I thought G meant "the default gateway is on this interface".

It is "ip.forwarding" that enables the host to act as a gateway.

Think of if from the openbsd box's point of view, "I have a packet that I need to deliver so...."

(a) do I have any interface that IS that destination address, if so send to that interface (eg loopback messages, incoming messages to this host)

(b) do I have any interfaces on the same subnet (eg take netmask and apply to destination address and compare with interface.

(c) do I have a static route configured? If so send to appropriate interface

(d) if none of those, do I have a default route and on which interface?

(a) I not really understand
(b) None
(c) I don't have any static route which is all automatic done by openbsd.
(d) I have default route which is located on tun0 which is a virtual interface for pppoe.
Default 219.93.218.177 UG tun0
Thanks for your reply.

From www.linuxhomenetworking.com chapter 8 mentioned that if you have multipl interface with dhcp server, u need to add a router 255.255.255.255. IS it true ?
Thanks for oyur help.

Please post the output of:

OBTW, which TCP book did you get from the library?

rl0(External Interface), rl1(Internal)ral0 wireless.
This is routing table when i have no connection to the openbsd gateway. :
Destination Gateway Flags refs Use Mtu INterface
default 219.93.218.177 UGS 2 18802 - tun0
127.0.0.1 127.0.0.1 UH 0 2 33224 lo0
176.16.10/24 link#2 UC 0 0 - rl1
192.168.1/24 link#1 UC 1 0 - rl0
192.168.1.1 H.addrs UHLc 1 6 - rl0
192.168.2/24 link#3 UC 0 0 - ral0
219.93.218.177 60.48.0.0 UH 1 0 1472 tun0

I used some online book such as techbooksforfree/networking and tcpipguide.com.
By the way, why openbsd need to manually configurate route and freebsd doesn't need it ? Am i correct ?
A billion thanks for oyur help and merry christmans

I have add! default HISAddr in my /etc/ppp/pppoe.conf I don't know whether this is relavant but just an extra information.