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Contributor II
Posts: 61
Registered: ‎02-20-2012

Remote Access Point - Fallback DHCP server (192.168.11.1) stays on

Hi everyone,

 

We have Master controller Aruba 3400 5.0.4.6,

over the MPLS network Local controller Aruba 650 5.0.4.6 at branch offices,

and AP105 (Work as RAP) attached to Local controller Aruba 650.

 

We configured Master - Local controller redundancy with AP105 RAP.

When AP105 RAP at the branch office cannot reach to Local controller at branch office,

AP105 RAP fallbacks to Master Aruba 3400 to continue the operation.

 

To configure above, we created AP Group, set LMS IP for Local controller, set Backup LMS IP for Master controller.

Checked LMS Preemption on. LMS Hold-down Period 600sec.

All other parameters we left default, including "Remote-AP DHCP Server ID 192.168.11.1" "Remote-AP DHCP Default Router 192.168.11.1", "Remote-AP DHCP Pool End 192.168.11.254" "Remote-AP DHCP Pool Netmask 255.255.255.0"

 

We installed the system above and almost 4 months has passed.

 

One day, we found that someone sent DHCP packet from IP 192.168.11.1. We tracked the MAC address and found that four AP105s out of seven AP105s (not all of them) sent DHCP packets!!

In Configuration - AP Installation screen, we selected AP and rebooted, and that DHCP behavior was stopped.

 

We checked Aruba documents and found that Remote Access Point has DHCP server option and default IP is 192.168.11.1.

DHCP server function should not working after resuming back to the normal operation (RAP AP105 connects to Local controller), but four AP105 kept sending DHCP packets.

 

To stop above behavior, I tried to delete "Remote-AP DHCP Server ID 192.168.11.1" "Remote-AP DHCP Default Router 192.168.11.1", "Remote-AP DHCP Pool End 192.168.11.254" "Remote-AP DHCP Pool Netmask 255.255.255.0" , but after clicking on Apply, those default values were back.

 

Do you know how to disable DHCP server function during fallback operation? For DHCP server function, please refer to the URL link below.

 

http://www.arubanetworks.com/techdocs/ArubaOS_60/UserGuide/Remote_AP.php#XREF_13875_Configuring_the

 

 

Guru Elite
Posts: 20,808
Registered: ‎03-29-2007

Re: Remote Access Point - Fallback DHCP server (192.168.11.1) stays on

There is also a Remote AP-DHCP Server VLAN parameter.  Change that to anything besides 1 (which is what your Bridged VLAN probably is) and it will stop answering.

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 61
Registered: ‎02-20-2012

Re: Remote Access Point - Fallback DHCP server (192.168.11.1) stays on

Hi cjoseph,

 

Thank you very much for your quick response.

I understand your solution - by entering vlan id such as "2" , then DHCP server function does not send DHCP packets to vlan1.

 

I tried to delete "Remote-AP DHCP Server ID 192.168.11.1" "Remote-AP DHCP Default Router 192.168.11.1", "Remote-AP DHCP Pool End 192.168.11.254" "Remote-AP DHCP Pool Netmask 255.255.255.0" , but after clicking on Apply, those default values were back.  Do you know how to delete those default values?  

Guru Elite
Posts: 20,808
Registered: ‎03-29-2007

Re: Remote Access Point - Fallback DHCP server (192.168.11.1) stays on

You cannot delete those Values.  A value must be in there.

 

Please change the VLAN.

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 61
Registered: ‎02-20-2012

Re: Remote Access Point - Fallback DHCP server (192.168.11.1) stays on

Hi Cjoseph,

 

Its been long since I posted last time. Our Master-Master , Master-Standby, Master-Local (with RAP) redundancy system is working very beautifully. Master Aruba 3400 with code level 5.0.4.6 has been up and running more than a year.

 

Only thing we need to fix is this subject. Sometimes, some RAP (AP-105 under local controller Aruba 650) became Remote DHCP Server, and responded to other DHCP Discover packets with 192.168.11.1 DHCP Server address.

Cjoseph suggested me to set "Remote DHCP Server VLAN" other than 1. I agreed with that solution.

 

Last Friday and today, I have been trying to reproduce remote DHCP Server mode. I assume - when RAP was disconnected from the Master controller, (In this case, Master controller is Aruba 650 located in the branch office through MPLS network, and LMS is VRRP-configured Aruba 3400s in the data center), RAP fails over to LMS IP's controller and Remote DHCP Server mode should be invoked.

 

I tried Master controller failover scenario for couple of times, and observed the packets from RAP (AP-105), but I never saw DHCP Offer or DHCP Ack packet from RAP, in response to DHCP Discovery.

 

I have a question - what triggers Remote DHCP Server mode? My understanding in Remote DHCP Server mode is, when DHCP server is not available in remote office due to the network failure, Remote DHCP Server mode is invoked in RAP and pc clients can lease DHCP IP address from RAP. If my understanding is correct, network failure event, such as Master - LMS failover should trigger Remote DHCP Server mode.

 

If you know the principal of the operation of Remote DHCP Server mode, I much appreciate it.

 

Regards, Mike 

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