Trouble shooting: Cisco router DHCP No option 125

Posted by Blog - uTIcARdI on November 13, 2013

Topology:

Topo
Topo

Configure DHCP on Cisco router 2811 to assign a static IP to the italkBB: Cisco SPA 1202.

  1. start DHCP service by command:

    service dhcp
    
  2. debug on Cisco router to check DHCP request by the commands:

    debug ip dhcp server packet
    terminal monitor
    

    Debug info :

    DHCPD: DHCPREQUEST received from client 0100.1c23.3541.98
    
  3. configure DHCP

    ip dhcp pool ItalkBB
        host 10.0.0.127 255.255.255.0 //no mask configured, IP’s class mask assigned
        client-identifier 0100.1c23.3541
        default-router 10.10.10.99
    

    But italkBB can’t get IP from Cisco router 2811, and the error msg in debug info is:

    DHCPD: client’s VPN is .
    DHCPD: No option 125
    

    Checked DHCPREQUEST on Cisco Router in debugging mode:

    DHCPD: DHCPREQUEST received from client 0100.1c23.3541.98
    
  4. change client-identifier by command:

    client-identifier  0100.1c23.3541.98
    

ItalkBB works.

Note: from my understanding, the MAC of the iTalkBB should be ‘0100.1c23.3541’, in fact, the suffix: ‘.98’ is required as a part of the identifier.

The basic config file for configuring DHCP SERVER on Cisco router

service dhcp
no ip dhcp conflict logging
!
ip dhcp pool 1
 network 11.0.0.0 255.0.0.0
 default-router 11.0.0.1
!
interface GigabitEthernet0/1
 ip address 11.0.0.1 255.0.0.0

A case from blog : Embedded System Testing Blog

“No option 125” error from Cisco DHCP server Problem : “No option 125” error was continuously repeating and DHCP Server on Cisco was not offering any IP address to the clients.

Jul 24 05:36:21.147: DHCPD: No option 125
Jul 24 05:36:21.147: DHCPD: DHCPDISCOVER received from client 001e.e5dc.ae.c0 on interface GigabitEthernet0/1.
Jul 24 05:36:30.707: DHCPD: client’s VPN is .
Jul 24 05:36:30.707: DHCPD: No option 125

Solution: After some debugging, came to know that the problem is with the subnet configured on the Gigabit ethernet. For DHCP Server to offer the ip address at least one interface should be in the same network as the pool is defined. Once the subnet is properly configured, the Server started replying.


Trouble shooting: Cisco router DHCP No option 125


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