Date: Fri, 16 Jun 2000 21:17:13 -0400 (EDT) From: Colin <cwass99@home.com> To: Mike Smith <msmith@FreeBSD.ORG> Cc: hackers@FreeBSD.ORG, "Marinos J . Yannikos" <mjy@pobox.com>, nino@inode.at Subject: Re: routing bug(?) persists (PR 16318) Message-ID: <XFMail.000616211713.cwass99@home.com> In-Reply-To: <200006151644.JAA02187@mass.osd.bsdi.com>
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What you're doing here is generally referred to as multi-netting. When
you're wandering through the references, use that as a starting point.
Multi-netting is certainly valid, when implemented correctly. I would
definately echo the sentiment elsewhere in this thread that you and your
ISP are using a broken implementation, and I honestly see no reason that what
you're doing should work at all. Effectively you're telling your system that
the way to connect to networks that it's address is not part of is to send a
message to a host that is on a network it's address is not part of. It's a
networking catch-22 ;) Either you or your ISP needs to alias the adapter on
this set of subnets, and if you're not the only person on this multi-netted
section, it really should be them.
This is definately a routing bug, but it's in Win and Linux if they alloow
this with no error.
Cheers,
Colin
On 15-Jun-00 Mike Smith wrote:
>> On Thu, Jun 15, 2000 at 07:33:36AM -0700, Mike Smith wrote:
>> > [mjy]
>> > > ifconfig_vr0="195.58.183.77 netmask 255.255.255.248"
>> > > static_routes="0 1"
>> > > route_0="-net 195.58.161.96 -netmask 255.255.255.240 -iface vr0"
>> > > route_1="default 195.58.161.97"
>> >
>> > The above network configuration is incorrect - you need a gateway that is
>> > directly reachable.
>>
>> The gateway is physically connected to the same network, the physical
>> network
>> contains 2 (or more) distinct subnets.
>
> Correct. You are not, however, logically connected to the network on
> which your gateway resides.
>
>> > If you want to use the above default route, you need
>> > to give your machine an address on the same network as your gateway, most
>> > trivially by aliasing it onto the vr0 interface.
>>
>> I don't see why that should be necessary - my ISP doesn't either, since he'd
>> have to part with another IP address. My ISP claims and I've verified that
>> the configuration above works trivially under Linux and Windows NT, and
>> as far as I can tell, the submitted patch does nothing more than to allow
>> the specified interface to be taken into consideration when "connectedness"
>> is determined (i.e. it allows the gateway to be in a different subnet as
>> long
>> as it is physically connected).
>
> I would suggest you go find an introductory IP networking book, and get
> two copies (one for yourself, and one for your ISP). What you're trying
> to do is a fundamental violation of the way that IP routing works, and
> this is what the network stack is trying to tell you.
>
> The fundamental problem is that when you send a datagram to your gateway,
> you can't put a valid return address on it (because you don't have an
> appearance on its network). If you've put the interface's real address
> in the datagram, you'll never get a reply because your gateway has no
> idea how to route back to you.
>
> If you can't get an IP on your gateway's network, alias another address on
> your private network onto the gateway system's interface and use that as
> your default route. If your gateway is too lame to support multiple
> addresses on an interface, use another system that does have a real
> appearance on the gateway's network to route for you.
>
> And read that book - it'll save you a lot of agony in the future.
>
>
> --
> \\ Give a man a fish, and you feed him for a day. \\ Mike Smith
> \\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org
> \\ and he'll hate you for a lifetime. \\ msmith@cdrom.com
>
>
>
>
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