEthernet 1/1/4
[SW8800]interface vlan 4000
[SW8800-VLAN-Interface4000]ip address 1.99.255.1 255.255.0.0
[SW8800]vlan 3001
[SW8800-vlan3001]port GigabitEthernet 1/1/5
[SW8800]interface vlan 3001
[SW8800-VLAN-Interface3001]ip address 1.88.255.1 255.255.0.0
In this example, clients on VLAN2 will receive IP addresses from the servers in
DHCP server group 1 (VLAN 4000). Clients on VLAN3 will receive IP addresses
from the servers in DHCP server group 2 (VLAN 3001).
8 Show the configuration of DHCP server groups in User view.
<SW8800>display dhcp-server 1
9 Show the DHCP Server Group number corresponding to the VLAN interface in
User view.
<SW8800>display dhcp-server interface vlan-interface 2
<SW8800>display dhcp-server interface vlan-interface 3
Troubleshooting a DHCP
Relay Configuration
Perform the following procedure if a user cannot apply for an IP address
dynamically:
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 where 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 no problems are found in the last two steps, use the display dhcp-server
groupNo command to view the packet that 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 Switch 8800. 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 to output the debugging information to the console. In
this way, you can view the detailed information of all DHCP packets on the
console while applying for the IP address, thereby, conveniently locating the
problem.