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Cisco DHCP conflict (client declined) Cisco 2960X

A9191057992
Level 1
Level 1

‎09-12-2017 03:47 AM - edited ‎03-05-2019 09:07 AM

Hi all.

Could you please assist me with one issue

 

Have dhcp conflict on 2960X

Bellow config from switch

 

ip dhcp excluded-address 10.151.0.1 10.151.0.20
ip dhcp excluded-address 10.151.0.100 10.151.0.150
!
ip dhcp pool DATA
network 10.151.0.0 255.255.255.0
dns-server 10.201.0.2 10.151.0.8
default-router 10.151.0.1
lease 3


spanning-tree mode pvst
spanning-tree extend system-id
!

interface Port-channel5
description server
!
interface FastEthernet0
no ip address
!
interface GigabitEthernet1/0/1
description to-ASA
switchport mode trunk
!
interface GigabitEthernet1/0/2
switchport mode access
!
interface GigabitEthernet1/0/3
switchport mode access
!
interface GigabitEthernet1/0/4
switchport mode access
!
interface GigabitEthernet1/0/5
switchport mode access
!
interface GigabitEthernet1/0/6
switchport mode access
!
interface GigabitEthernet1/0/7
switchport mode access
!
interface GigabitEthernet1/0/8
switchport mode access
!
interface GigabitEthernet1/0/9
switchport mode access
!
interface GigabitEthernet1/0/10
switchport mode access
!
interface GigabitEthernet1/0/11
switchport mode access
!
interface GigabitEthernet1/0/12
switchport mode access
!
interface GigabitEthernet1/0/13
switchport mode access
!
interface GigabitEthernet1/0/14
switchport mode access
!
interface GigabitEthernet1/0/15
switchport mode access
!
interface GigabitEthernet1/0/16
switchport mode access
!
interface GigabitEthernet1/0/17
switchport mode access
!
interface GigabitEthernet1/0/18
switchport mode access
!
interface GigabitEthernet1/0/19
switchport mode access
!
interface GigabitEthernet1/0/20
switchport mode access
!
interface GigabitEthernet1/0/21
switchport mode access
!
interface GigabitEthernet1/0/22
switchport mode access
!
interface GigabitEthernet1/0/23
switchport mode access
!
interface GigabitEthernet1/0/24
switchport mode access
!
interface GigabitEthernet1/0/25
switchport mode access
!
interface GigabitEthernet1/0/26
switchport mode access
!
interface GigabitEthernet1/0/27
switchport mode access
!
interface GigabitEthernet1/0/28
switchport mode access
!
interface GigabitEthernet1/0/29
switchport mode access
!
interface GigabitEthernet1/0/30
switchport mode access
!
interface GigabitEthernet1/0/31
switchport mode access
!
interface GigabitEthernet1/0/32
switchport mode access
!
interface GigabitEthernet1/0/33
switchport mode access
!
interface GigabitEthernet1/0/34
switchport mode access
!
interface GigabitEthernet1/0/35
switchport mode access
!
interface GigabitEthernet1/0/36
switchport mode access
!
interface GigabitEthernet1/0/37
switchport mode access
!
interface GigabitEthernet1/0/38
switchport mode access
!
interface GigabitEthernet1/0/39
switchport mode access
!
interface GigabitEthernet1/0/40
switchport mode access
!
interface GigabitEthernet1/0/41
switchport mode access
!
interface GigabitEthernet1/0/42
switchport mode access
!
interface GigabitEthernet1/0/43
switchport mode access
!
interface GigabitEthernet1/0/44
switchport mode access
!
interface GigabitEthernet1/0/45
description WiFi
switchport trunk allowed vlan 1,7
switchport mode trunk
!
interface GigabitEthernet1/0/46
description WiFi
switchport trunk allowed vlan 1,7
switchport mode trunk
!
interface GigabitEthernet1/0/47
description server
channel-group 5 mode on
!
interface GigabitEthernet1/0/48
description server
channel-group 5 mode on
!
interface GigabitEthernet1/0/49
!
interface GigabitEthernet1/0/50
!
interface TenGigabitEthernet1/0/1
!
interface TenGigabitEthernet1/0/2
!
interface Vlan1
description default
ip address 10.151.0.3 255.255.255.0
ip helper-address 10.151.0.3

