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Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sat Apr 29, 2017 2:26 am
by sterling
This is one a Mikrotik CCR DHCP server handing out public IP addresses on a pool.

I have a client, I think an Apple router MAC 20:C9:D0:11:56:F0, that the DHCP says "declines IP address x.x.x.x" several times a second.

I have it on static assignment.

If I take it off static assignment, it just starts cycling through all available IP addresses in the DHCP pool.
Which is horrible, so I'm glad it's on static assignment.

If I cut off Ethernet to client device upstream, it stops for a while, then starts back up eventually.

Not sure what to do other than send someone over there to update the router, or secretly brick it and tell the customer to get a new one, lol!

Anyone seen this?

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 4:47 am
by jarda
What is your lease period? Maybe it is too short...

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 6:45 am
by sterling
Two days.

This is like bursts of 10-20 events a second.

Definately something going on between the Mikrotik DHCP server and their crappy Apple client router.

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 6:46 am
by sterling
Two days.

This is like bursts of 10-20 events a second.

Definitely something going on between the Mikrotik DHCP server and their crappy Apple client router.

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 7:44 am
by jarda
Is your dhcp server authoritative? Isn't there any other dhcp server in your network?

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 10:39 pm
by sterling
Yeah, its authoritative. I check regularly for rogue dhcp with the Mikrotik Alert feature.

But most of my switches and devices have DHCP Snooping and filters already.

I just think this is a broken router, but I've never seen this behavior before.

It's the only one.

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 10:44 pm
by pe1chl
I just think this is a broken router, but I've never seen this behavior before.
It's the only one.
It is something particular to Apple devices. Probably some deviation from the standard.

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Sun Apr 30, 2017 11:49 pm
by gyropilot
This is one a Mikrotik CCR DHCP server handing out public IP addresses on a pool.

I have a client, I think an Apple router MAC 20:C9:D0:11:56:F0, that the DHCP says "declines IP address x.x.x.x" several times a second.
...
Anyone seen this?
sterling,

I see this behavior often with my hAP ac Lite and various Apple devices... especially iPhones. Doesn't really seem to cause any real problems, other than fill up the log.

John

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Thu Nov 22, 2018 2:55 am
by Wyz4k
I don't believe this is an Apple issue. It wasn't in my case.

Please see my post here: viewtopic.php?f=7&t=96472&p=699200#p699200

Re: Seen this? DHCP Server logs client declines IP several times a second?

Posted: Thu Nov 22, 2018 12:52 pm
by pe1chl
There are likely different possible issues.
However, on a large "guest wifi" network I have here at work the only troublemakers are Apple devices.
(whenever I note those DHCP "declined" or "unsuccessful" messages in the log, the MAC address always refers to Apple)