Re: arp_proxy does not work with static DHCP/PERM arp ?

Hello,

Wojciech Ziniewicz a écrit :
> Yesterday after starting using arp_proxy i've received many lines like
> this (in syslog) :
>
> Sep 30 21:15:28 beta dhcpd: DHCPDISCOVER from 00:17:08:49:22:80 via eth1
> Sep 30 21:15:28 beta dhcpd: DHCPOFFER on 10.100.1.21 to
> 00:17:08:49:22:80 via eth1
> Sep 30 21:15:28 beta dhcpd: DHCPREQUEST for 10.100.1.21 (10.100.0.1)
> from 00:17:08:49:22:80 via eth1
> Sep 30 21:15:28 beta dhcpd: DHCPACK on 10.100.1.21 to 00:17:08:49:22:80 via eth1
> Sep 30 21:15:29 beta dhcpd: DHCPDECLINE of 10.100.1.21 from
> 00:17:08:49:22:80 via eth1: not found
[...]
> after switching:
>
> net.ipv4.conf.all.proxy_arp = 0
>
> to :
>
> net.ipv4.conf.all.proxy_arp = 1
>
> the above logs started to appear...
>
> NAturally clients can't obtain IP address and don't have internet access.
> What's wrong ? Can't I use proxy arp with static DHCP/static ARP ?
> Why does my DHCP server decline to assign an IP address to a host
> after makingh my router an arp_proxy ?

It's the client which declines the offered IP address, not the server.
My guess is that the client checks that the offered IP address is not
already in use by issuing an ARP request and expecting no reply. When
the router has proxy_arp enabled, it replies to the ARP request so the
client believes the IP address is in use and declines the offer.

You can check by running a packet sniffer on the client.

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