lr@cs.brown.edu (Luigi Rizzo) (05/11/91)
Hi there, we have the following configuration problem. This is our network structure (all Ethernet running TCP/IP): global internet | R | net1 ------------------------------------------ | | | A B C | | | -------------- ------------ ------------ net2 net3 net4 net1 will be connected to the global internet in the near future, via a router (R). The assigned Internet addresses for our department are 131.114.9.*, and this appears to be the main source of problems. Machines A, B and C are Unix boxes (HP9000 and others) with two Ethernet interfaces. net2, net3, net4 are used to support communication between groups of (disk/diskless) X workstations and their servers. Our problem is to configure the network, especially the routing nodes (A,B,C), so that each machine on each subnet can see the other and the external world. Don't know about the router R, but apparently I can only use a byte-aligned netmask on the Unix nodes. Thus each node on 'net1' should be given a 'route' command for each node on the subnetworks, instead of a unique 'route' for each subnetwork. Also, configuration of the nodes on net2..net4 appears to be a problem (lots of 'route add' for them, too). Any ideas other than substituting A, B and C with bridges ? Thanks Luigi ================================================================== Luigi Rizzo Brown University & Univ. di Pisa e-mail: lr@cs.brown.edu, luigi@iet.unipi.it ==================================================================
jason@hpcndjdz.CND.HP.COM (Jason Zions) (05/14/91)
global internet | R | net1 ------------------------------------------ | | | A B C | | | -------------- ------------ ------------ net2 net3 net4 I don't know about your other routers, but HP 9000 Unix boxes do support non-byte aligned netmasks; the HP internal network uses a netmask of 255.255.248.0 on a class A network. Seems to me that you should configure all the nodes on net2 with a default route through A's net2 address; similarly for net3 and B and net4 and C. Each of the routers B C and R should have routes for the net2 network through A's net1 address; similarly for B and net3, C and net4. Also, the A B and C routers should use router R as their default route; this should give everyone in your net visibility to the outside world as well. The tricky (or ugly) part is what to do about the nodes on net1. You could configure them with the specific routes for A/net2, B/net3 and C/net4 while using R as the default router. Or, you could use just R as the default router and depend on ICMP Redirect messages from R to install per-node routes in the routing table on the net1 system. Finally, you could configure the nodes on net1 to use proxy ARP (assuming all of A, B, C, and R support it). Personally, I'd recommend the first configuration; it's a bot of a pain to get all the systems on net1 configured, but the performance and network impact are optimized. Using default routes on the net2/net3/net4 nodes should make them relatively easy to configure. It is absolutely not necessary to add scads of per-node routes by hand; if you use the second alternative for configuring your net1 nodes, per-node routes should be created automatically by the ICMP Redirects. Good luck. -- This is not an official statement of The Hewlett-Packard Company. No warranty is expressed or implied. The information included herein is not to be contrued as a committment on HP's part. The devil made me do it. This won't save me from the lawyers' wrath, but it can't hurt. Jason Zions The Hewlett-Packard Company Colorado Networks Division 3404 E. Harmony Road Mail Stop 102 Ft. Collins, CO 80525 USA jason@cnd.hp.com (303) 229-3800