Subject: Re: arp.
To: None <firstname.lastname@example.org>
From: Andy V. Oleynik <email@example.com>
Date: 04/06/1999 14:29:30
"Crist J. Clark" wrote:
> Andy V. Oleynik wrote,
> [Charset koi8-r unsupported, filtering to ASCII...]
> > andrea wrote:
> > > I have to add a gateway to my net for experimental reasons.
> > > Actually there are : a main-router that works as interface to the Internet,
> > > and some hosts on my sub net.
> > >
> > > Internet-----MyRouter----MySubNet
> > >
> > > NOw i need to configure one host of MYSubNet to act as a gatway for the
> > > secondary subnet.
> > > Both the 1SubNet and 2 SubNEt share the same ip-range.
> > >
> > > Internet-----MyRouter----MySubNet-----My2SubNet
> > As I understood U have smth like this :
> > Internet-----MyRouter----MySubNet
> > |----2ndRouter-----My2SubNet
I mean 2ndrouter is on MySubNet, sorrey for unclearity:)
> > Then U have to cut My2SubNet from ur MySubNet and configure
> > routes to appropriate subnets on appropriate hosts. As long as ur 2ndsubnet
> > is part of ur mainsubnet the hosts from 2ndsubnet will be seen from internet
> > & wise a versa. U may need to run DNS for reverse zone of ur My2SubNet
> DNS has nothing really to do with this problem. I believe the original
I said "U may" not "U must". At least I run DNS for revzones of my subnets.
> poster is describing the following (this may be what the second poster
> meant to write, but proportional fonts, tab damage, or his character
> set wiped it out),
> > >
> > >
> > > All the sub.net have to be seen from the Internet so I'll need to add a
> > > route to MainRouter in order to route the Secondary Subnet.
> > > The problem is that i cannot change configuration of the mainroute,so i
> > >
> > in fact this isnt big problem as soon as U have properly configured
> > subnets:) . Correct me if I wrong.
> This is a problem. You are wrong. But back to the original poster, why
Sorrey Crist, but there is no need to connect 2nd router to 1st. If U have to
have 2nd subnet just insert 2nd NIC into 1st router and as I sad above
configure ur subnets (with appropriate routes on router off cause &
defaulterouter on hosts on subnets :).
> can you not change the configuration on the Primary Router? If this is
> your network, and you want to be able to do things like this, you need
> to be able to change the Primary Router configuration.
> To the second poster, when the Primary Router receives a packet
> destined for a machine on SubNet1 or SubNet2, since the Router
> believes all of those machines are still on its LAN, it will try to
> use the MAC address (layer 2) to send the packet directly to the
Is this true if 1strouter knows that a route to 2ndsubnet is throught 2ndrouter
on same subnet as 1strouter?
> machine. However, now this machine has been moved behind the Secondary
> Router. The Secondary Router is not listening for other machines'
why not if it's configured as gateway to 2ndsnet?
> packets at layer 2 (in a typical router setup), so it never gets the
> packet and never tries to forward it. It also would not respond to ARP
> calls by the Primary Router when it is looking for a machine on
> > > wonder if is possible to configure the new gateway to do a sort of "proxy
> > > arp" for my secondary Subnet.
> > > But arp-tables are system-wide so if i change arp entry to cacth request on
> > > PrimaryNet the 2subnet dont'works anymore.
> > > Is possible to catch arp request only on a single subnet,without broke any
> > > other subnet connected to the same host.?
> It is possible. But I am unaware of a tool to do this (which does not
> mean there is not one). Might you be better off building a 'new' net
> behind your Secondary Router? Say using NAT and a 10.0.0 subnet?
>  All you need to do on the router is add a route to Secondary
> Router for IPs on SubNet2. All you need is the address for the
> Secondary Router and a subnet mask.
>  The Secondary Router would not actually be doing routing in this
> case. It's acting more like a switch. You did not really tell us why
> you are doing this. Would getting a switch be a better option for you?
> Crist J. Clark firstname.lastname@example.org
WBW Andy V. Oleynik (When U work in virtual office
U have good chance to obtain virtual money ö%-)