RACKLEY@MSSTATE.BITNET (Mike Rackley) (10/02/88)
BACKGROUND: We are implementing a campus-wide network which will be a bridged ethernet supporting TCP/IP. The only router in the network is a P4200 which is our SURANET gateway. We have a class B internet address, 130.18. It was suggested that we assign our campus IP addresses in a "subnetted fashion", even though we will not be using routers to physically subdivide our network. Typically, we will allocate one subnet per building, with a MAC level bridge connecting each building to the backbone. QUESTIONS: Does the suggestion that we assign IP addresses in a "subnetted fashion" imply that we should also assign a subnet mask of other than 255.255.0.0? If we do this, it means that the gateway for most hosts on our campus net will be on a different subnet than the host itself. Is this legal? Even if it is legal, is this really what we want to do? This would mean that all intra-campus traffic between two different "pseudo-subnets" would have to pass through the one P4200, even though normal ARP routing could be used.
casey@admin.cognet.ucla.edu (Casey Leedom) (10/06/88)
In article <8810031020.AA02610@ucbvax.Berkeley.EDU> RACKLEY@MSSTATE.BITNET (Mike Rackley) writes: > Does the suggestion that we assign IP addresses in a "subnetted fashion" > imply that we should also assign a subnet mask of other than 255.255.0.0? The suggestion that you assign your IP addresses in a ``subnet-like'' fashion was probably made to make switching over to subnets in the future easier. It doesn't hurt you to assign your addresses in a subnet-like fashion - say by building or other organizational or geographic assignment - and it makes dividing the administration of your net (ala BIND subdomains for instance) and monitoring your net easier. We assigned buildings unique third byte IP addresses at Lawrence Livermore National Lab for just those reasons even though LLNL isn't subnetted. I'd take the suggestion if I were you. Casey
ron@ron.rutgers.edu (Ron Natalie) (10/06/88)
If your campus is connected together by datalink bridges rather than routers, you are not really subnetting. You are just imposing a scheme for assigning numbers. Leave the hosts thinking they are using an unsubnetted class B network (which is what they are doing). You can still assign the more significant byte to be the building number and the least significant one to be the host number. That way if you ever do get smart and get routers, you will already be ready to subnet. You will avoid having to renumber everything. -Ron
sean@cadre.dsl.PITTSBURGH.EDU (Sean McLinden) (10/07/88)
In article <Oct.5.17.25.28.1988.245@ron.rutgers.edu> ron@ron.rutgers.edu (Ron Natalie) writes: >If your campus is connected together by datalink bridges rather than >routers, you are not really subnetting. You are just imposing a scheme >for assigning numbers. Unless, of couse, within these buildings you have hosts which are attached to multiple networks (such as a local NFS net or PC net). Then you'll want to run with subnetworks (in fact, you almost have to). >Leave the hosts thinking they are using an unsubnetted >class B network (which is what they are doing). You can still assign the >more significant byte to be the building number and the least significant >one to be the host number. That way if you ever do get smart and get >routers, you will already be ready to subnet. You will avoid having >to renumber everything. We have a similar thing at the University of Pittsburgh. The problems start when someone wants to run subnets which will allow all hosts on any net to talk to each other. My personal experience echoes Ron's suggestion. If you even think that you MIGHT someday want to subnet somewhere, plan for it now. It really does make life easier in the future. Sean McLinden
08071TCP@MSU.BITNET (Doug Nelson) (10/08/88)
Mike Rackley asks: >Does the suggestion that we assign IP addresses in a "subnetted fashion" >imply that we should also assign a subnet mask of other than 255.255.0.0? No, your subnet mask should be 255.255.0.0. You're just facilitating a future migration to real subnetting, if/when needed. Doug Nelson Computer Laboratory Michigan State University