IP-forwarding (help)

[Arno J. Klaassen]

Petar Bogdanovic <petar at smokva.net> writes:

> On Wed, Jun 04, 2008 at 11:06:01PM +0200, Arno J. Klaassen wrote:
> > 
> > Hello,
> > 
> > this is probably a FAQ and/or I'm to tired, but I'd be pleased
> > if anyone can tell me what I do wrong :
> > 
> > I have a box with two interfaces, one connected to my lan
> > (172.16. ), one to a test-box (192.168.1.1) :
> > 
> >   em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> >         options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
> >         ether xxx
> >         inet 172.16.1.240 netmask 0xffffff00 broadcast 172.16.1.255
> >         media: Ethernet autoselect (1000baseTX <full-duplex>)
> >         status: active
> > 
> >   em1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> >         options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
> >         ether xxx
> >         inet 192.168.1.254 netmask 0xffffff00 broadcast 192.168.1.255
> >         media: Ethernet autoselect (1000baseTX <full-duplex>)
> >         status: active
> > 
> > 
> > I enable ip.forwarding :
> > 
> >   # sysctl net.inet.ip.forwarding
> >   net.inet.ip.forwarding: 1
> > 
> > 
> > And this is my routing table :
> > 
> >  Internet:
> >  Destination        Gateway            Flags    Refs      Use  Netif Expire
> >  default            172.16.1.254       UGS         0       20    em0
> >  127.0.0.1          127.0.0.1          UH          0        0    lo0
> >  172.16.1.0/24      link#3             UC          0        0    em0
> >  172.16.1.6         xxxxxxxxxxxxxxxxx  UHLW        1       87    em0   1194
> >  172.16.1.230       xxxxxxxxxxxxxxxxx  UHLW        1      286    em0    572
> >  172.16.1.240       xxxxxxxxxxxxxxxxx  UHLW        1        0    lo0
> >  172.16.1.254       xxxxxxxxxxxxxxxxx  UHLW        2        0    em0    487
> >  192.168.1.0/24     link#4             UC          0        0    em1
> >  192.168.1.1        xxxxxxxxxxxxxxxxx  UHLW        1        2    em1    616
> >  192.168.1.254      xxxxxxxxxxxxxxxxx  UHLW        1        0    lo0
> > 
> > For this I added to rc.conf :
> > 
> >   static_routes="test lan"
> >   route_test="-net 192.168.1.0/24 192.168.1.254" 
> >   route_lan="-net 172.16.1.0/24 172.16.1.240"
> 
> I'm pretty sure that you don't need these three lines. Turning
> net.inet.ip.forwarding on should be enough.

That's what I thought? Without the above lines it doesn't work either.
And ip.forwarding "works" in the sense trafic goes from 192.168.1.254
forward to 172.16.1.240 over lo0, but then taking "link#3" to go
to 172.16.1.0/24 fails.
I feel this is /me still not fully understand routing tables. 

NB, this is on 7-stable-amd64

Arno