Orbi WiFi 7 RBE973
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Public Service Announcement - DHCP requests still an issue

donawalt
Virtuoso

Public Service Announcement - DHCP requests still an issue

You may notice this if you have Apple devices in your home....if you check the logs, you will see a LOT of DHCP request entries in there for Apple products!

 

Some have said it's due in part because Apple products by default have a setting to use a "Private IP address", which changes the advertised MAC address to reduce tracking across networks. However, this is not true - both in testing, and in theory. The private MAC address only changes when the device is power cycled,  or the network is "forgotten" and reconnected - both of which are likely very infrequent for most devices.

 

In my case, maybe 5 devices have about 55-60 DHCP requests in a week - about 8 a day. But one iPad had 225 DHCP requests in the last week! That's 32 a DAY.

 

Luckily this seems to have no impact on network performance, which is why Netgear is not addressing it. You can also create a static IP address outside the router's address pool range for an offending device, if you are concerned. Maybe other network vendors have the same issue, I don't know.

Message 1 of 10
CrimpOn
Guru

Re: Public Service Announcement - DHCP requests still an issue


@donawalt wrote:

Luckily this seems to have no impact on network performance, which is why Netgear is not addressing it. You can also create a static IP address outside the router's address pool range for an offending device, if you are concerned.


Netgear cannot "address" a device repeatedly making DHCP requests.  A device sends a DHCP request and the DHCP server responds.  What would we have Netgear do?  Not respond and let the device drop off the network?

 

A static IP address set on the device would stop the behavior, but using the LAN setup process to define an IP outside of the DHCP pool does not change the fact that the device does not follow the DHCP protocol and wait until the lease is half expired before asking to renew it. The device will still use DHCP to get that assigned IP.

 

 

Message 2 of 10
donawalt
Virtuoso

Re: Public Service Announcement - DHCP requests still an issue

I think you are making assumptions as to what is going on here, which of course may or may not be true. Having been in software development for over 40 years and being bitten by surprising bugs, and developing many test harnesses to validate code, I think of several reason besides your suggestion that could be the cause - none of this of course will we know what's the truth without access to the specific data going between device and router:

 

1 - a FW bug could be causing the lease information sent to the device to be incorrect;

2- DHCP requests could be rejected improperly (this seems plausible too because I have seen in the logs the DHCP requests often times come in a flurry, many requests within minutes;

3- bug/issue could be breaking the integrity of the DHCP request message, causing retries/reissues;

 

There could be device side bugs too - thinking it has to get another DHCP every time the device wakes up, or switches between router/satellite, malformed DHCP request messages, etc. etc. - many many possibilities

 

That said, wouldn't it be nice, especially since many of us were in the beta test group, for Netgear to actually investigate the issue and reply what they found - even if it's a problem on the device side. Then we would know and possibly know how to get around it. But we know that won't happen.

Message 3 of 10
CrimpOn
Guru

Re: Public Service Announcement - DHCP requests still an issue

Good points.  A bit strange that only Apple products appear to be affected, which might skew the investigation more toward the device than the DHCP server.  But you are entirely correct.  Examining the actual DHCP packets is the only methodology that would uncover much.

 

Investigating network issues with WiFi devices is so much more cumbersome than wired devices.  It is almost trivial to mirror a switch port to a PC and use Wireshark to capture every DHCP packet that goes across the network (while ignoring everything else).  WiFi clients are more of a hassle.

 

It is also frustrating that using the Debug feature to capture LAN/WAN traffic is not useful because of the limited space available to store the capture.  My ancient RBR50 (version 1) has an option to store the debug log to the USB port (which newer Orbi models do not have.)  I plugged a 32GB USB stick into the router and the LAN/WAN capture was capped at the most recent 2GB.  (My goal was to "record everything" for several days and then look through it.  Not happening!)

 

 

Message 4 of 10
donawalt
Virtuoso

Re: Public Service Announcement - DHCP requests still an issue

One other point @CrimpOn - this absolutely happens on wired devices too! And not just iOS, but Macs also. But maybe happening on Ethernet connections would make it easier to at least assess. Oh well we can dream.
Message 5 of 10
CrimpOn
Guru

Re: Public Service Announcement - DHCP requests still an issue

One does sense a pattern here.... Apple devices.  I, personally, have zero wired Apple devices, but one iPad and one iPhone are in the house.  (She who must be obeyed. Google "Rumpole of the Bailey") This will require activating a WiFi capture.

 

Several years ago (before Apple activated that "Randomize MAC" scheme, I observed an iPad requesting DHCP every two minutes.  It was simply a curiosity at the time, and I was not in a position to capture anything.)

 

 

Message 6 of 10
donawalt
Virtuoso

Re: Public Service Announcement - DHCP requests still an issue

If you do get into capturing anything and learn anything, let us know!

Message 7 of 10
CrimpOn
Guru

Re: Public Service Announcement - DHCP requests still an issue

Update:

 

Well, Wireshark does not make capturing DHCP events particularly easy.  I am now capturing every DHCP that happens over WiFi and have discovered that two of my security cameras have a disappointing habit of issuing a DHCP Discovery every 5 minutes, which causes the DHCP server to respond with an Offer (which the cameras ignore).  The camera forum has posts complaining about this odd behavior.  The company claims this is their method of determining that the network remains available.  Angry customers claim using ICMP to 'ping' the internet gateway is generally accepted method for this and that all this DHCP is filling up their server logs and causing issues.

 

With Wireshark, the process (so far) is:

Set a Capture Filter for udp port 67 or 68.

Then set a Display Filter for dhcp.option.type == 50 (which displays only Requests -- when a device wants to renew an IP address).

 

Will enable capture on wired devices next.

 

Although enjoying the activity, I am not optimistic that this will produce "results".  I have seen Apple devices make frequent DHCP requests in the past, but neither the iPhone nor the iPad in my house appear to be doing that right now.

 

As the Lock Picking Lawyer says, "That's all I have for you today."

 

 

Message 8 of 10
FURRYe38
Guru

Re: Public Service Announcement - DHCP requests still an issue

@SLK-Purdue might chime in on this as well. He did some checking into this as well. 

We have brought this to NG attention. 

Message 9 of 10
donawalt
Virtuoso

Re: Public Service Announcement - DHCP requests still an issue

Very interesting! It sure did look like DHCP protocol was being used for something out of the norm. In my router logs, DHCP messages are easily 95% or more of the messages - my original motivation to get of the unnecessary ones so I could really see what was happening with leases, see other messages more easily, etc.

Message 10 of 10
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