On Wed, Dec 15, 2021 at 04:26:42PM +0100, Tuxo wrote: > Hi list > > My router and my docsys modem power on at the same time. the modem is > handing out dhcp offers of 192.168.100/24 . I assume they are meant for > internal set up purposes and dhclient on my router should not catch or > respond to them. Only the final offer after modem bootup has completed does > contain the WAN subnet and a lease time of 4 hours. > > Can I configure dhclient on my router to discard lease offers from a certain > subnet? I could also try to match the lease time, the 192.168.100/24 lease > time is only several seconds (!!) short, the real one will be 4 hours or > more and come with a valid WAN subnet mask. > > I never had this problem before, so I don't know how to change dhclient's > behaviour to a bogus lease offer. > > Maybe iptables could assist and block multicast traffic from/to the wrong > subnet? I'm not sure I would still get the actual WAN lease then.
Which dhcp client? if dhclient, the config allows specifying a reject subnet range, so you could do something like: reject 192.168.100.0/24 -- Len Sorensen