Multi-party research on CISCO router dhcp configuration (1)

In terms of routers, I believe everyone knows CISCO. Do you know about its DHCP server configuration? Here we will introduce in detail the dhcp configuration of the CISCO router. Configure the vrodhcp as a dhcp server to allocate IP addresses to the customer workstation connected to the vro ｡

Solving instances

The following CISCO router dhcp configuration command can be used to configure a vrodhcp as a DHCP server to dynamically assign IP addresses to the DHCP client ｡

 
 

  
  
Router1 # configure terminal
  
  
Enter configuration commands, one per line. End with CNTL/Z.
  
  
Router1 (config) # service dhcp // enable DHCP service
  
  
Router1 (config) # ip dhcp pool 172.25.1.0/24 // define the DHCP address pool
  
  
Router1 (dhcp-config) # network 172.25.1.0 255.255.255.0 // use the network command to define the network address range
  
  
Router1 (dhcp-config) # default-router 172.25.1.1 // defines the gateway address to be allocated
  
  
Router1 (dhcp-config) # exit
  
  
Router1 (config) # ip dhcp excluded-address 172.25.1.1 172.25.1.50 // ip addresses in this range cannot be allocated to clients
  
  
Router1 (config) # ip dhcp excluded-address 172.25.1.200 172.25.1.255 // ip addresses in this range cannot be allocated to clients
  
  
Router1 (config) # end
  
  
Router1 #
 
 

Discussion on dhcp configuration of CISCO Routers

1 The CISCO router dhcp server function is also in ios 12.0 (1) T. this feature makes it unnecessary for us to configure another DHCP server in the center of a dedicated network (or enterprise headquarters), thus reducing network construction costs ｡

2. configuring a dhcp server directly on a vro has its unique advantages over traditional dedicated servers ｡
For example

A. Because the traditional construction method is to set up a dhcp server in the enterprise's headquarters, the branches can obtain the IP address through A router. Therefore, when the dhcp server encounters A problem, the entire enterprise's network will be affected. If the dhcp server function is configured on the routers of each branch, the DHCP server of a branch may be faulty, only the network of the branch can be affected, and other branches can be seen without any impact, thus realizing the localization of the problem ｡

After B implements the DHCP server function on the routers of branches, a large number of DHCP UDP request packets will not be forwarded to the central organization through the wan link. Therefore, compared with the traditional method, it has the advantage of reducing Wan load ｡

C. after implementing the DHCP server function on the routers of different branches, if a wide area network connection fails, the local LAN can still run normally.

D. vrodhcp-based DHCP has high manageability. It is easy to configure through the ios command interface ｡

3. In the preceding configuration example, we use the ip dhcp exclude-address command to specify ip addresses that cannot be allocated. This configuration is often required (or even required, almost all of them; because some addresses are often used for other purposes, for example, we should at least keep the addresses of the routers themselves not allocated to the DHCP client, there are also some network servers, printers, and so on, and we often designate static addresses for them, so this part of the address. We do not allow the routes to be allocated. In the above example, the routes are between 172.25.1.1 and 172.25.1.50, the address between 172.25.1.200 and 172.25.1.255 is retained ｡

4. After the vro dynamically assigns an address to the client, it binds the IP address assigned by the binding and the mac address of the client device, and stores the information in the vro configuration, so that the dhcp service can obtain the same IP address for the next request with the same mac address. The following example shows, use the show ip dhcp binding command to display the ip binding information. Lease expiration indicates the ip address, and the client can take up some time. (Of course, the client can send a dhcp request again before it expires, in fact, the dhcp specification also stipulates that dhcp requests will be issued when the lease period is about half the time. If the lease period fails to be updated, half the time will be saved, he also sends dhcp requests, and so on ｡)

 
 

  
  
Router1#show ip dhcp binding  
  
  
IP address Hardware address Lease expiration Type  
  
  
172.25.1.51 0100.0103.85e9.87 Apr 10 2003 08:55 PM Automatic  
  
  
172.25.1.52 0100.50da.2a5e.a2 Apr 10 2003 09:00 PM Automatic  
  
  
172.25.1.53 0100.0103.ea1b.ed Apr 10 2003 08:58 PM Automatic  
  
  
Router1#