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RE: IP_alias under Red Hat
Moussa,
What are your routes on the Router and Dial-up Server? If you do not setup
the correct routes, obviously packets will not move.
It seems from your netplan that you are allocating the same IP block of
your Dial-up server and router to the dial-in clients. If this is the
case, the router will try to reach them directly, without sending the
packets first to the dial-in server (It thinks they are on the same
subnet).
Does ifconfig show that your alias IP on the dial-in server really has the
correct netmask? Check by doing ifconfig.
You will need to change you IP address allocation plan, and of course,
re-do your routing table.
----------------------------------------------
Sunday A. Folayan
General Data Engineering Services Ltd [SKANNET]
18b, Oshin Rd, Kongi Bodija Ibadan, Nigeria
Email: sfolayan at skannet.com.ng
Voice: +234-2-8105156 Fax: +234-2-8105156x221
-------
We accomplish in proportion to what we attempt
On Thu, 16 Jan 2003, Moussa Bagayoko wrote:
> Date: Thu, 16 Jan 2003 16:54:09 -0000
> From: Moussa Bagayoko <moussa at afribone.net.ml>
> To: Brian Candler <B.Candler at pobox.com>
> Cc: Mark Tinka <mtinka at africaonline.co.ug>, afnog at afnog.org
> Subject: RE: IP_alias under Red Hat
>
> Hi Brian
> You didn't understand very much. let me explain the problem with schemes. I
> have the following situations
> ppp link ethernet link
> client------------------dial up-----------------------router------>internet
> server R
>
> The dial up server has two IP address
> eth0 216.252.179.180.3 mask 255.255.255.128
> eth0:0 216.252.179.10 mask 255.255.255.128
>
> The default gw on the dial up server is 216.252.180.1 (the router R that has
> 216.252.179.1 as IP_alias).
>
> When client arrive with IP in the same bloc of eth0 e.g 216.252.180.11 there
> is no problem; all is right.
> So in the case where client has ip in the same bloc of eth0:0 e.g.
> 216.252.179.123 he cannot do anything outiside the dialserver. That's a
> problem.
>
> I don't no whether the problem come from the dial up server or the router R
> even it has ip address in both ip bloc.
>
> Thanks for your help
> Moussa BAGAYOKO
>
> > -----Message d'origine-----
> > De : owner-afnog at afnog.org [mailto:owner-afnog at afnog.org]De la part de
> > Brian Candler
> > Envoye : mercredi 15 janvier 2003 15:26
> > A : Moussa Bagayoko
> > Cc : Mark Tinka; afnog at afnog.org
> > Objet : Re: IP_alias under Red Hat
> >
> >
> > On Wed, Jan 15, 2003 at 12:56:48PM -0000, Moussa Bagayoko wrote:
> > > Thank for your quick response. I tried with eth0:0 and eth0:eth0.
> > > Actually the alias is ok with . All two address is reachable trough
> > > internet. So I'm using this machine as modem server and some client get
> > > connected with ip adress in the server ip alias bloc and they
> > can do nothing
> > > outside the server. But they can ping all two server ip
> > address. If they get
> > > connected with ip in the server primary ip bloc, all is right.
> >
> > I'm not sure exactly what you mean here.
> >
> > You can't give the same IP address to both the dial-in server and the
> > client:
> >
> > 10.0.0.1 and
> > modem link 10.0.0.2
> > client - - - - - - - - - dial-up -----------------R---> Internet
> > 10.0.0.2 server
> >
> > This simply won't work. When an inbound packet arrives from the
> > Internet to
> > 10.0.0.2, it will be delivered to the dial-up server (which says "10.0.0.2
> > is one of my own IP addresses, this packet is for me") and it won't be
> > forwarded down the modem link.
> >
> > So the next thing you might try is to remove 10.0.0.2 as an alias:
> >
> > modem link 10.0.0.1
> > client - - - - - - - - - dial-up -----------------R---> Internet
> > 10.0.0.2 server
> >
> > The problem here is that when a machine on the Internet tries to send a
> > packet to 10.0.0.2, it will get as far as the router R. R will try to send
> > an ARP packet for 10.0.0.2, but nobody will respond. So the
> > packet won't be
> > delivered.
> >
> > You have two solutions:
> >
> > (1) Put a static route on router R,
> >
> > ip route 10.0.0.2 255.255.255.255 10.0.0.1
> >
> > (note: if your dial-up server has more than one phone line then you
> > should allocate a block of IPs, which is in a different subnet, and
> > use that as your dialup pool)
> >
> > (2) Enable 'proxy-ARP' on the dial-up server for 10.0.0.2. Then, when
> > router R ARPs for 10.0.0.2, the dial-up server will respond saying
> > "yes that's me". R will send the packet over the ethernet to that
> > MAC address. When R receives the packet, it will forward it using its
> > own forwarding table.
> >
> > With Linux pppd, you could configure than easily: something like this
> >
> > [/etc/ppp/options.ttyS0]
> > :10.0.0.2 proxyarp
> >
> > With multiple phone-lines you write a separate options file with
> > a different
> > IP address for each line.
> >
> > If I have misunderstood your problem - then a diagram like one of
> > the above
> > would be very helpful in trying to understand what you're doing.
> >
> > Regards,
> >
> > Brian.
> >
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>
>
>
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