Our entire address space is 202.144.139.0/24
202.144.139.0 = 11001010 10010000 10001011 00000000 Prefix /24 ++++++++++++++++++++++++++ Host part xxxxxxxx Total number of IPs = 2^8 = 256 (00000000 to 11111111) Lowest IP: 11001010 10010000 10001011 00000000 = 202.144.139.0 Highest IP: 11001010 10010000 10001011 11111111 = 202.144.139.255 For this exercise, we will divide this up as follows: +-------+-------+-------+-------+-------+-------+---------------+ |.0/29 |.8/29 |.16/29 |.24/29 |.32/29 | | | | 0-7 | 8-15 | 16-23 | 24-31 | 32-39 | | | +-------+-------+-------+-------+-------+-------+---------------+ separate subnet for each group ... +---------------------------------------------------------------+ |.192/26 | | 192 - 255 | +---------------------------------------------------------------+ backbone TABLE ONE 202.144.139.192/26 Classroom backbone ------------------ ------------------ 202.144.139.193 Group one (PC1-3) border router 202.144.139.194 Group two (PC4-6) border router 202.144.139.195 Group three (PC7-9) border router 202.144.139.196 Group four (PC10-12) border router 202.144.139.197 Group five (PC13-15) border router Q. What is the netmask for a /26 network? ______________________ There are separate /29 networks for the *private* networks between machines on each desktop TABLE TWO 202.144.139.0/29 Group one 202.144.139.8/29 Group two 202.144.139.16/29 Group three 202.144.139.24/29 Group four 202.144.139.32/29 Group five Q. What is the netmask for a /29 network? ______________________
Each group has one machine which will be the ROUTER, two machines which are CLIENTS, and a private ethernet network (hub) between them.
CLIENT CLIENT ROUTER +-------+ +-------+ +-------+ 202.144.139.___ | PC __ | | PC __ | | PC __ |----------> to backbone +-------+ +-------+ +-------+ xl1 | xl0 | xl0 | xl0 | 202.144.139.___ | 202.144.139.___ | 202.144.139.___ | | | | +-----+ | +------------------ | hub | ------------------+ +-----+
Don't change /etc/rc.conf, because we don't want these changes to be permanent. The commands you will need are:
ifconfig # show interfaces ifconfig xl0 x.x.x.x/p # configure interface ifconfig xl0 x.x.x.x netmask y.y.y.y # (alternative form) netstat -nr # show routes (ignore ipv6) route add x.x.x.x/p z.z.z.z # add a route to network x.x.x.x/p # via next-hop z.z.z.z route add -net x.x.x.x -netmask y.y.y.y z.z.z.z # (alternative form) route delete x.x.x.x/p # delete a route route delete default # delete defaultroute ping x.x.x.x # send test packets (Ctrl-C to stop) traceroute -n x.x.x.x # show route to destination
Remember that the next hop gateway (z.z.z.z) must be an address on one of the networks which you are DIRECTLY connected to.
Can you ping other routers on the backbone? Can you ping other clients in other groups? Debug the problems.