routing question...

Michael D. Setzer II mikes at kuentos.guam.net
Sun Nov 14 14:05:21 UTC 2004


I've come up with a solution to my problem, but not sure it is the 
best.

The problem I've got is that my college has the entire campus setup 
on one physical network with 3 class C blocks. The classroom 
machines get IP addresses from the dhcp server, but it is totally 
random, some will get addresses from the 71 block, and others from 
the 73 block. For using the internet, that isn't a problem, but for 
machine to machine access, it presents one. The only link between 
the class C networks is a 10MB router, so any communication 
between Class C networks drops to 10MB instead of the 100MB. 
Transfers between machines in same Class C can go as high as 
8MB, whereas different Class C's drops to a max of about 400KB. 
Since everything is on a single physical network, I've added special 
routing entries for Windows, and now want to do the same for Linux. 
I used a simple basic program in Windows, but seem to get the 
same results with this script in Linux

ip=`ifconfig eth0 | grep Mask | cut -c21-35`
route add -net 202.128.71.0/24 gw $ip
route add -net 202.128.73.0/24 gw $ip
route add -net 202.128.72.0/24 gw $ip

It gets the ip address from the ifconfig, and then creates routes for 
all three networks, since I don't know what IP address a machine 
will get. 

The machines boot in 98, XP, or Linux, and I've also used G4U BSD 
for copying. I've seen machines get 4 different IPs booting up with 
one after another, but sometimes 2 of the 4 will be the same. 

About 5 years ago, when I was running the student labs, I had 
separate segments for each classroom, and only had public IPs on 
the 4 servers. Then the ADMIN MIS took over everything, and 
moved it to a single physical network. I've even got a Linux Fedora 
machine setup with 9 Ethernet ports, one connected to the 
backbone, with the other 8 ports setup for separate private IP blocks 
with DHCP behind the IPTABLES firewall. Only problem is that I 
only have 1 machine in my office hooked up to one port. 

Thanks for any suggestions.

+----------------------------------------------------------+
  Michael D. Setzer II -  Computer Science Instructor      
  Guam Community College  Computer Center                  
  mailto:mikes at kuentos.guam.net                            
  http://www.guam.net/home/mikes
  Guam - Where America's Day Begins                        
+----------------------------------------------------------+

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