Step 8: Configure router DHCP

Vrodhcp DHCP configuration is required by many administrators. After configuring dhcp in Cisco 3550 and discussing it on the network, according to the "ip helper-address dhcp server ADDRESS", the project finds that the client cannot obtain the ip address from the DHCP server, I recently configured 3550 as a DHCP server relay proxy. I was also confused for a long time. Later, I searched for information online and asked for help from the forum. I finally passed the test in the project, in order to avoid such problems in the project, we need to adjust the configuration process left and right for your reference.

Network Environment: A 3550EMI switch is divided into three VLANs. vlan2 is the network where the server is located, named server, IP address segment is 192.168.2.0, subnet mask: 255.255.255.0, Gateway: 192.168.2.1, the Domain server is a windows 2000 advance server and also serves as a DHCP server. The DNS server has the IP address 192.168.2.10, vlan3 is the network where client 1 is located, the IP address segment is 192.168.3.0, The subnet mask is 255.255.255.0, And the Gateway: 192.168.3.1 is named work01, vlan4 is the network of client 2, work02, IP address segment is 192.168.4.0, subnet mask: 255.255.255.0, Gateway: 192.168.4.1. 3550 Ports 1-8 are allocated to VLAN 2, ports 9-16 are divided into VLAN 3, and ports 17-24 are allocated to VLAN 4.

The vrodhcp DHCP configuration commands and steps are as follows:

Step 1: Create a VLAN

Switch> Vlan Database

Switch (Vlan)> Vlan 2 Name server

Switch (Vlan)> Vlan 3 Name work01

Switch (vlan)> Vlan 4 Name work02

Step 2: enable DHCP relay proxy

/* In the key step, if the following two commands are missing, use "ip helper-address dhcp server ADDRESS" in the VLAN to specify the DHCP server, and the client still cannot obtain the ip address */

Switch> Enable

Switch # Config t

Switch (Config) Service Dhcp

Switch (Config) Ip Dhcp Relay Information Option

Step 3: Set vlan ip addresses

Switch (Config)> Int Vlan 2

Switch (Config-vlan) Ip Address 192.168.2.1 255.255.255.0

Switch (Config-vlan) No Shut

Switch (Config-vlan)> Int Vlan 3

Switch (Config-vlan) Ip Address 192.168.3.1 255.255.255.0

Switch (Config-vlan) No Shut

Switch (Config-vlan)> Int Vlan 4

Switch (Config-vlan) Ip Address 192.168.4.1

255.255.255.0

Switch (Config-vlan) No Shut

Switch (Config-vlan) Exit

/* Note: Because the ports are not configured to VLAN2, 3, 4 at this time, each VLAN will be DOWN. After the ports are allocated to each VLAN, the VLAN will get up */

Step 4: set global port Parameters

Switch (Config) Interface Range Fa 0/1-24

Switch (Config-if-range) Switchport Mode Access

Switch (Config-if-range) Spanning-tree Portfast

Step 5: add the port to VLAN2, 3, 4

/* Add Port 1-8 to VLAN 2 */

Switch (Config) Interface Range Fa 0/1-8

Switch (Config-if-range) Switchport Access Vlan 2

/* Add Port 9-16 to VLAN 3 */

Switch (Config) Interface Range Fa 0/9-16

Switch (Config-if-range) Switchport Access Vlan 3

/* Add Port 17-24 to VLAN 4 */

Switch (Config) Interface Range Fa 0/17-24

Switch (Config-if-range) Switchport Access Vlan 4

Switch (Config-if-range) Exit

/* After this step, each VLAN will get up */

Step 6: Set the IP address of the DHCP server in VLAN3 and 4 in vrodhcp DHCP Configuration

/* No DHCP server address must be specified in VLAN 2 */

Switch (Config) Int Vlan 3

Switch (Config-vlan) Ip Helper-address 192.168.2.10

Switch (Config) Int Vlan 4

Switch (Config-vlan) Ip Helper-address 192.168.2.10

Step 7: Enable Routing

/* After a route is enabled, the hosts in each VLAN can access each other. To further control the access permission, apply the access control list */

Switch (Config) Ip Routing

Step 8: end and save the configuration

Switch (Config-vlan) End

Switch # Copy Run Start