1 COP 4343 Unix System Administration Unit 11: Networking – basic concepts: IP, TCP, UDP, DHCP – devices: setup, status

2 Networking Technologies Ethernet –100Mbs, 1Gbs DSL, cable –up to 6Mbs T1 (DS1) –1.5Mbs DS3 –45Mbs OCx –50Mbs to 40Gbs WiFi: (a) 6 to 54Mbs (b) 1 to 11Mbs (g) up to 54Mbs (n) more WiMax: –386Kbs to 10Mbs Modem –56Kbs

3 Network Devices ethernet card –eth0 point-to-point protocol –ppp0 used to connect a modem to an ISP loop back –lo uniquely identified via MAC address

4 Basic concepts: IP numbers to know: –IP 32bit unique identifier, written as quad –network first n bits of IP number, written as “/n” 8 - class A, 16 - class B, 24 - class C more than 24 - class D –netmask 32 bit number with first n bits all 1, rest 0 –broadcast network number (first n bits), rest all 1 –gateway IP –name server IP to 14 /

5 ip protocols icmp: Internet control message protocol –control protocol ping, traceroute tcp: transmission control protocol –connection oriented, guaranteed delivery –basis for: http, ftp, smtp, ssh udp: user datagram protocol –best effort –basis for: dns, rtp

6 dhcp dynamic host configuration protocol –client obtains network setup from server –assignment has duration: lease client –dhclient server –dhcpd

7 Network Configuration ifconfig –parameters: network interface, IP address, mask, mtu, etc. –without parameters: status of all configured network interfaces route to gateway –route add default gw eth0 name servers or /etc/hosts –/etc/resolv.conf

8 Network Configuration Scripts /etc/sysconfig/network NETWORKING=yes HOSTNAME=instructor.ege.com /etc/sysconfig/network-scripts –ifcfg-eth0 DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes

9 ifcfg-eth0 example DEVICE=eth0 BROADCAST= IPADDR= NETMASK= NETWORK= ONBOOT=no

10 Manual management ifup ifdown for specific device –ifdown eth0 –ifup eth0

11 Network Troubleshooting route –display kernel routing table ping –send control packet to host traceroute –check intermediate nodes on path to host arp –check MAC address vs. IP number