internal dhcp with anchor and foreign

Answered Question
Aug 9th, 2012

Greetings,

trying to get dhcp going for guest clients.

I can see dhcp requests coming through and getting dropped at the foreign controller.

*DHCP Socket Task: Aug 10 16:19:54.075: 58:94:6b:1d:xx:yy DHCP received op BOOTREQUEST (1) (len 308,vlan 0, port 13, encap 0xec03)

*DHCP Socket Task: Aug 10 16:19:54.075: 58:94:6b:1d:xx:yy DHCP dropping packet

Could someone tell me;

1. why would the DHCP requests processed by the foreign controller instead of the anchor ?

2. do i need to configure dhcp server under the guest WLAN interface on foreign?

I thought all L3 and security stuff is forwarded over eoip to anchor and therefore no need to configure the DHCP server under foreign.

I'm trying to utilise the internal DHCP server (firmware 7.0.220) but so far its not going well.

Thanks,

silva

I have this problem too.
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Correct Answer by Steve Rodriguez about 1 year 8 months ago

MPING and EPING test conectivit between the WLC only. 

If you are seeing the DHCP request on the internl WLC, then the client most likely is not being pushed to the anchor.  This happens if the WLAN configs aren't the same on both.

you can run the below concurrently, and see if the WLC is saying that the WLAN doesn't exist

debug client < client mac address >

debug mobility handoff enable

HTH,
Steve

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Scott_OBrien Fri, 08/10/2012 - 00:30

I have Never trusted the interal DHCP server on controllers and allways recomend not using it ( version 7.3 wlc code is rumored to remove the feature)

are the interfaces set up the exact same way on both?

is it working for any other interface? or is it just the guest interface having hte issue?

jaysilva6 Fri, 08/10/2012 - 01:22

Hi Scott,

Thanks for the reply. I also have seen internal DHCP working different on Cisco platforms ie 3560 and 1840  :-)

I will try using setting upa scope on the switch.

Well interfaces are not setup the same way.I have an un-routable  interface on the foreign and the proper guest dmz interface on the anchor controller.WLAN configs are identical.

I changed the guest interface to management on the foreign and the results were the same.I rebooted the controllers(as i;m ina test setup) but nothing changed.

thanks,

Silva

fbarboza Fri, 08/10/2012 - 07:57

Hi Silva,

Make sure that the WLAN is configured on the WLCs exactley the same way, the only difference would be the interface the WLAN is linked to.

Make sure that the data path and control path between the anchor and foreign WLC is up and also since the WLC is the DHCP server that you have checked the option of enable DHCP proxy on both.

jaysilva6 Fri, 08/10/2012 - 13:10

Hi fbarboza,

I think the anchoring is working i can see both control and data are in up/up state.further  I can do mping and epings sucessfully.proxy is enabled on both controllers.

Thanks,

Silva

Correct Answer
Steve Rodriguez Fri, 08/10/2012 - 13:16

MPING and EPING test conectivit between the WLC only. 

If you are seeing the DHCP request on the internl WLC, then the client most likely is not being pushed to the anchor.  This happens if the WLAN configs aren't the same on both.

you can run the below concurrently, and see if the WLC is saying that the WLAN doesn't exist

debug client < client mac address >

debug mobility handoff enable

HTH,
Steve

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jaysilva6 Fri, 08/10/2012 - 18:19

Hi Stephen,

Thanks for the reply.

What you suggested make sense.I will recreate the WLANs and then  run the debugs  when I'm bact at work next week.Will keep you posted.

Best regards,

S

jaysilva6 Sun, 08/12/2012 - 17:18

Hi All,

Steve you got me thinking and thanks to the debugs you provided, I  managed to fix the issue.The problem was caused by local EoIP tunnel that was configured on the foreign  and thus traffic was not getting forwarded.Strange thing I can't remember configuring that as it was not required.Anyway after I removed it, all worked as expected. I'm using internal DHCP and so far it is is working fine as well.

With the ACLs, for guest WLAN, do we neded to configure for both foreign and anchors so that the WLAN configs are identical?

Does not make any sense to me to configure the ACLS on the foreign but can someone confirm?

Silva

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Posted August 9, 2012 at 11:27 PM
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