Topic: dhcp dhclient polling problem

[louhaven]

Hello everyone,

The dhclient running on my gateway is constantly polling my isp's dhcp server, slowing down my internet connection.

Details:

I'm seeing constant flashing on the NTD - network terminating device, indicating that either my gateway or the isp's dhcp server is constantly using the connection. My isp recently changed some of the properties of its dhcp service to better be able to log 'metadata' and be more effective in blocking some websites (Oz Govt like China Govt now).

contents of files /var/lib/dhclient:

dhclient-eth1.leases:

"
lease {
  interface "eth1";
  fixed-address xxx.xxx.xx.xxx;
  option subnet-mask 255.255.240.0;
  option routers xxx.xxx.xx.x;
  option dhcp-lease-time 86400;
  option dhcp-message-type 5;
  option domain-name-servers xxx.xxx.xxx.x,xxx.xxx.xxx.x;
  option dhcp-server-identifier xxx.xxx.xx.x;
  option ntp-servers xxx.xxx.xxx.x;
  renew 0 2015/5/17 10:18:48;
  rebind 0 2015/5/17 19:28:51;
  expire 0 2015/5/17 22:28:51;
}
"

dhclient-eth1.conf:
"
interface "eth1" {
    send host-name "xxxxxxxx@xxxxxxxxxxxxxx";
    send dhcp-client-identifier "xxxxxxxx@xxxxxxxxxxxxxx";
}
"

A little bit about the connection to the isp here:

Currently I am using option 1 - Dhcp send client identifier, but I dont have to:

"
SkyMesh like many others use IPoE, so your routers WAN port just needs to be set to Automatic (DHCP). make sure you're plugged from the correct UNI-D port on the NBN NTD to the WAN port on your gateway.

Because IPoE uses the port at the DSLAM for the authenitication it is tied to the CPE mac address.

The port on the NTD that supplies your internet will just give you a live IP without any authentication required.
"
So, for some reason either my end is polling the isp's Dhcp server, or the isp is constantly polling my Dhclient for some reason.

dhclient daemon is being started with the following command line:
"
/sbin/dhclient
-d -cf /var/lib/dhclient/dhclient-eth1.conf -lf /var/lib/dhclient/dhclient-eth1.
leases eth1

"

Do I need to create a custom template of the dhclient /var/lib/dhclient config files to first stop the dhclient from changing my dns settings, and is there any way to properly diagnose which end is doing the polling (I am assuming its my end) and if it is my end, is there a command line switch I should be using to try to limit the polling since I am on a static ip address.

Any help on this issue would be greatly appreciated.

I also sent an email to the network engineer who helped me with the first issue, in part I said:

"
I have concerns the way the interface is being polled constantly. the dhclient fetched the settings from your dhcp server, the new ones being saved as thus:
<snip - was leases file>
For some reason the lights on the ntd are constantly flashing, meaning there is traffic, even though nothing is running to generate this traffic.

The way it was setup before, the ip address remained static, the light remained illuminated unless there was traffic, but all this tells me is there is something generating traffic where there is no traffic request. It raises a red flag for me!
Is there a way to modify these settings so that my end doesnt continually poll your dhcp server (for what reason, I dont know), and the lights on the ntd remain solidly illuminated except for when there is traffic.

I'm not sure what kind of a hit I will be taking to my quota because of all this "Unnecessary" traffic being my end polling your dhcp server.
"

Best Regards,

Louis


Update:
--------

I was contacted this morning, by my isp. They say that the phantom traffic is "Broadcast traffic" and will not count against my quota, but are monitoring it to make sure it doesn't. It would seem they have just chaged their routers; from cisco to some other brand, and its this new brand thats causing the troubles.
The technician thought it was good that I was noticing this traffic as my setup is unique, but I am not alone. I was the only one to report it.

All in all, the loss of sleep, diagnosing to the wee small hours, has definately made me appreciate the time and effort thats gone into Sme Server, to assembling something so easy to control, so where do I donate.

-----
Best Regards,

Louis

[CharlieBrady]

I'm seeing constant flashing on the NTD - network terminating device, indicating that either my gateway or the isp's dhcp server is constantly using the connection.

Or "something" is using the connection.

I think it very unlikely that you really have a "dhclient polling problem". I think you are jumping to a wrong conclusion. A DHCP client generally won't generate any traffic between when it obtains a DHCP lease, and when it seeks to renew the lease. Since you have been given a 24 hour lease, dhclient will generate a miniscule amount of traffic.

[Stefano]

louhaven: IIRC you've been already told to give us some elements (logs etc).. you're telling "it doesn't work", "they say it doesn't work"