 

1-DATA vlan (users)

 

7-Vlan-Guest WiFi (dhcp for guest access running on the ASA)

 

The problem with DHCP server for DATA (users dhcp)

Bellow log from Cisco 

Sep 12 10:35:33.126: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client bcc3.4201.06e1 declined 10.151.0.38.
Sep 12 10:35:45.160: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client bcc3.4201.06e1 declined 10.151.0.40.
Sep 12 10:35:54.115: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client 01dc.4a3e.7f3b.00 declined 10.151.0.39.
Sep 12 10:35:57.198: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client bcc3.4201.06e1 declined 10.151.0.41.
Sep 12 10:36:02.927: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client 0154.ee75.a2da.dd declined 10.151.0.60.
Sep 12 10:36:09.229: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client 01dc.4a3e.7f3b.00 declined 10.151.0.42.
Sep 12 10:36:09.239: %DHCPD-4-DECLINE_CONFLICT: DHCP address conflict: client bcc3.4201.06e1 declined 10.151.0.43.

 

I tried to fix it with (no ip dhcp conflict logging) but it was not help

Any sollutions?

Thanks for help

1 person had this problem
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0 Helpful
8 Replies 8

Julio E. Moisa
VIP
VIP

‎09-12-2017 04:43 AM - edited ‎09-12-2017 04:46 AM

Hi

Try executing:

clear ip dhcp conflict address *

And see if you see the problem again. Also you could configure: ip dhcp ping <time in miliseconds>




>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<
0 Helpful

A9191057992
Level 1
Level 1
In response to Julio E. Moisa

‎09-12-2017 04:56 AM

I tried thiese both commands and it was not help.
0 Helpful

Julio E. Moisa
VIP
VIP
In response to A9191057992

‎09-12-2017 05:05 AM

Try

clear ip dhcp binding *




>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<
0 Helpful

A9191057992
Level 1
Level 1
In response to Julio E. Moisa

‎09-12-2017 05:21 AM

after clear ip dhcp binding *
problem still exists
0 Helpful

Julio E. Moisa
VIP
VIP
In response to A9191057992

‎09-12-2017 05:30 AM - edited ‎09-12-2017 05:31 AM

Hi

Try removing the leasing

no lease 3  <-- 3 days. 

and clear again conflict and bindings.




>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<
0 Helpful

A9191057992
Level 1
Level 1
In response to Julio E. Moisa

‎09-12-2017 06:20 AM

done, but still conflict
0 Helpful

Georg Pauwen
VIP
VIP

‎09-13-2017 12:08 PM

Hello,

it looks like the IP address of your Vlan1 interface does not match the one specified in your dhcp pool:

 

interface Vlan1
description default
ip address 10.151.0.3 255.255.255.0
ip helper-address 10.151.0.3

 

ip dhcp pool DATA
network 10.151.0.0 255.255.255.0
dns-server 10.201.0.2 10.151.0.8
default-router 10.151.0.1
lease 3

Change the default router to the Vlan 1 IP address:

 

interface Vlan1
description default
ip address 10.151.0.1 255.255.255.0
ip helper-address 10.151.0.3

 

ip dhcp pool DATA
network 10.151.0.0 255.255.255.0
dns-server 10.201.0.2 10.151.0.8
default-router 10.151.0.1
lease 3

 

Also, what is the purpose of the IP helper address, is there a(nother) DHCP server configured at that address ? Try and remove that altogether:

 

interface Vlan1
description default

ip address 10.151.0.1 255.255.255.0
--> no ip helper-address 10.151.0.3

0 Helpful

paul driver
VIP
VIP

‎09-14-2017 04:10 AM

Hello 

You need to apply a dhcp relay to the switch if the switch itself is providing the allocation.

 

You need to remove it

res
Paul


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul
0 Helpful
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