Anton J Aylward recently wrote:
>
> At 08:41 AM 20/02/97 -0500, Richard Brackett wrote:
>
> >I don't believe that you are going to be able to make that configuration
> work.
> >How is TCP/IP supposed to choose
> >which adapter to use when talking to that subnet? Any multi-adapter
> configuration
> > I've seen or implemented needed
> >two different subnets to work. I've done this under various unix flavors,
> Netware, and NT.
> >Most OS's will allow
> >multiple same-subnet addresses to a single card, but not two different
> cards.
> >
> >Others may have different experiences and I'd be interested in hearing
> from anyone with more
> >depth of knowledge on the subject.
> >
> >Richard
> >
> >>>> Ruben Sajnovetzky <ruben @
is .
com .
ar> 02/19/97 11:59am >>>
> >+ I wants to configure the two ATM interfaces using same a subnet
> >+ address(192.11.214.0) on a SGI workstation, for example, one is
> >192.11.214.10
> >+ and another is 192.11.214.11. But I found if I assigned the two ATM
> interfaces
> >+ into same a subnet, the IRIX system couldn't work correctly. If I
> assiged the
> >+ two ATM interfaces into two different subnet(ex: 192.11.214.10 and
> >+ 192.11.215.20), our IRIX system could work correctly. Do you know that two
> >+ network interfaces(such as ATM, ethernet or FDDI) in a UNIX machine can be
> >+ assigned into same a subnet? If can, how should I configure?
>
> 100% correct. So lets cheat.
>
> First I'm going to pick the network address on the class C subnet you
> describe.
> I'm not going to use 10 and 11, I'm going to use 10 and (just to be
> preposterous)
> 255-10 = 245, which was my old house number.
>
> Now I'm going to squint very hard and make the class C go away.
> With this squint, you no longer have a 24 bit subnet mask, 255.255.255.0
> (or ff.ff.ff.00) but instead a 26 bit mask (ff.ff.ff.80).
>
> OK, I told you I was going to cheat.
> >From the point of view of this machine, its on TWO subnets, each of which
> is half a class C. This is because when you did and ifconfig on each of the
> ports you did the appropriate mask as well.
>
> But that's only for this machine. All the other single ported machines
> on the class C don't suffer from this.
>
> I do say suffer. As Richard Brackett said, how are you going to make this
> work?
> What good will it do you? Are you trying to do load balancing? Split the
> load between
> two cards? Well this isn't going to do that. If that's your problem you
> need to
> figured out WHY you need more bandwidth. Run a snooper and see all the
> junk you're
> putting out. Turn off rwhod, and all those other noisy protocols like NIS
> and NFS. ;-)
>
> Putting on my consulting hat for a moment, lets ask two questions:
>
> 1. What are you trying to do?
> Oh yes, put two cards on the same machine on the same subnet.
>
> 2. What are you trying to ACHEIVE? What is your ENDPOINT OBJECTIVE?
>
> Sorry that's three. Assume the last two are different ways of asking the
> same thing.
>
> OBTW: Some RFC and hence some routers and IP stacks may not take kindly to
> this
> chopping of subnets on non-8-bit boundaries, CIDR not withstanding.
> Some may say that all of the subnet 0 part simply isn't accessible.
> Your milage may vary. All I can say is that it has worked for me.
>
> --------------------------------------------------------------------------
> Anton J Aylward | Security is not something that comes in
> The Strahn & Strachan Group Inc | a self-contained box. It is an attribute
> Information Security Consultants | of how you do business and as such
> Voice: (416) 494-8661 | needs to be managed carefully.
> Fax: (416) 494-8803 | - Karen Goertzel, Wang Federal Inc.
>
I don't think this will help you unless the single NIC is overloaded in the
first place. Just by adding a second NIC will only help if the problem
is the NIC throughput. It's not going to help if the problem is network
bandwidth.
/Jim/
--
James P. Egan | Jim .
Egan @
iai .
com
Integrated Architectures, Inc. | http://www.iai.com
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