Why set up a home net

• Shared facilities: hard disk, printer
• Shared access to the internet
• It's the best way to learn what's going on

Ethernet cards

• Card settings (either autosensed or with diskette software):
  • Base address (typically 0x300 or 0x320)
  • Int number (typically 10 or 11)
• Checking settings on a working system (with ifconfig)
  down [11]% /sbin/ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:00:B4:39:DB:18
inet addr:207.161.150.xxx Bcast:207.161.150.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:25612670 errors:0 dropped:3 overruns:0 frame:2627
TX packets:3547293 errors:0 dropped:0 overruns:0 carrier:0
collisions:7394
Interrupt:11 Base address:0x320

Wiring types

• Coax (or 10Base2) looks like cable video line
  • coaxial wire
  • uses linear topology
  • advantages: simpler linear topology, easier to expand, no hub
  • disadvantages: wiring a bit harder to pull, harder to add BNC connectors, trailing edge technology
• 10BaseT or 100BaseT
  • twisted pairs of wires looks like telephone line
  • star topology
  • advantages: easy to get fixed lengths, easy to upgrade to 100BaseT, easier to pull
  • disadvantages: hubs need power, more complicated to expand

Setting up a home network

• special addresses
  • 10.xxx.xxx.xxx (netmask: 255.0.0.0)
  • 172.16.xxx.xxx (netmask: 255.255.0.0)
  • 192.168.xxx.xxx (netmask: 255.255.255.0)
• assigning addresses to machines
  • control-panel or
  • mdoob@up ~]$ cat /etc/hosts
127.0.0.1 localhost localhost.localdomain
10.0.0.3 down
10.0.0.6 charm
10.0.0.1 up
• Setting the netmask
  • control-panel or
  • [mdoob@up network-scripts]$ cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
USERCTL=no
ONBOOT=yes
BOOTPROTO=
BROADCAST=10.255.255.255
NETWORK=10.0.0.0
NETMASK=255.0.0.0
IPADDR=10.0.0.1
• getting Linux to recognize your ethernet card
  • control-panel or
  • [mdoob@up ~]$ cat /etc/conf.modules
alias eth0 ne
options ne io=0x300 irq=10
• checking things out with ifconfig (same as in the section on Ethernet cards)

An example: the Quark home LAN

The quark network using coax cables (linear topology)

The quark network using 10BaseT cables (star topology)

Connecting to the outside world using IP masquerading

• Getting the software from: X/OS
• The machine that acts as a router (the masquerading machine, down=10.0.0.3 in the example above)
  • setting up two ethernet cards, or
  • setting up one card and one modem
  • control-panel
  • down [6]% cat /etc/conf.modules
alias eth0 ne
alias eth1 ne
options ne io=0x320,0x300 irq=11,10
  • gateway setting and IP forwarding
    down [11]% cat /etc/sysconfig/network
NETWORKING=yes
FORWARD_IPV4=yes
HOSTNAME=down
GATEWAYDEV=eth0
GATEWAY=207.161.150.1
  • Commands for IP masquerading:
    • RedHat 5.2 ipfwadm
      /sbin/depmod -a
/sbin/modprobe ip_masq_ftp.o
/sbin/modprobe ip_masq_raudio.o
/sbin/modprobe ip_masq_irc.o
/sbin/ipfwadm -F -p deny
/sbin/ipfwadm -F -a accept -m -S 10.0.0.0/24 -D 0.0.0/0

    • RedHat 6.0 ipfwadm-wrapper replaces ipfwadm
  • Checking settings (with ifconfig) down [12]% /sbin/ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0
UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1
RX packets:24544 errors:0 dropped:0 overruns:0 frame:0
TX packets:24544 errors:0 dropped:0 overruns:0 carrier:0
collisions:0

eth0 Link encap:Ethernet HWaddr 00:00:B4:39:DB:18
inet addr:207.161.150.xxx Bcast:207.161.150.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:25615830 errors:0 dropped:3 overruns:0 frame:2627
TX packets:3549328 errors:0 dropped:0 overruns:0 carrier:0
collisions:7395
Interrupt:11 Base address:0x320

eth1 Link encap:Ethernet HWaddr 00:00:B4:39:DC:89
inet addr:10.0.0.3 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:161938 errors:0 dropped:0 overruns:0 frame:0
TX packets:195339 errors:0 dropped:0 overruns:0 carrier:0
collisions:57
Interrupt:10 Base address:0x300
• Other machines on the home network (the masqueraded machines)
  • gateway settings
    [mdoob@up sysconfig]$ cat /etc/sysconfig/network
NETWORKING=yes
FORWARD_IPV4=no
HOSTNAME=up
GATEWAYDEV=eth0
GATEWAY=10.0.0.3
• Checking things out with netstat -M

Using X Window applications with IP masquerading

• the problem
• using vnc as a solution
• getting vnc over the net from: AT&T Laboratories Cambridge.