Date: 07 Sep 2005 10:06:46 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: Ihsan Dogan <ihsan@dogan.ch> Cc: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Re: dhcrelay is setting the relay ip address wrong Message-ID: <44fyshnf9l.fsf@be-well.ilk.org> In-Reply-To: <20050905214641.GA28018@dogan.ch> References: <20050905214641.GA28018@dogan.ch>
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Ihsan Dogan <ihsan@dogan.ch> writes: > Hello, > > I'm running a small router/firewall on a FreeBSD 5.4 system. This > machine should also act as a DHCP gateway. For the dhcp relay, > I'm using ISC's dhcrelay (from Ports isc-dhcp3-relay-3.0.3). > > The Interfaca and network configuration: > hme0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > options=b<RXCSUM,TXCSUM,VLAN_MTU> > inet 213.144.141.145 netmask 0xfffffff8 broadcast 213.144.141.151 > inet6 fe80::a00:20ff:feb4:42cc%hme0 prefixlen 64 scopeid 0x1 > inet6 2001:470:1f01:569::1 prefixlen 112 > ether 08:00:20:b4:42:cc > media: Ethernet autoselect (100baseTX <full-duplex>) > status: active > hme1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > options=b<RXCSUM,TXCSUM,VLAN_MTU> > inet 192.168.23.1 netmask 0xffffff00 broadcast 192.168.23.255 > inet6 fe80::a00:20ff:feb4:42cd%hme1 prefixlen 64 scopeid 0x2 > ether 08:00:20:b4:42:cd > media: Ethernet autoselect (100baseTX <full-duplex>) > status: active > hme2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > options=b<RXCSUM,TXCSUM,VLAN_MTU> > inet 192.168.42.1 netmask 0xffffff00 broadcast 192.168.42.255 > inet6 fe80::a00:20ff:feb4:42ce%hme2 prefixlen 64 scopeid 0x3 > ether 08:00:20:b4:42:ce > media: Ethernet autoselect (100baseTX <full-duplex>) > status: active > > The DHCP server is on the subnet of hme0; the DHCP clients are on > hme1 on hme2. > > netstat -rnf inet: > Destination Gateway Flags Refs Use Netif Expire > default 213.144.128.205 UGS 0 250630 tun0 > 127.0.0.1 127.0.0.1 UH 0 71 lo0 > 192.168.23 link#2 UC 0 0 hme1 > 192.168.23.2 00:c0:49:5a:1d:ca UHLW 0 2 hme1 823 > 192.168.42 link#3 UC 0 0 hme2 > 213.144.128.205 213.144.146.12 UH 1 0 tun0 > 213.144.141.144 ff:ff:ff:ff:ff:ff UHLWb 0 3 hme0 => > 213.144.141.144/29 link#1 UC 0 0 hme0 > 213.144.141.146 00:08:c7:3a:df:a9 UHLW 0 104123 hme0 233 > 213.144.141.147 00:07:e9:14:1a:a1 UHLW 0 38011 hme0 322 > 213.144.141.151 ff:ff:ff:ff:ff:ff UHLWb 0 1 hme0 > > The dhcrelay is started with the following options: > /usr/local/sbin/dhcrelay -i hme1 -i hme2 -d -a 213.144.141.146 > > The dhcrelay receives the request and passes them to the DHCP > server, but the forwarded package contains the "relay agent ip > address" of 192.168.23.1 and not 213.144.141.145 how it should > be. In that case, the DHCP server is sending the reply to > 192.168.23.1 and not to 213.144.141.145. > > Did I something wrong? A bug? The relay agent is acting exactly the way it should. When it gets a DHCP request in from a client, it uses its own address ON THE CLIENT'S NETWORK for the relay agent address. This way, the DHCP server can tell which network the client is on, and thus which set of addresses to use for assigning an address to the client. What is the problem?
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