Multi-VLAN automatic IP allocation for the floating Bridge of the DHCP

We know that the DHCP service is not able to work in multiple VLANs, so by default, DHCP and VLANs cannot coexist, and the broadcast information emitted by DHCP clients cannot be broadcast across multiple VLANs, and when the client is dispersed across multiple VLANs, Broadcast data failed to send because the client could not be found. How to solve this problem? Configuring a DHCP server for each VLAN is the easiest way to do it, but it's less efficient, so we don't use this approach. In fact, we can use the three-tier switch Relay Agent function to implement this method, because the VLAN is usually in the three-tier switch operation, and the general three-tier switch has DHCP Relay Agent function, so that each VLAN interface on the switch to enable DHCP relay function, In this way, when a client in the VLAN makes a request to connect to the DHCP server, the information is submitted to the interface, and then forwarded to the DHCP server by the interface, when it is not found in the current VLAN. By using this method, you can have the client communicate with the DHCP server as if a pontoon bridge was erected between the client and the DHCP server to restore the sending information between the two. Below, please follow the author together to see how the operation to achieve.

First, configure the switch

To implement the above method, you need to first configure DHCP relay services on the three-tier switch. Because the configuration of each brand switch is basically the same, but the command format will be different, so the following operation may be with your switch, but the configuration of other switches. Here I take the PassPort8600 switch as an example to show you how to configure the DHCP Relay service for layer three switches.

First of all through the three-tier switch to divide the VLAN, and then enter the command "CONF VLAN 1 IP dhcp-relay enable" to start the VLAN DHCP relay function, if you have more than one VLAN, you need to enable them separately. Then is the boot port DHCP relay function, only need to enter the command "conf Ethernet 1/1 IP dhcp-relay enable" Can, of course, we have multiple VLAN end, you need to enter the corresponding command to start its VLAN port relay function.

Finally, configure the interface address, DHCP address, and allowed mode. The command is "Conf IP dhcp-relay create-fwd-path Agent 192.168.1.101 Server 192.168.1.1 mode bootp_dhcp state Enable", where 192.168.1.1 01 is the IP address of the current VLAN interface, 192.168.1.1 is the IP address of the gateway, BOOTP_DHCP indicates that the BOOTP and DHCP two modes are allowed. Also finally, replace the interface address with the continuation of the other VLAN configuration.

Second, configure the DHCP server

Now we just need to find a computer on the network and install the Windows 2000/2003 Server System to act as a DHCP server. After you have prepared your work, you can configure the DHCP server.

Open the DHCP entry from the Administrative Tools in Control Panel, and in the Open window, click the new Scope command under the Action menu, in the Open Operation Wizard window, enter the name of the scope, click Next to fill in the IP address range, set the start IP address, terminate the IP address, subnet mask, and so on (Figure 1 ), continue to click Next to add an excluded range of IP addresses, the IP clients added here will not be available, primarily for use in servers, routers, firewalls, and so on, and will then be prompted to configure lease duration, the default value is 8 days, if the assigned IP address is less, then the value can be set smaller, That is, the frequency of IP address exchange a bit higher, to avoid IP is occupied for a long time, of course, now the intranet IP address is generally rich, then the long time set is not related.

Figure 1

Next, go to the DHCP Options configuration window, that is, whether to set the client's gateway and DNS information, select Yes, I want to configure these options now (Figure 2), then click Next to enter the router (Default gateway) window, enter the address of the gateway in the IP Address field, and click the Add button to join, Then click Next to set the DNS name, also in the IP address of the DNS server to fill in the IP address and click the Add button, you will also be asked to configure the WINS server, generally do not need to change, directly click Next to activate the new scope.

Figure 2

Repeat the procedure above, you can create a corresponding scope for other VLANs in DHCP so that you can configure all of them so that DHCP can be used in harmony with the VLAN, enabling DHCP services to be implemented in multiple VLANs, allowing the network to run faster and more efficiently.