ip_forwarding / gateway

Hello,

I am building a network of Linux boxes running a small self-made Linux. One
of these boxes is setup as a dial-in server for the network. I have the
dial-in part up and running, but have difficulties configuring the network
such that I can reach the Linux boxes from out of the network.

This is my setup:

92.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth ---> 192.168.5.3
etc.

My dial-in server has ip address 192.168.2.2 on the ppp connection and
192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
Ip_forwarding is turned on the dial-in server.

Using the pc with IP address 192.168.2.1, I am able to ping the Linux
dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
up. When I ping these boxes, I can see the lights of the Ethernet cards
flicker, but the ping requests time out.

Am I overlooking something? Any help is greatly appreciated.

Regards,
Whinyan.

Hello,

Whinyan a écrit :
>
> 92.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
> server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth ---> 192.168.5.3
> etc.
>
> My dial-in server has ip address 192.168.2.2 on the ppp connection and
> 192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
> Ip_forwarding is turned on the dial-in server.
>
> Using the pc with IP address 192.168.2.1, I am able to ping the Linux
> dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
> However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
> up. When I ping these boxes, I can see the lights of the Ethernet cards
> flicker, but the ping requests time out.

Do the hosts in the 192.168.5.x network have a route to 192.168.2.x (or
a default route) via gateway 192.168.5.1 ?

Pascal Hambourg wrote:
> Hello,
>
> Whinyan a écrit :
>
>>
>> 92.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
>> server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth --->
>> 192.168.5.3
>> etc.
>>
>> My dial-in server has ip address 192.168.2.2 on the ppp connection and
>> 192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
>> Ip_forwarding is turned on the dial-in server.
>>
>> Using the pc with IP address 192.168.2.1, I am able to ping the Linux
>> dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
>> However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
>> up. When I ping these boxes, I can see the lights of the Ethernet cards
>> flicker, but the ping requests time out.
>
>
> Do the hosts in the 192.168.5.x network have a route to 192.168.2.x (or
> a default route) via gateway 192.168.5.1 ?

Yes, they do have a route to 192.168.2.x via gateway 192.168.5.1.

Whinyan <(E-Mail Removed)> wrote:
> Hello,

> I am building a network of Linux boxes running a small self-made Linux. One
> of these boxes is setup as a dial-in server for the network. I have the
> dial-in part up and running, but have difficulties configuring the network
> such that I can reach the Linux boxes from out of the network.

> This is my setup:

> 192.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
> server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth ---> 192.168.5.3
> etc.

> My dial-in server has ip address 192.168.2.2 on the ppp connection and
> 192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
> Ip_forwarding is turned on the dial-in server.

> Using the pc with IP address 192.168.2.1, I am able to ping the Linux
> dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
> However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
> up. When I ping these boxes, I can see the lights of the Ethernet cards
> flicker, but the ping requests time out.

> Am I overlooking something? Any help is greatly appreciated.

Maybe the pppd proxyarp option?

--
Clifford Kite

Clifford Kite wrote:
> Whinyan <(E-Mail Removed)> wrote:
>> This is my setup:
>
>> 192.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
>> server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth ---> 192.168.5.3
>> etc.
>
>> My dial-in server has ip address 192.168.2.2 on the ppp connection and
>> 192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
>> Ip_forwarding is turned on the dial-in server.
>
>> Using the pc with IP address 192.168.2.1, I am able to ping the Linux
>> dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
>> However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
>> up. When I ping these boxes, I can see the lights of the Ethernet cards
>> flicker, but the ping requests time out.
>
>> Am I overlooking something? Any help is greatly appreciated.
>
> Maybe the pppd proxyarp option?

Perhaps. Perhaps routing weirdness on 192.168.5.2. Perhaps both. A
drawing that clearly labeled interfaces and hosts would be useful, along
with the routing table on the host with the interface labeled
192.168.5.2. An IP address is associated with an interface, not a host.
The distinction matters when you are dealing with hosts with more than
one interface.

Allen McIntosh wrote:

[clip]
> An IP address is associated with an interface, not a host.
> The distinction matters when you are dealing with hosts with more than
> one interface.

This is simply not true on Linux which uses the "so-called" WeakES
model.

The IP's most certainly do _belong_ to the the host and not the nic.
That's why a multihomed Linux host will gladly respond to any
assigned IP regardless on which nic it arrives.

It can make life very exciting ;-)

prg

Whinyan <(E-Mail Removed)> writes:

> Pascal Hambourg wrote:
> > Hello,
> > Whinyan a écrit :
> >
> >>
> >> 92.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
> >> server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth --->
> >> 192.168.5.3
> >> etc.
> >>
> >> My dial-in server has ip address 192.168.2.2 on the ppp connection and
> >> 192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
> >> Ip_forwarding is turned on the dial-in server.
> >>
> >> Using the pc with IP address 192.168.2.1, I am able to ping the Linux
> >> dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
> >> However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
> >> up. When I ping these boxes, I can see the lights of the Ethernet cards
> >> flicker, but the ping requests time out.
> > Do the hosts in the 192.168.5.x network have a route to 192.168.2.x
> > (or a default route) via gateway 192.168.5.1 ?
>
> Yes, they do have a route to 192.168.2.x via gateway 192.168.5.1.

I'd still wonder about the routing tables... maybe a wrong netmask?

You could try running wireshark on your gateway machine to see what
packets are going where.
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
New Mexico State University http://www.cs.nmsu.edu/~pfeiffer

Clifford Kite <(E-Mail Removed)> wrote:
> Whinyan <(E-Mail Removed)> wrote:
>> Hello,

>> I am building a network of Linux boxes running a small self-made Linux. One
>> of these boxes is setup as a dial-in server for the network. I have the
>> dial-in part up and running, but have difficulties configuring the network
>> such that I can reach the Linux boxes from out of the network.

>> This is my setup:

>> 192.168.2.1 <---ppp---> 192.168.2.2 <---ip_forwarding on the dial-in
>> server---> 192.168.5.1 <--- eth ---> 192.168.5.2 <--- eth ---> 192.168.5.3
>> etc.

>> My dial-in server has ip address 192.168.2.2 on the ppp connection and
>> 192.168.5.1 on the eth connection. 192.168.5.x is the Linux network.
>> Ip_forwarding is turned on the dial-in server.

>> Using the pc with IP address 192.168.2.1, I am able to ping the Linux
>> dial-in server on both its IP addresses (192.168.2.2 and 192.168.5.1).
>> However, I cannot reach the Linux boxes with IP addresses 192.168.5.2 and
>> up. When I ping these boxes, I can see the lights of the Ethernet cards
>> flicker, but the ping requests time out.

>> Am I overlooking something? Any help is greatly appreciated.

> Maybe the pppd proxyarp option?

Duh! I belatedly realized that this option alone isn't enough, assuming
the server LAN is 192.168.5.0/24 or similar. The dialed-in must also
use an unassigned IP address belonging to the server LAN on it's end
of the PPP link. If you do this, and have the right routing, then the
dialed-in should be able to reach the LAN hosts. You also should be
able to use 192.168.5.1 as the server's PPP IP address.

--
Clifford Kite