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Emerging Member
Posts: 47
Registered: ‎03-06-2017
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DHCP Requests

Hello,

 

I have gotten several radios now that are recieving an unusual ammount of DHCP requests in the logs.  Below is just a small sample of the logs, it goes many days with requests that seem to happen every 5 minutes.  Is this the customer router causing this issue? dtfarm is the router in question here.

 

Mar 13 05:32:12 dnsmasq-dhcp[989]: DHCPREQUEST(eth0) 192.168.11.144 60:38:e0:76:2a:5f
Mar 13 05:32:12 dnsmasq-dhcp[989]: DHCPACK(eth0) 192.168.11.144 60:38:e0:76:2a:5f dtfarm
Mar 13 05:37:15 dnsmasq-dhcp[989]: DHCPREQUEST(eth0) 192.168.11.144 60:38:e0:76:2a:5f 
Mar 13 05:37:15 dnsmasq-dhcp[989]: DHCPACK(eth0) 192.168.11.144 60:38:e0:76:2a:5f dtfarm
Mar 13 05:42:17 dnsmasq-dhcp[989]: DHCPREQUEST(eth0) 192.168.11.144 60:38:e0:76:2a:5f 
Mar 13 05:42:17 dnsmasq-dhcp[989]: DHCPACK(eth0) 192.168.11.144 60:38:e0:76:2a:5f dtfarm
Mar 13 05:47:20 dnsmasq-dhcp[989]: DHCPREQUEST(eth0) 192.168.11.144 60:38:e0:76:2a:5f 
Mar 13 05:47:20 dnsmasq-dhcp[989]: DHCPACK(eth0) 192.168.11.144 60:38:e0:76:2a:5f dtfarm
Mar 13 05:52:23 dnsmasq-dhcp[989]: DHCPREQUEST(eth0) 192.168.11.144 60:38:e0:76:2a:5f 
Mar 13 05:52:23 dnsmasq-dhcp[989]: DHCPACK(eth0) 192.168.11.144 60:38:e0:76:2a:5f dtfarm
Mar 13 05:57:26 dnsmasq-dhcp[989]: DHCPREQUEST(eth0) 192.168.11.144 60:38:e0:76:2a:5f 
Mar 13 05:57:26 dnsmasq-dhcp[989]: DHCPACK(eth0) 192.168.11.144 60:38:e0:76:2a:5f dtfarm
ubnt question dhcp.PNG

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Established Member
Posts: 1,549
Registered: ‎12-05-2010
Kudos: 169
Solutions: 15

Re: DHCP Requests

[ Edited ]

First renew request is sent in half time of leased time...that is how dhcp works...that is why 5 mins.

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Ubiquiti Employee
Posts: 9,482
Registered: ‎04-14-2017
Kudos: 1766
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Re: DHCP Requests

Probably the fastest way to figure this out is to see what that IP address is and where it is located. Is it a device in your network or is it beyond the CPE?
Emerging Member
Posts: 47
Registered: ‎03-06-2017
Kudos: 6
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Re: DHCP Requests

The IP is coming from the CPE and sending it downstream to the customer router.  Our CPE is in router mode so it has a DHCP scope assigned.

ubnt question dhcp2.PNG
ubnt question dhcp3.PNG
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New Member
Posts: 30
Registered: ‎11-20-2016
Kudos: 4

Re: DHCP Requests

looks like you need to change your lease time from 600 seconds to 43200 (12hrs) or 86400 (24hrs)

Emerging Member
Posts: 47
Registered: ‎03-06-2017
Kudos: 6
Solutions: 1

Re: DHCP Requests

[ Edited ]

I will try this, although...I do not see how this is the problem, 600 seconds would be 10 minutes, and the logs show it renewing on a 5min basis, unless I am interpreting the logs wrong.

Established Member
Posts: 1,549
Registered: ‎12-05-2010
Kudos: 169
Solutions: 15

Re: DHCP Requests

[ Edited ]

First renew request is sent in half time of leased time...that is how dhcp works...that is why 5 mins.

Emerging Member
Posts: 47
Registered: ‎03-06-2017
Kudos: 6
Solutions: 1

Re: DHCP Requests

Thank you,

 

changing lease time seems to fix this.  I do not remember ever seeing this on our radio logs before.  Most of our radios are set to 600 second lease time.  Perhaps a recent firmware change started logging these requests and before they were not logged?

Established Member
Posts: 1,549
Registered: ‎12-05-2010
Kudos: 169
Solutions: 15

Re: DHCP Requests

Recently UBNT changed DHCP loging mode to more detailed...

Emerging Member
Posts: 47
Registered: ‎03-06-2017
Kudos: 6
Solutions: 1

Re: DHCP Requests

Thank you, we have been looking at changing the lease time for some time now, and with the recent log change it is flooding all of our logs, any suggestion on a lease time we should set? 12hrs as mentioned above seems pretty solid

Established Member
Posts: 1,549
Registered: ‎12-05-2010
Kudos: 169
Solutions: 15

Re: DHCP Requests

It depends on LAN scenario behind your UBNT unit...more leased time will cause problems for networks stations/routers when you will have to change some network settings like static DHCP reservations or whole subnet... very short leased time is required for places with a lot of different network clients per day/hour (typicaly restaurant, airport,...).

Emerging Member
Posts: 47
Registered: ‎03-06-2017
Kudos: 6
Solutions: 1

Re: DHCP Requests

very helpful thank you... i think in most of our cases there are very few clients coming and going (very rural area) in which we can probably set to the max lease time.

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