Can't route IP across eth0/ppp0 Linux gateway???

Can't route IP across eth0/ppp0 Linux gateway???

Post by David Lechny » Wed, 09 Apr 1997 04:00:00



Hey folks, here's the dilemma.  Pardon any errors in syntax, but it's a
recent dive for me into Linux ;-)

The dry details:
Linux Slackware 96
My Network:  x.y.z.152 - x.y.z.159
My Linux Box Ethernet Port:  x.y.z.153
My Linux Box PPP Port:  x.y.z.149
Sample Host on my network:  x.y.z.154
All are subnet mask 255.255.255.248

Connected via pppd to another network:
The Linux PPP connection on their end:  x.y.z.146
The Linux box is connected to their network, which includes a router.
The router (x.y.z.129) connectes to a 56k access line
Their subnet (except their Linux box of 255.255.255.248) is
255.255.255.240

My Linux box can ping anywhere just fine
My "Sample Host" can ping my Linux PPP connection and my Linux Ethernet
connection just fine
My "Sample Host" CANNOT ping past my Linux PPP connection and has no
connectivity.

Why is it isolated?  I would assume that IP is not routable across PPP
however the Linux box on the other network is routing IP across PPP
to/from me just fine.  I am using routed -s -g with default routes.  I'm
highly suspicious that it's a routing issue on my end, either routed is
the wrong command to use
Netstat -rn shows:
x.y.z.146   netmask 255.255.255.255 (it's ppp so only one host allowed),
gateway via my ppp0
x.y.z.152 (-net) netmask 255.255.255.248, gateway via my ethernet port
to my local network
default route is x.y.z.146

route shows that I have a metric of infinity to the first two routes,
even if I kill the routed, manually delete all routes, and start routed
again.  

1.  Is this related to the different subnet masks? (I don't believe so)
2.  Is my routing table incorrect, and why doesn't the default route
allow my hosts to ping past my Linux box?
3.  Should I be using gated rather than routed?

Thanks much,

David Lechnyr

------------------------
Opinions expressed do not necessarily reflect those of my employer or
it's affiliates.

 
 
 

Can't route IP across eth0/ppp0 Linux gateway???

Post by Jason K. Fritch » Thu, 10 Apr 1997 04:00:00


I believe the problem here is that IP Forwarding/Gatewaying is not
compiled into the kernel. Go over the kernel settings and if that option
is not set, then add it and do a recompile.


>Hey folks, here's the dilemma.  Pardon any errors in syntax, but it's a
>recent dive for me into Linux ;-)

>Why is it isolated?  I would assume that IP is not routable across PPP
>however the Linux box on the other network is routing IP across PPP
>to/from me just fine.  I am using routed -s -g with default routes.  I'm
>highly suspicious that it's a routing issue on my end, either routed is
>the wrong command to use
>Netstat -rn shows:
>x.y.z.146   netmask 255.255.255.255 (it's ppp so only one host allowed),
>gateway via my ppp0
>x.y.z.152 (-net) netmask 255.255.255.248, gateway via my ethernet port
>to my local network
>default route is x.y.z.146

--
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http://www.calweb.com/~fritcher/                              916-641-9320
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 ftp://ftp.calweb.com/users/f/fritcher/fritcher.key

 
 
 

Can't route IP across eth0/ppp0 Linux gateway???

Post by Paul Matthew » Mon, 14 Apr 1997 04:00:00



> My Network:  x.y.z.152 - x.y.z.159
> My Linux Box Ethernet Port:  x.y.z.153
> My Linux Box PPP Port:  x.y.z.149
> Sample Host on my network:  x.y.z.154
> All are subnet mask 255.255.255.248

> Connected via pppd to another network:
> The Linux PPP connection on their end:  x.y.z.146
> The Linux box is connected to their network, which includes a router.
> The router (x.y.z.129) connectes to a 56k access line
> Their subnet (except their Linux box of 255.255.255.248) is
> 255.255.255.240

> My Linux box can ping anywhere just fine
> My "Sample Host" can ping my Linux PPP connection and my Linux Ethernet
> connection just fine
> My "Sample Host" CANNOT ping past my Linux PPP connection and has no
> connectivity.

> Why is it isolated?

Are you sure that IP FORWARDING was configured into your Linux kernel?
It's easy to make sure:  

        head -2 /proc/net/snmp

You should see something like:

Ip: Forwarding DefaultTTL InReceives InHdrErrors InAddrErrors
ForwDatagrams InUnknownProtos InDiscards InDelivers OutRequests
OutDiscards OutNoRoutes ReasmTimeout ReasmReqds ReasmOKs ReasmFails
FragOKs FragFails FragCreates
Ip: 1 64 23385 10 0 0 0 0 9561 20378 0 3 0 66 23 0 0 0 9523

The first param is IP FWD, and it should be a 1.  You can also see the
packets sent out and packets received.

One thing that surprised me in earlier Linux pppd code was that the ppp0
interface and the eth0 interface can be the same.  For whatever reason,
earlier pppd's would not work correctly as a "router" if these two IP
numbers were different.  Also, if you are giving the kernel gateway
entry, don't.  Use the pppd parameter default gateway and let pppd take
care of gateway entries.

You might want to post this type of question in comp.protocols.ppp.

--
Regards,
Paul Matthews

 
 
 

1. AUTOPPP ppp0 vs eth0 ip routing

I cant get my linux mandrake 7.1 to route between ppp0 and eth0
Can sombody please help me.
Here is the story.

1) eth0 is running OK with a static ip 192.168.127.5 mask 255.255.255.0
2) Iv got mgetty started from the inittab
3) /etc/mgetty+sendfax/login.config has
/AutoPPP/ - a_ppp /usr/sbin/pppd noauth

Now connecting to the Linux machine works fine.
But it seems like pppd has stolen the address 192.168.127.5
making it possible to ping it from the calling ppp client

So in my opinion ppp0 should have its own address on its own subnet,
something like 192.168.65.1 on 192.168.65.0 and mask 255.255.255.0
Q1) Is this correct?????
If this is correct. Propobly i would have to add something in the file
/etc/mgetty+sendfax/login.config      in line
/AutoPPP/ - a_ppp /usr/sbin/pppd noauth
Q2) What do I write ??? How is this done?????

Then I want the server to route all the incoming connections to our LAN
meaning routes from 192.168.65.1 to 192.169.127.0.

So when I connect my client to the PPP server it results in getting access
to our LANs
pop3 server on 192.168.127.4
sql1 server on 192.168.127.4
sql2 server on 192.168.127.3
and all other machinse on this subnet

I think I would have to add a route to the route table on the Linux machine
Q3) How do i do this.???? with the "route add" command or something in the
pppd command????

Any help here are welkom since I novice to Linux and IP routing.
Please help me.


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