How do I connect to PPP using DHCP
Meaghan
I have a Red Hat 6.2 server running DHCP and PPP. At the moment, we
manually give each of our Windows 95/98/2K clients a permanent IP
address, so that they can connect via a modem to our server using PPP.
Instead of this, we wanted our clients to be automatically assigned an
IP address by DHCP, as we already have DHCP running for our ethernet.
Is this possible? Can someone direct me as to how to do it, or where
I can go to find out?
Thanks for your help,
Meaghan
James Carlson
> I have a Red Hat 6.2 server running DHCP and PPP. At the moment, we
> manually give each of our Windows 95/98/2K clients a permanent IP
> address, so that they can connect via a modem to our server using PPP.
Assigning per-port addresses instead would probably be a much better
idea. Not only is it extremely simple to do, but it's logically
consistent -- you need only as many addresses as you have
communications links.
> Instead of this, we wanted our clients to be automatically assigned an
> IP address by DHCP, as we already have DHCP running for our ethernet.
Unless there's a compelling reason to avoid assigning one address per
port (and it's hard to think of one), I'd suggest reconsidering.
> Is this possible? Can someone direct me as to how to do it, or where
> I can go to find out?
It's possible only by hacking the sources for pppd. There's no IPCP
DHCP client built into pppd, nor any recent patches that I can find.
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James Knott
Usually, you'd configure on IP for each port, so that the assigned
address will depend on which port the user connects to. There's no
need to use DHCP.
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Roy Lauer
"James Knott" <the.lights.are....@home.com> wrote in message
news:undB7.64582$YL3.17...@news3.rdc1.on.home.com...
> Meaghan wrote:
>
> > Hi,
> >
> > I have a Red Hat 6.2 server running DHCP and PPP. At the moment, we
> > manually give each of our Windows 95/98/2K clients a permanent IP
> > address, so that they can connect via a modem to our server using PPP.
> >
> > Instead of this, we wanted our clients to be automatically assigned an
> > IP address by DHCP, as we already have DHCP running for our ethernet.
> >
> > Is this possible? Can someone direct me as to how to do it, or where
> > I can go to find out?
>
> Usually, you'd configure on IP for each port, so that the assigned
> address will depend on which port the user connects to. There's no
> need to use DHCP.
>
IP addresses allocation is done dynamically, you can not use this approach.
There is a true need for using a DHCP server.
The question is how to do that?
James Carlson
> When you're server is located in a network using DHCP, where all the
> IP addresses allocation is done dynamically, you can not use this approach.
That's not generally true. Most DHCP servers have administrative
mechanisms that allow you to declare one or more addresses as being
"statically allocated" or otherwise off-limits. Assuming your DHCP
server isn't lame, you just enter your per-port addresses into that
table.
> There is a true need for using a DHCP server.
> The question is how to do that?
With pppd, you don't. Anything that really requires this sort of
service is very likely to be a large installation serving hundreds of
PPP links, and is better served by commercial communications servers
than by freeware.
Again, you're free to hack pppd if you like, but I don't recommend it
in this particular case.
Michael Mueller
I am not aware of any patch for pppd to get an IP-address via DHCP
during the IPCP phase. You should not need it either.
Assign any dial-up interface (each copy of pppd running) a unique
ip-address. Configure pppd not to accept any local or remote IP from the
client but to insist on its own choice. This way you only need as many
IPs as you have dial-in lines. The clients will see the addresses as
dynamic because the resulting IP for it does depend upon which line it
did end up on.
Michael
James Knott
The PPP addresses have to be within the range specified by the sub net
mask. The DHCP server can be configured to not assign the addresses
used by ppp. For example your network is set to use the address range
of 192.168.1.0/24. You could assign addresses 192.168.1. 224 -
192.168.1.250 to PPP ports and limit the DHCP server to addresses in
the range of 192.168.1.1 -192.168.1.223. Is there some reason why your
DHCP server cannot be configured in this manner?
David Efflandt
I tried using DHCP to assign a remote IP address for a PPP connection on a
Cisco (2509?) router that was supposed to be able to do that. While the
router did get a proper IP from the DHCP server, and it appeared in the
ppp negotiations on the Linux box, Linux pppd didn't seem to know how to
use that like a normal dynamic IP. So I resorted to using a static IP for
each modem, and that works fine.
You could always use a different subnet for the remotes and masquerade
them on your LAN (the opposite direction from masqueding for an ISP), if
you cannot get your admin to assign static IP's for that purpose. But
then Windows networking might be problematic.
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Denis Mcmahon
>"James Knott" <the.lights.are....@home.com> wrote in message
>news:undB7.64582$YL3.17...@news3.rdc1.on.home.com...
>> Usually, you'd configure on IP for each port, so that the assigned
>> address will depend on which port the user connects to. There's no
>> need to use DHCP.
>>
>When you're server is located in a network using DHCP, where all the
>IP addresses allocation is done dynamically, you can not use this approach.
>There is a true need for using a DHCP server.
>The question is how to do that?
Reserve a range of addresses for static allocations in the dhcp
server, and use those.
Rgds
Denis
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