Re: [Dnsmasq-discuss] Constant DHCPOFFER and DISCOVER in logs

2018-12-31 Thread Simon Kelley
On 31/12/2018 21:39, Jon Anderson wrote:
> Hello all,
> 
> I wanted to setup a PiHole for blocking ads and for the ability to
> modify DNS settings network-wide. I have just switched my ISP to AT
> fiber where we are required to use a supplied modem/router (ARRIS
> BGW210-700) which does not allow setting DNS servers manually. I was
> happy to find out that I could get around this by moving DHCP services
> to PiHole. I disabled the DHCP on the ARRIS and enabled the service on
> the PiHole. And now every device is using the PiHole for DNS with an
> upstream DNS from Cloudflare instead of AT’s slow DNS.
> Everything is working fine.
> When I look at the pihole-log though, I see pages and pages of this:
> 
> Dec 30 05:47:09 dnsmasq-dhcp[598]: DHCPOFFER(eth0) 192.168.1.102
> 88:96:4e:xx:xx:xx
> Dec 30 05:47:10 dnsmasq-dhcp[598]: DHCPDISCOVER(eth0) 88:96:4e:xx:xx:xx
> Dec 30 05:47:10 dnsmasq-dhcp[598]: DHCPOFFER(eth0) 192.168.1.102
> 88:96:4e:xx:xx:xx
> Dec 30 05:47:10 dnsmasq-dhcp[598]: DHCPDISCOVER(eth0) 88:96:4e:xx:xx:xx
> 
> Always the same IP. Always the same MAC address. Always between 1 and 3
> seconds apart.
> I never get anything other than OFFER and DISCOVER. It looks similar to
> the problems
> in 
> https://www.mail-archive.com/dnsmasq-discuss@lists.thekelleys.org.uk/msg03282.html
> and 
> https://www.mail-archive.com/dnsmasq-discuss@lists.thekelleys.org.uk/msg00849.html.
> It does not seem to be the same problem reported by Marc Elbirt only a
> few moments ago, though there are some similarities.
> 
> I did some digging about MAC addresses and found that the MAC address
> can tell you about the manufacturer of the device. I discovered that
> 88:96:4e corresponds to ARRIS. I checked the modem/router on it’s status
> page and found that the MAC addresses for the 2.4Ghz AP, the Guest
> network AP, and the 5Ghz AP are all very similar to the MAC address that
> seems to be having problems.
> So this seems pretty conclusive that the device that will not accept
> it’s IP address is part of the modem/router, but I’m not sure what it is
> or how to get it to accept the 192.168.1.102 or stop requesting an IP
> altogether.
> 

That looks like a client bug: it should at least do exponential back-off.


You could try using dhcp-mac and dhcp-ignore to configure dnsmasq to
just ignore requests from the offending MAc address.

Cheers,

Simon


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[Dnsmasq-discuss] Constant DHCPOFFER and DISCOVER in logs

2018-12-31 Thread Jon Anderson
Hello all,

I wanted to setup a PiHole for blocking ads and for the ability to modify
DNS settings network-wide. I have just switched my ISP to AT fiber where
we are required to use a supplied modem/router (ARRIS BGW210-700) which
does not allow setting DNS servers manually. I was happy to find out that I
could get around this by moving DHCP services to PiHole. I disabled the
DHCP on the ARRIS and enabled the service on the PiHole. And now every
device is using the PiHole for DNS with an upstream DNS from Cloudflare
instead of AT’s slow DNS.
Everything is working fine.
When I look at the pihole-log though, I see pages and pages of this:

Dec 30 05:47:09 dnsmasq-dhcp[598]: DHCPOFFER(eth0) 192.168.1.102
88:96:4e:xx:xx:xx
Dec 30 05:47:10 dnsmasq-dhcp[598]: DHCPDISCOVER(eth0) 88:96:4e:xx:xx:xx
Dec 30 05:47:10 dnsmasq-dhcp[598]: DHCPOFFER(eth0) 192.168.1.102
88:96:4e:xx:xx:xx
Dec 30 05:47:10 dnsmasq-dhcp[598]: DHCPDISCOVER(eth0) 88:96:4e:xx:xx:xx

Always the same IP. Always the same MAC address. Always between 1 and 3
seconds apart.
I never get anything other than OFFER and DISCOVER. It looks similar to the
problems in
https://www.mail-archive.com/dnsmasq-discuss@lists.thekelleys.org.uk/msg03282.html
and
https://www.mail-archive.com/dnsmasq-discuss@lists.thekelleys.org.uk/msg00849.html
.
It does not seem to be the same problem reported by Marc Elbirt only a few
moments ago, though there are some similarities.

I did some digging about MAC addresses and found that the MAC address can
tell you about the manufacturer of the device. I discovered that 88:96:4e
corresponds to ARRIS. I checked the modem/router on it’s status page and
found that the MAC addresses for the 2.4Ghz AP, the Guest network AP, and
the 5Ghz AP are all very similar to the MAC address that seems to be having
problems.
So this seems pretty conclusive that the device that will not accept it’s
IP address is part of the modem/router, but I’m not sure what it is or how
to get it to accept the 192.168.1.102 or stop requesting an IP altogether.

Thanks,
Jon
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