Networking for GNU/Linux Ahmed D. Mekkawy AKA linuxawy [email_address]

Part I : TCP/IP overview Though you should already know TCP/IP, this quick overview Is made to make sure that all course attendees are aligned.

Though you should already know TCP/IP, this quick overview Is made to make sure that all course attendees are aligned.

OSI Model Vs. TCP/IP Model

TCP/IP Connection Types TCP: Connection Oriented Initiating a connection: 3 Way Handshaking Finalizing a connection. UDP: Connectionless ICMP: Error, Control, Information.

TCP: Connection Oriented

Initiating a connection: 3 Way Handshaking

Finalizing a connection.

UDP: Connectionless

ICMP: Error, Control, Information.

Ports Lower numbered Vs. Higher numbered ports. Ports can handle multi-connection. Listening Ports.

Lower numbered Vs. Higher numbered ports.

Ports can handle multi-connection.

Listening Ports.

TTL Time To Live. Decreased by 1 with each router passed. Designed to forbid packets to flow endlessly because of a mis-configured router or so.

Time To Live.

Decreased by 1 with each router passed.

Designed to forbid packets to flow endlessly because of a mis-configured router or so.

IP IPv4 Vs. IPv6 Private IPs (eg. 192.168.xxx.xxx , 10.xxx.xxx.xxx) Localhost (127.xxx.xxx.xxx) Subnets & netmask. Network & Broadcast IP.

IPv4 Vs. IPv6

Private IPs (eg. 192.168.xxx.xxx , 10.xxx.xxx.xxx)

Localhost (127.xxx.xxx.xxx)

Subnets & netmask.

Network & Broadcast IP.

Gateways Routing. Natting. Port-Forwarding. Firewalling.

Routing.

Natting.

Port-Forwarding.

Firewalling.

Hub Vs. Switch Switch Vs. Hub Switch Vs. Router Access Points, are they Switches or Hubs?

Switch Vs. Hub

Switch Vs. Router

Access Points, are they Switches or Hubs?

Main Network Services DNS DHCP

DNS

DHCP

Part II: Configure wired NIC

The Native way ifconfig eth0 10.0.0.1 netmask 255.255.255.0 up Ifup & ifdown Multiple Ips on the same NIC: Child interfaces: Ifconfig eth0:0 10.0.0.2 netmask 255.255.255.0 up Routing: route add default gw 192.168.0.1 eth0 route add -net 10.0.0.1 netmask 255.0.0.0 gw 192.168.0.200 eth0 DHCP client: dhclient eth0

ifconfig eth0 10.0.0.1 netmask 255.255.255.0 up

Ifup & ifdown

Multiple Ips on the same NIC: Child interfaces:

Ifconfig eth0:0 10.0.0.2 netmask 255.255.255.0 up

Routing:

route add default gw 192.168.0.1 eth0

route add -net 10.0.0.1 netmask 255.0.0.0 gw 192.168.0.200 eth0

DHCP client: dhclient eth0

The native way - Contd. hostname /etc/resolv.conf /etc/hosts

hostname

/etc/resolv.conf

/etc/hosts

The Redhat/Fedora way /etc/sysconfig/network-scripts/ifcfg-eth0 Or # File: ifcfg-eth0 DEVICE=eth0 IPADDR=192.168.1.100 NETMASK=255.255.255.0 BOOTPROTO=static ONBOOT=yes # The following settings are optional BROADCAST=192.168.1.255 NETWORK=192.168.1.0 # File: ifcfg-eth0 DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes

/etc/sysconfig/network-scripts/ifcfg-eth0

Or

Redhat way - Contd. /etc/sysconfig/network Static routes can be added per NIC: NETWORKING=yes HOSTNAME=bigboy GATEWAY=192.168.1.1 # File /etc/sysconfig/network-scripts/route-wlan0 # 10.0.0.0/8 via 192.168.1.254

/etc/sysconfig/network

Static routes can be added per NIC:

Debian / Ubuntu way /etc/network/interfaces # File: /etc/network/interfaces # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth1 iface eth1 inet static address 216.10.119.240 netmask 255.255.255.224 network 216.10.119.224 broadcast 216.10.119.255 gateway 216.10.119.241 # dns-* options are implemented by the resolvconf dns-nameservers 216.10.119.241 up route add -net 10.0.0.0 netmask 255.0.0.0 gw 216.10.119.225 eth1

/etc/network/interfaces

Debian / Ubuntu way - Contd. /etc/network/interfaces Contd /etc/hostname auto eth1:1 iface eth1:1 inet static address 216.10.119.239 netmask 255.255.255.224 # The secondary network interface auto eth0 iface eth0 inet dhcp

/etc/network/interfaces Contd

/etc/hostname

Part III: Configuring wireless

Wireless Network ls /sys/classes/net ls /sys/classes/net/eth1 (look for “wireless”) iwlist eth1 scan Ifconfig eth1 0.0.0.0 up iwconfig eth1 mode Managed iwconfig eth1 channel 6 Iwconfig eth1 key restricted s:MyKey # for WEP

ls /sys/classes/net

ls /sys/classes/net/eth1 (look for “wireless”)

iwlist eth1 scan

Ifconfig eth1 0.0.0.0 up

iwconfig eth1 mode Managed

iwconfig eth1 channel 6

Iwconfig eth1 key restricted s:MyKey # for WEP

Wireless Network - Contd. If the encryption is WAP: Ifconfig eth1 0.0.0.0 up Killall wpa_supplicant wpa_passphrase linksys mysecret > /etc/wpa_supplicant.conf Iwconfig eth1 mode Managed Iwconfig eth1 essid linksys Iwconfig eth1 channel 11 wpa_supplicant -i eth1 -c /etc/wpa_supplicant.conf -d -D wext &

If the encryption is WAP:

Ifconfig eth1 0.0.0.0 up

Killall wpa_supplicant

wpa_passphrase linksys mysecret > /etc/wpa_supplicant.conf

Iwconfig eth1 mode Managed

Iwconfig eth1 essid linksys

Iwconfig eth1 channel 11

wpa_supplicant -i eth1 -c /etc/wpa_supplicant.conf -d -D wext &

Wireless Network - Contd. Then get the IP normally through dhcp or through ifconfig command. dhclient eth1

Then get the IP normally through dhcp or through ifconfig command.

dhclient eth1

Reference http://www.linuxhomenetworking.com linuxac.org Magazine Jan, 2008

http://www.linuxhomenetworking.com

linuxac.org Magazine Jan, 2008