ArubaOS and Controllers

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MVP
Posts: 778
Registered: ‎03-25-2009

DHCP offer being dropped by APs?

Anyone encounter this issue before and found a solution?
Our customer running v5.0.3.3 on a master-local setup of A6000-SC1's.

Since the upgrade (with new config) we're getting tons of users that are unable to get an ip address until we reboot the AP it is connected on. These seems to happen pretty much random across the ~150 AP/~1500 users.
From debug/sniffing we can see the client sending the DHCP discover. We can also see the DHCP offer in the AP-packetcapture, but this offer does not arrive at the client according to wireshark.

Upgrading the controller to v5.0.4 did nothing to resolve the issue.
Rebooting the AP the user is connected on does fix the issue (temporarily).

Support (the other vendor) hasn't been able to provide a solution for nearly a month now and we're inches away from throwing an antiquated flashbackup back on it and never touching the boxes again which I would like to avoid.
Koen (ACMX #351 | ACDX #547 | ACCP)

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Guru Elite
Posts: 21,512
Registered: ‎03-29-2007

Re: DHCP offer being dropped by APs?

How many users are in the same VLAN on this WLAN?
What DHCP server are you using?
What is the lease time of the users?


Colin Joseph
Aruba Customer Engineering

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MVP
Posts: 778
Registered: ‎03-25-2009

Re: DHCP offer being dropped by APs?


How many users are in the same VLAN on this WLAN?
What DHCP server are you using?
What is the lease time of the users?




the biggest vlan will have up to ~500 users in it at one time. Issue also happens on smaller vlans though.
2 windows dhcp servers each serving half the subnet (for redundancy)
lease time is 1 day

We can also see the offer from both dhcp servers going back to the client (up untill the AP) so its not a lack of dhcp addresses.
Koen (ACMX #351 | ACDX #547 | ACCP)

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Guru Elite
Posts: 21,512
Registered: ‎03-29-2007

Re: DHCP offer being dropped by APs?

That is a particularly difficult issue to troubleshoot. Just like interference, congestion and contention can cause packet drops, the same thing can apply to DHCP. Rebooting the access point knocks clients off of those access points, which reduces contention and congestion, so sometimes that gives the appearance of "resetting" things. Is DHCP the ONLY thing that is not working?

The best thing to do is to turn on user debugging and setup a syslog server. The next time it happens, the Aruba controller will have a log that will detail the authentication as well as DHCP process and the log can be searched to see exactly what is going on.

There are a number of issues that could be in play:

- Multiple DHCP server issues
- Congestion and contention
- Client-side issues at the time

Turning on user debugging will allow us to narrow down what is going on.


Colin Joseph
Aruba Customer Engineering

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

MVP
Posts: 778
Registered: ‎03-25-2009

Re: DHCP offer being dropped by APs?

The case got escalated from purple all the way up to orange so hopefully that will get some results soon.
Koen (ACMX #351 | ACDX #547 | ACCP)

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QLD
Occasional Contributor II
Posts: 14
Registered: ‎07-21-2011

Re: DHCP offer being dropped by APs?

Was this problem ever fixed? I am seeing the same issue.

Q.
MVP
Posts: 778
Registered: ‎03-25-2009

Re: DHCP offer being dropped by APs?


Was this problem ever fixed? I am seeing the same issue.

Q.




Nope.

Infrastructure was master-local A600-SC1's with 150 AP-70's.
After upgrading to 5.0.3.3 the DHCP issue started. Upgrading further to 5.0.4.0 and 5.0.4.1 did nothing to resolve the issue.

In the end we downgraded to the original 3.4.3.0 version which has resolved the problem for now while Aruba investigates the issue further.
Koen (ACMX #351 | ACDX #547 | ACCP)

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-- Problem Solved? Click "Accept as Solution" in a post.
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