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Re: No DHCP for Wireless Clients

[ Edited ]

I experienced the same exact issue. I have a Server 2012 R2 DHCP server and for whatever reason, several APs were not able to allow clients to hit the DHCP server. No VLANs involved.

 

The solution I found was to forget the AP from the controller, and then use the UniFi-Discover tool to reset the AP to factory defaults. Once the reset completed, I added back the AP into the controller, ensured it provisioned properly, and it immediately began working without any DHCP issues for clients.

 

And yeah, I tried the force provision on the AP, but that didn't work - only the factory reset of the AP seems to have fixed the issue.

 

Hope this also works for all of you!!

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Re: No DHCP for Wireless Clients

I may give that a go, thanks. Doesn't scale well if you have 100s of APs though.

Looks like it's not an uncommon issue, anyone from support reading this? Happy to help if I can...
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Re: No DHCP for Wireless Clients

@g357130 @slash1 are the DHCP requests making it to the DHCP server?  I will be helpful to know where the DHCP packets are getting lost.

 

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Re: No DHCP for Wireless Clients

The DHCP requests do seem to (in most cases) hit the DHCP server (Server 2012 R2).

I'm looking at 3 clients with 169.x addresses now:

1 is repeatingly trying to renew with a valid IP
2 is trying to renew with the wrong IP (guessing stale from another network) this is getting NACKs but nothing else
3 is also trying to renew with the wrong IP (guessing stale from another network) this is getting NACKs but nothing else

I cannot see a valid lease for the clients above.

The issue seemed to start after updating the APs to 3.9.42, however I downgraded a selection of APs to 3.9.27 and the examples above are sat on the older firmware (3.9.27).

To add, there are various other clients on the same AP/SSID with valid IP addresses. The issue above doesn't seem to be affecting all clients for a specific AP which seems to reflect what tonyuaktins was also seeing.

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Re: No DHCP for Wireless Clients

[ Edited ]

Just re-read @slash1's post, and yes, the SSID we're having issues with also is configured for WPA Enterprise with 802.1x.

 

...and looking at the clients affected it only seems to be affecting AP-AC-Pros. Haven't seen any issues with clients on AP-Pros, but will keep an eye on them today.

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Re: No DHCP for Wireless Clients

@g357130 can you do a packet capture on the AP to see if the DHCP responses are making it back?

What are the clients that are having issues? (sorry if you've already mentioned that and I missed it)

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Re: No DHCP for Wireless Clients

[ Edited ]

I can see the DHCP Discover from the client, then a DHCP Offer from the DHCP server (with a valid available IP). However the client then performs another DHCP Offer. This happens over and over again, almost as if the client doesn't receive the offer (the MAC address is correct in the offer).

Nothing is reported in the DHCP log in this period, with standard logging enabled. DHCP server is Windows Server 2012 R2.

 

Client is a laptop running Windows 10 x64.

 

TeG4IHT

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Re: No DHCP for Wireless Clients

I've just performed a packet capture on the client and can only seeing DHCP Requests, confirming the theory that the client might not be seeing the offers.

If I disconnect, and reconnect to another SSID on the same AP, I can see the full DORA.
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Re: No DHCP for Wireless Clients

I have been seeing a similar problem for a while on my setup. I am running 5.9.29 with APs (AC-PRO and AC-EDU) on 5.9.54.9373. I have two SSIDs the WPA2 SSID has no DHCP issues. However, the radius SSID has daily problems where clients cannot DHCP and end up with a 169... address. If the same client switches to the WPA2 SSID, no problem. Rebooting the AP helps temporarily as well.

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Re: No DHCP for Wireless Clients

[ Edited ]

I am running 5.8.30 with all UniFi AP-AC-Pro's on 3.9.54.9373.  I am experiencing this same DHCP issue on an SSID using WPA enterprise where the radius server is redirecting this SSID to other remote radius servers.  On a different SSID (as well as VLAN), the radius server is not redirecting as it is pulling from local data - it is working fine.  I'm thinking its a timing issue on being authorized.  We did not have this issue with firmware 3.9.42.

 

*edit

I should also say, restarting the DHCP server does nothing.  Restarting the WAP helps for a little bit, but then the problem creeps back.

 

**edit - I meant firmware 3.9.40.9098 , not 3.9.42.

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Re: No DHCP for Wireless Clients

[ Edited ]

The issue is very much there in 3.9.42 for us, downgrading to 3.9.27 didn't help either.

It does seem to only be affecting AP AC Pros (and only with 802.1x/Radius), the UAP Pros don't seem to have the issue.

To add, I tried factory resetting a selection of APs, forgetting them from the controller and adopting yesterday evening as Tonyuatkins suggested. This did not help the situation for us.

Can you run Wireshark / packet capture on the client and see if like me, you're not receiving the DHCP Offers back from the DHCP server?

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Re: No DHCP for Wireless Clients

[ Edited ]

Sorry, i meant firmware 3.9.40.9098.  I already reverted all of my AP -AC Pros back to 3.9.40.9098 and so far I have not had an instance of DHCP not working with clients that use 802.1x (radius) - no more 169 addresses...  Kind of late for me to do wireshark, but I think it is fair to say there is no way they received a DHCP.  I'm sure they sent it, just not received.

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Re: No DHCP for Wireless Clients

[ Edited ]

@g357130 are you using any VLAN's? You can also use tcpdump on the AP itself to see where the packet is getting dropped.

 

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Re: No DHCP for Wireless Clients

No VLANs for this SSID. The screenshot in post 47 was from a tcpdump on the AP, you can see that the AP sees both the Discover and Offer, however when performing a packet capture the client does NOT see the Offer (post 48).

So, the Offer is getting lost between AP -> Client.
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Re: No DHCP for Wireless Clients

Was having this issue last week. Adding MAC of DHCP server to "Block LAN to WAN Multicast" exception list solved this problem.

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Re: No DHCP for Wireless Clients

[ Edited ]

@BrackishClog wrote:

Was having this issue last week. Adding MAC of DHCP server to "Block LAN to WAN Multicast" exception list solved this problem.



Isn't this only true if you have Block LAN to WAN Multicast enabled?

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Re: No DHCP for Wireless Clients

[ Edited ]

Would have thought so (it's not enabled here, so I don't believe this will help).

3.9.40.9098 still working well for you @blazenmp?

 

@UBNT-BenBuckleydo you need anything else?

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Re: No DHCP for Wireless Clients

@g357130 which interface was that on the AP?  

 

What I'm trying to have you confirm is where the packet gets dropped.  Do doing a packet capture on the client would, help.  Or even better, doing an 802.11 capture. 

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Re: No DHCP for Wireless Clients

@UBNT-BenBuckley the packet capture was using the br0 interface on the AP.

I've performed a packet capture on both the client and the AP (have mentioned that a few times above, might be worth re-reading my earlier posts).

But essentially:
Packet capture on the AP (br0) = DHCP Discover and DHCP Offer packets
Packet capture on the client = Only DHCP Discover packet

No DHCP Offer packets are received by the client, despite the AP seeing them so I can only conclude with the information that I currently have that the AP is dropping the Offer packet for some reason.
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Re: No DHCP for Wireless Clients

@g357130 sorry for misreading your posts... you'd mentioned a "theory" about the client not getting the pacekts, I was unaware that you'd actually done a packet capture there.

 

Can you do a tcpdump on the AP for the athX interface that the client is trying to connect to?  If the AP is dropping them then you should not see the packet on the ath interface, even though it is present on br0.

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