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dhcp_spoof and default gateway
- To: misc_(_at_)_openbsd_(_dot_)_org
- Subject: dhcp_spoof and default gateway
- From: Antoine Jacoutot <ajacoutot_(_at_)_lphp_(_dot_)_org>
- Date: Fri, 26 Nov 2004 16:18:19 +0100
I'm having a small routing problem under OpenBSD.
I'm using an Adsl modem/router to connect to the internet. To avoid using ppp
on OpenBSD as well as not using the router built-in NAT and all (so I can use
PF), I configured the modem for dhcp_spoof. This is a mode were when the
modem connects to the ISP, the wan adress is passed to the pluged-in computer
after issuing a dhcp request.
I do not have any problem using this mode under Windows and Linux (I tried
both to make sure it was working fine) but under OpenBSD it does not work.
Note that I have a fixed IP, so I don't even need to issue a dhcp request to
the modem (this also works under Windows and Linux).
After searching for a while, I think I found where the problem lies: the
default gateway is not on the same subnet (which does not seem to be a
problem for the other OSes).
Here's an exemple configuration:
default GW: 18.104.22.168
What I did to configure the interface and add the default gateway was:
ifconfig rl0 inet 22.214.171.124 netmask 255.255.255.255
route add -host 126.96.36.199 188.8.131.52
# I also tried route add 184.108.40.206 -interface 220.127.116.11
# I tried to play with -genmask too without success
route add default 18.104.22.168
But is is still not going out ! I can't even ping 22.214.171.124. Note that in
Linux, I used the exact same commands (though the syntax varies a big) and it
I was wondering if you guys had any idea about how to fix this configuration
Just for info, here is a shorten output from Linux routing table:
126.96.36.199 188.8.131.52 255.255.255.255 UGH eth0
0.0.0.0 184.108.40.206 0.0.0.0 UG eth0
I apologize if this is not very understandable, it is quite complicated to
explain in English which is not my birth language.
Thanks in advance.
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