PPP problem

PPP problem

Post by NE Regional Health Syste » Thu, 31 Aug 2000 04:00:00



I would like to setup a couple linux boxes to handle my remote
communications between my two different networks.  Machine A is a Redhat 6.2
server with one NIC manually configerd as such:
IP address 192.168.1.4
Netmask 255.255.255.0

/etc/ppp/options
lock
require-chap
require-pap
-detach
asyncmap 0
crtscts
proxyarp
192.168.4.1:192.168.4.2

Machine B is setup up with FloppyFW and is configured as such:
IP address 192.168.3.1
Netmask 255.255.255.0

My problem is this.  I am using machine B to dial on demand to machine A and
start a ppp session.  I can connect ok and start my ppp session.  Machine A
is assigning 192.168.4.2 address to the ppp0 interface on machine B and
assigning its own ppp0 interface the address 192.168.1.4.  Can anyone tell
me why it is assigning the ip address of its own nic to the ppp0 interface.
I am also wanting to know with this setup will my two networks be able to
communicate both ways with each other?

thanks for your help

 
 
 

PPP problem

Post by Clifford Kit » Sat, 02 Sep 2000 22:23:06



Quote:> I would like to setup a couple linux boxes to handle my remote
> communications between my two different networks.  Machine A is
> a Redhat 6.2 server with one NIC manually configerd as such: IP
> address 192.168.1.4 Netmask 255.255.255.0
> /etc/ppp/options
> lock
> require-chap
> require-pap
> -detach
> asyncmap 0
> crtscts
> proxyarp
> 192.168.4.1:192.168.4.2
> Machine B is setup up with FloppyFW and is configured as such:
> IP address 192.168.3.1
> Netmask 255.255.255.0

Don't know FloppyFW but I assume that the IP address is for an interface
on machine B attached to a local network.

Quote:> My problem is this.  I am using machine B to dial on demand to
> machine A and start a ppp session.  I can connect ok and start my
> ppp session.  Machine A is assigning 192.168.4.2 address to the
> ppp0 interface on machine B and assigning its own ppp0 interface
> the address 192.168.1.4.  Can anyone tell me why it is assigning
> the ip address of its own nic to the ppp0 interface.

You need to add the pppd noipdefault option to B, or, perhaps, the
ipcp-accept-local option.  Read about these in "man pppd."

Quote:> I am also wanting to know with this setup will my two networks be
> able to communicate both ways with each other?

No.  The proxyarp option requires that machine A have a interface on
the local network and that machine B use an IP address belonging to
that network for the PPP connection.  That is, B has to use an IP
address for the PPP connection that is on 192.168.1.0/24.  The PPP
IP address of B must be a gateway for network routing on A to the
network of B, or it could be the default gateway IP address on A if
there is no need for a default route elsewhere.  Machine A must also
have IP forwarding compiled into the kernel and turned on.

The same things must be true when "A" and "B" are swapped in the
preceding paragraph and the network is changed to 192.168.3.0/24.

An alternative is to configure all machines on each local network,
except for the network's PPP host, so that the PPP host (A or B)
is the gateway for a network route to the local network of the other
PPP host.  IP forwarding would still be necessary for the PPP hosts
but not the proxyarp option.  As in the previous suggestion, each PPP
host would need to be configured so that the IP address of the other
PPP host is the gateway for a network route to the local network of
the other PPP host

A third alternative is to run routing daemons, but I can't help
there.

--

/* If this answer is broken then you get to keep both pieces. */

 
 
 

PPP problem

Post by James Carlso » Sun, 03 Sep 2000 02:17:10



Quote:> My problem is this.  I am using machine B to dial on demand to machine A and
> start a ppp session.  I can connect ok and start my ppp session.  Machine A
> is assigning 192.168.4.2 address to the ppp0 interface on machine B and
> assigning its own ppp0 interface the address 192.168.1.4.  Can anyone tell
> me why it is assigning the ip address of its own nic to the ppp0 interface.

That's the default; use "nodefaultip" if you don't want it to do that.
(Why is this a problem?  Reusing IP addresses where possible is a good
thing; it conserves IP address space.)

Quote:> I am also wanting to know with this setup will my two networks be able to
> communicate both ways with each other?

Proxy arps aren't normally used to set up links between two networks.
It doesn't make much sense to do that.  It also doesn't make sense to
number the link -- just let the default IP addressing do its work.

In any event, you'll need to turn on IP forwarding on both hosts and
set up either static routes or a routing protocol in order to get the
two networks to talk.  This isn't a PPP issue; it's a routing issue.

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