IP conflicts error

[eash]

Dear All,

I have configured DHCP on L3 switch for the  VLAN on my LAN. When the users connect an IP conflict error appears and then users are able to obtain the IP address and connect.

Request your kindly suggestion to stop this error from appearing.

My DHCP configuration is as below 

ip dhcp excluded-address 192.168.210.1 192.168.210.31
ip dhcp excluded-address 192.168.210.160 192.168.210.254

!
ip dhcp pool DHCP5
   network 192.168.210.0 255.255.255.0
   default-router 192.168.210.200 
   dns-server 192.168.1.200
  !

Regards,

Easwar

[Walter Astori]

Can you execute the below command :

show ip dhcp binding

and try to change default router in a ip address that isn't in dhpch excluded address range

[eash]

Yes the defualt route is another IP address which not in the excluded range.

Just to repharse the problem,

The DHCP is configured in the L3 switch and the config 

 whenever the user connect user PC connects to LAN before the PC obtains the IP address from the DHCP configured on L3 switch a IP conflict error appears, after which the PC is able to obtain the IP address and connect.

Request your kindly suggestion to stop this error from appearing.

Easwar

[Walter Astori]

Try to configure the lease with a time less that one day

[eash]

Thanks to everyone for the reply,

Yes marcel you are right, IP conflict is reported by your client (PC)

I have changed the config as suggested by the status is the same. In fact it is worse some PC are not able to obtain IP address from the DHCP.

The config as below,

p dhcp excluded-address 192.168.210.1 192.168.210.31
ip dhcp excluded-address 192.168.210.160 192.168.210.254

!

ip dhcp pool DHCP5

   network 192.168.210.0 255.255.255.0

   default-router 192.168.210.200 

   dns-server 192.168.1.200

   lease 48

  !

!
interface Vlan2100
 description Office (FF) & (GF)
 ip address 192.168.210.200 255.255.255.0

 no ip proxy-arp
!

Looking forward to you suggestion..

Eash

[eash]

Dear All,

Just to provide more information, the connectivity diagram is as below,

                             connectivity diagram is as below,

                                                           L3 Switch

                                                            |

                                                            |

                                                           L2 Switch

                                                           |

                                                           |

                                                         PC 

When I checked the sh ip dhcp conflict on the L3 switch, the output as below

Switch-1>sh ip dhcp conflict
IP address        Detection method   Detection time          VRF
192.168.210.32    Ping               Mar 01 1993 12:02 AM

192.168.210.33    Ping               Mar 01 1993 12:02 AM

192.168.210.41    Ping               Mar 01 1993 12:04 AM

192.168.210.42    Ping               Mar 01 1993 12:04 AM

192.168.210.58    Gratuitous ARP

[eash]

Dear All,

When I checked the sh ip dhcp conflict on the L3 switch today the count of conflicted IP is increasing.

[Marcel Zehnder]

The IP conflict is reported by your client (PC) and not by the router, correct?

If yes, try to disable proxy-arp on your dhcp-VLAN:

int vlan <xyz>

 no ip proxy-arp

HTH

Marcel
 

[devils_advocate]

I would second what Marcel has put here, my first thought was Proxy Arp.

Try disabling and see if it resolves the issue.