Date: Fri, 7 Dec 2012 12:14:04 +0000 From: Bob Bishop <rb@gid.co.uk> To: Tom Evans <tevans.uk@googlemail.com> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: Using dhclient on WAN if on a box serving DHCP to LAN if Message-ID: <D8BBB8C9-8A8D-44BC-978E-7019BE4ED5B3@gid.co.uk> In-Reply-To: <CAFHbX1LViMrh95sAm3uMJ1dt3RtUwKbPCtHQCTU2xaALaf7n7A@mail.gmail.com> References: <CAFHbX1LViMrh95sAm3uMJ1dt3RtUwKbPCtHQCTU2xaALaf7n7A@mail.gmail.com>
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Hi, On 7 Dec 2012, at 11:38, Tom Evans wrote: > Hi all > > Using 9.0-STABLE #1 r230946 - I found it out as I rebooted to prepare > for 9.1, but I think it should be largely irrelevant of version. > > I have a freebsd router that provides all the things a soho router > should on its LAN iface - DNS, DHCP, NAT (via pf). The WAN iface > connects to a ADSL modem operating in bridge mode. > > My ISP has recently forced a change on to me, in order to get service > I have to connect via DHCP, in order for them to give me my static IP. > Apparently this makes their lives a lot easier. Even knowing the IP, > netmask, broadcast and router is not enough, no service will flow > unless a DHCP request has been registered. > > Relevant rc.conf, ale0 is the WAN, em0 is the LAN > > ifconfig_ale0="DHCP" > ifconfig_em0="inet 192.168.1.1 netmask 255.255.255.0" > gateway_enable="YES" > > dhcpd_enable="YES" > dhcpd_flags="-q" > dhcpd_ifaces="em0" > dhcpd_conf="/usr/local/etc/dhcpd.conf" > > With this configuration, the default route is over the LAN iface. This > causes the dhclient for ale0 to get a response from the local dhcpd > server, not the ISP dhcpd server. This drove me potty! Can anyone > explain why dhcpd, having been told only to listen for DHCP on em0, > responds to ale0? Could this be related to my pf rules, or is it down > to the default route being incorrect? > > Changing rc.conf to this allows the network to come up correctly: > > ifconfig_ale0="inet xx.xx.110.172 netmask 255.255.255.0 broadcast > xx.xx.110.255 DHCP" > defaultrouter="xx.xx.110.1" > > This relies on me knowing that these are the values that dhclient on > the WAN iface will receive from my ISP's DHCP server. How would I > achieve this setup if this information was dynamic or otherwise > unknowable? My ISP could easily change my gateway IP, the only > guarantee I have is that my allocated IP is static. > > So: > > 1) Why does the LAN dhcpd respond to the WAN dhclient? Maybe DHCP requests are getting passed across the gateway. Try setting gateway_enable="NO" temporarily, if that stops the unwanted behaviour then configure pf to block DHCP requests crossing the gateway. > 2) Is there a better way of specifying this setup, so that it does not > have hard coded addresses in there? > > Thanks in advance for any pointers. > > Tom > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" > -- Bob Bishop rb@gid.co.ukhelp
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