Date: Fri, 7 Dec 2012 11:38:45 +0000 From: Tom Evans <tevans.uk@googlemail.com> To: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Using dhclient on WAN if on a box serving DHCP to LAN if Message-ID: <CAFHbX1LViMrh95sAm3uMJ1dt3RtUwKbPCtHQCTU2xaALaf7n7A@mail.gmail.com>
next in thread | raw e-mail | index | archive | help
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? 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAFHbX1LViMrh95sAm3uMJ1dt3RtUwKbPCtHQCTU2xaALaf7n7A>