Verifying DHCP Server Configuration
This topic discusses on various steps involved in verifying the DHCP server configuration.
Verifying DHCP Server Binding and Server Statistics
Purpose
View or clear information about client address bindings and statistics for the extended DHCP local server.
If you delete the DHCP server configuration, DHCP server
bindings might still remain. To ensure that DHCP bindings are removed,
issue the clear dhcp server binding command before you
delete the DHCP server configuration.
Action
To display the address bindings in the client table on the extended DHCP local server:
user@host> show dhcp server binding
To display extended DHCP local server statistics:
user@host> show dhcp server statistics routing-instance customer routing instance
To display the address bindings in the client table on the extended DHCP local server at routing-instance level:
user@host> show dhcp server binding routing-instance customer routing instance
To display extended DHCP local server statistics at routing-instance level:
user@host> show dhcp server statistics routing-instance customer routing instance
To clear the binding state of a DHCP client from the client table on the extended DHCP local server at routing-instance level:
user@host> clear dhcp server binding routing-instance customer routing instance
To clear all extended DHCP local server statistics:
user@host> clear dhcp server statistics
To clear the binding state of a DHCP client from the client table on the extended DHCP local server:
user@host> clear dhcp server binding
To clear all extended DHCP local server statistics at routing-instance level:
user@host> clear dhcp server statistics routing-instance customer routing instance
Viewing DHCP Bindings (Legacy DHCP)
Use the CLI command show system services dhcp
binding to view information about DHCP address bindings, lease
times, and address conflicts.
The following example shows the binding type and lease expiration times for IP addresses configured on a router that supports a DHCP server:
user@host> show system services dhcp binding IP Address Hardware Address Type Lease expires at 192.168.1.2 00:a0:12:00:12:ab static never 192.168.1.3 00:a0:12:00:13:02 dynamic 2004-05-03 13:01:42 PDT
Enter an IP address to show binding for a specific IP address:
user@host> show system services dhcp binding 192.168.1.3 DHCP binding information: IP address 192.168.1.3 Hardware address 00:a0:12:00:12:ab Client identifier 61 63 65 64 2d 30 30 3a 61 30 3a 31 32 3a 30 30 aced-00:a0:12:00 3a 31 33 3a 30 32 Lease information: Type dynamic Obtained at 2004-05-02 13:01:42 PDT Expires at 2004-05-03 13:01:42 PDT
Use the detail option to show detailed
binding information:
user@host> show system services dhcp binding detail DHCP binding information: IP address 192.168.1.3 Hardware address 00:a0:12:00:12:ab Pool 192.168.1.0/24 Interface fe-0/0/0, relayed by 192.168.4.254 Lease information: Type dynamic Obtained at 2004-05-02 13:01:42 PDT Expires at 2004-05-03 13:01:42 PDT DHCP options: name-server foo.mydomain.tld domain-name mydomain.tld option 19 flag off
Viewing DHCP Address Pools (Legacy DHCP)
Use the CLI show system services dhcp pool command to view information about DHCP address pools.
The following example show address pools configured on a DHCP server:
user@ host> show system services dhcp pool Pool name Low address High address Excluded addresses 10.40.1.0/24 10.40.1.1 10.40.1.254 10.40.1.254
Viewing and Clearing DHCP Conflicts (Legacy DHCP)
When a client receives an IP address from the DHCP server, the client performs a series of ARP tests to verify that the IP address is available and no conflicts exist. If the client detects an address conflict, the client notifies the DHCP server about the conflict and may request another IP address from the DHCP server.
The DHCP server keeps a log of all conflicts and
removes addresses with conflicts from the pool. These addresses remain
excluded until you manually clear the conflicts list with the clear system services dhcp conflict command. Use the CLI command show system services dhcp conflict to show conflicts.
user@host> show system services dhcp conflict Detection time Detection method Address 2004-08-03 19:04:00 PDT client 192.168.1.5 2004-08-04 04:23:12 PDT ping 192.168.1.8
Use the clear system services dhcp conflicts command to clear the conflicts list and return IP addresses to the
pool. The following command shows how to clear an address on the server
that has a conflict:
user@host> clear system services dhcp conflict 192.168.1.5
For more information about CLI commands you can use with the DHCP server, see the CLI Explorer.