Re: [SLUG] Routing across ethernet and ppp?

[Kieran <kieran@nospam.ghost.dhs.org>]

Hi DaZZa, Jason,

Whilst what DaZZa said about having 139.x.x.x as the ppp0 address, I have
a similar setup to Jasons which works (although wether it is right or not
I dunno :-)).

Comp 1: Gateway
ppp0: 139.x.x.x
eth0: 203.x.x.169

Comp 2: 
eth0: 203.x.x.168 (why it is less? Was too lazy to change it around to 169
instead :-)).

On Comp 2 I set a default route for all packets to goto the gateway
203.x.x.169.  Unfortunately I can't remember the syntax off the top of my
head (machine 2 is down atm without a video card :-)) but I tihnk it goes
a little like this:
route add default gw 203.x.x.169

Then on Comp 1 I add a routing rule that states if anythign comes in to go
to 203.x.x.168, then I pass it out to eth0 where the machine will get it.
That rule goes like this:
route add -host 203.x.x.168 dev eth0

I believe that is all that is really needed (aside from ip-forward) to get
things flowing :-).

Would someone like to pick that apart and tell me a better way it could be
done?

Cheers,
Kieran

P.S. been a little late on following this thread, sorry for the late reply
and if it convers stuff already gone over before.


On Tue, 2 May 2000, DaZZa wrote:

> On Tue, 2 May 2000, Jason Lowe wrote:
> 
> > Computer 1:
> > * ppp0: 203.x.x.121 (Direct connection to Telstra Big Pond)
> > * eth0: 203.x.x.123
> 
> This is your first problem.
> 
> Without knowing your subnet masking {but assuming a standard class C mask
> of 255.255.255.0}, you have a single machine with two IP addresses on the
> same subnet but different interfaces. From memory, this will completely
> screw routing. The box won't know which interface to throw packets for the
> subnet out on.
> 
> > Computer 2:
> > * eth0: 203.x.x.122
> > 
> > The problem: How do I setup routing so that computer 2 can be seen on the
> > Internet?
> 
> You need to change your ppp0 IP address to the elstra assigned 139.x.x.x
> address.
> 
> So you end up with this.
> 
> Computer 1
> 
> ppp0	-	139.x.x.x {Telstra link
> eth0	-	203.x.x.1 {Your Ip range}
> 
> Computer 2
> 
> eth-	-	203.x.x.2 {Your IP range}.
> 
> > Computer 1 has a direct connection to the Internet and works fine. We are
> > running mail, web and squid to give all internal users access to the
> > Internet. Computer 2 cannot be seen from the Internet.
> >
> > * The ppp0 to telstra is 203.x.x.121 our end which is linked to teltra's
> > gateway of 139.x.x.x
> 
> Who assigned this address for your gateway? And what subnet mask is being
> used?
> 
> > * I can ping 139.x.x.x from Computer 1
> > * I cannot ping 139.x.x.x from Computer 2
> > * I have swapped over IP address on Computer 1 (ppp0) to that on Computer 2
> > (eth0) and manage to operate the direct connection correctly. This implies
> > that routing on Telstra's end to 203.x.x.12x is correct!
> > * Computer 2 can ping 203.x.x.121 and 203.x.x.123 on Computer 1 (They're on
> > the same network)
> 
> As they should - there's no routing involved - just a direct broadcast.
> However, with the two network adapters in the one machine on the same
> subnet thing, I wouldn't be surprised if this ping traffic was being
> directed out to the net as well as on the local subnet - at least as far
> as the Telstra link, anyway.
> 
> To say more, I'd need to know your entire setup - IP addresses complete,
> and subnet masks, dumps from ifconfig and route etc etc.
> 
> DaZZa
> 
> 
> 
> --
> SLUG - Sydney Linux Users Group Mailing List - http://www.slug.org.au
> To unsubscribe send email to slug-request@nospam.slug.org.au with
> unsubscribe in the text
> 

--
SLUG - Sydney Linux Users Group Mailing List - http://www.slug.org.au
To unsubscribe send email to slug-request@nospam.slug.org.au with
unsubscribe in the text