[pptp-server] "proxyarp" or " route"

[Nick Blievers]

Hi,
    I'm not really sure what you are trying to achieve here, perhaps you could
clarify. When you say x.x.24.99 'dials up' the PoPToP server, do you really
mean using a modem? If so, and you are dialing up directly to the linux box,
you need to set up your routing and maybe the cisco filtering rules, and leave
PoPToP out of it.

    If you are connected to the same LAN, then what is stopping you accessing
the web directly?  Please clarify what you are trying to achieve as there are
several different different issues here, and then we can work on one at a
time.
    For clarification:
    NAT = Network Address Translation. On the 2.2 series kernel this is
achieved via IP Masquerading.
                A <---> B <----> C
    So, A can talk to C, seemingly directly, but C thinks the packets come
from B. This can be cool to use to allow access to the net from hosts with
private IPs.

    ARP = Address Resolution Protocol. This is used to translate an IP address
to a hardware address (usually an ethernet one) arp maintains a cache of
hardware addresses, although if a hardware address is not found, then arp
broadcasts a packet to every host on the ethernet requesting the owner of IP
address xxxx speak up and send its hardware address back. Proxying arp
requests means replying to arp requests for IP's other than your own.
    eg    A<--->B<--->C
    The AB link is non-ethernet (eg dial-up) and the BC link IS ethernet (say
100Mbit UTP in an office or something), then C will not necessarily know about
A, as A will never receive an ethernet broadcast (eg an arp request) from C.
However, B will, and B can be made into an arp proxy and answer the query on
A's behalf.
Or to put it another way proxyarp "will have the effect of making the peer
appear  to other systems to be on the local ethernet" (from the pppd man
page), so that is useful for using

    So, the long and the short of it is, get a ppp link to the server first
(either via dial-up or directly), and get THAT working, then work out whether
you need the rest. PPTP may not be the answer you need.


    Hope this (rather long winded) reply helps.


    Nick Blievers


Zhu Xiaofeng wrote:

> Hi everyone:
>
>    I setup PoPToP 1.0.0 on my Turbo linux 6.0 . My network configuration is
> following:
>
>          PoPToP server          cisco router
>           x.x.24.198   <-------->  x.x.24.1 <----> real Internet
>               |
>               |
>               |
>          win2000
>          x.x.24.99
>
> /etc/ppp/options
>
> debug
> name linux
> auth
> require-chap
> proxyarp
>
> /etc/pptpd.conf
>
> option /etc/ppp/options
> debug
> speed 115200
> localip x.x.24.220-229
> remoteip x.x.24.230-239
>
>  My idea is to let x.x.24.99 dial on x.x.24.198 via PPTP to access real
> Internet.
> All address are real IP addresses.I don't think it need NAT or IP MASQE .Is
> it OK?
> Should I do more configration on x.x.24.198 ?
>
>   When I dial up from x.x.24.99 to  x.x.24.198 ,win2000 get PPP client
> address x.x.24.230 and PPP
> server address is x.x.24.220 . Ping x.x.24.230 is not accessable but
> x.x.24.220 is accessable from other
> computer x.x.24.200 .I don't know much about "proxyarp",but I think it is
> x.x.24.230 that can be accessable.
> Why?
>
> xfzhu.
>
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