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Configuring TCP/IP
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Objectives
After completing this unit, students should be able to:Configure TCP/IPTest the TCP/IP configuration
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Configure Hostname
Done with the hostname command# hostname tux
To configure hostname permanently, configure the
startup file appropriate for your distributionRed Hat: /etc/sysconfig/networkSuSE: /etc/HOSTNAME
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Configure Adapters
Most adapters will be autodetected while booting thesystem - no further configuration necessary
Some complications
Multiple adaptersSome adapters are not probed correctly
To configure adapters manually, change
lilo.conf or grub.conf (if support compiled into kernel)/etc/modules.conf (if support compiled as modules)# cat /etc/lilo.conf.image=/boot/bzImage
append="eth0=0x300,2,3c509".# cat /boot/grub/grub.conf.title Red Hat Linux (2.4.18-3)
kernel /vmlinuz-2.4.18-3 ro root=/dev/hda7 eth0=0x300,2,3c509.# cat /etc/modules.confalias eth0 3c509options eth0 io=0x300 irq=2
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Assign IP Addresses
Done with ifconfig# ifconfig eth0 129.33.151.7 netmask 255.255.255.0 up
ifconfig without options shows the current configuration
Make permanent by adding to the configuration filesRed Hat: /etc/sysconfig/networking/devices/ifcfg-SuSE: /etc/sysconfig/network/ifcfg-
To activate/deactivate an interface manually, using theifcfg- information, use ifup and ifdown# ifup eth0# ifdown eth0
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Configuring Wireless Adapters
Wireless (IEEE 802.11) adapters are configured likeethernet adapters with a few extra parameters:Link speed (use "auto")SSID (Service Set IDentifier)WEP encryption keys and settings
Done with iwconfig command:# iwconfig eth1 rate auto essid "IBMEDUC" enc "1234567890"
Configuration generally stored alongside IP configurationin ifcfg- files
Can use redhat-config-network or yast to configurewireless parameters
Other useful commands:iwlist : List information from wireless networkiwspy : Display signal quality and strength
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Configuring the Default Route
The Default Route is the "way out" of your local networkShould be added to the routing table:# route add default 129.33.151.1
route without options gives all current routesMake permanent by adding to the configuration files
Red Hat: /etc/sysconfig/network or /etc/sysconfig/networking/devices/ifcfg- (*)SuSE: /etc/sysconfig/network/routes or /etc/sysconfig/network/ifcfg- (*)
(*) Configuring a per-device default route is only useful one.g. laptops, where not all devices are used simultaneously
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/etc/hosts
# The format of the file is:# # comments
127.0.0.1 loopback localhost
129.33.151.7 sys7129.33.151.1 sys1 router129.33.151.201 sys201 dns1129.33.151.202 sys202 dns2
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Testing Your Configuration
Verify local interfacesVerify routing
Verify ARP table
Verify connectivity
Verify hostname resolution
Verify open ports
V if L l I f
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Verify Local Interfaces
# ifconfigeth0 Link encap:Ethernet HWaddr: 00:50:56:81:00:01
inet addr:129.33.151.7 Bcast:129.33.151.255 Mask:255.255.255.0UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:49 errors:0 dropped:0 overruns:0 frame:0TX packets:0 errors:0 dropped:0 overruns:0 carrier:0collisions:0 txqueuelen:100interrupt:9 Base address:0x1000
lo Link encap:Local Loopbackinet addr:127.0.0.1 Mask:255.0.0.0UP LOOPBACK RUNNING MTU:3924 Metric:1RX packets:22 errors:0 dropped:0 overruns:0 frame:0
TX packets:22 errors:0 dropped:0 overruns:0 carrier:0collisions:0 txqueuelen:0
V if R i
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Verify Routing
# routeKernel IP routing tableDestination Gateway Genmask Flags Metric Ref Use Iface129.33.151.0 * 255.255.255.0 U 0 0 0 eth0
default 129.33.151.1 0.0.0.0 UG 0 0 0 eth0
V if ARP T bl
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Verify ARP Table
# arp Address HWtype HWaddress Flags Mask Iface
129.33.151.1 ether 00:A0:24:8A:85:BA C eth0
V if C ti it
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Verify Connectivity
# ping 129.33.151.1PING 129.33.151.1 (129.33.151.1) from 129.33.151.7 : 56(84) bytes of data.64 bytes from 129.151.33.1: icmp_seq=0 ttl=255 time=5.0 ms64 bytes from 129.151.33.1: icmp_seq=1 ttl=255 time=0.7 ms64 bytes from 129.151.33.1: icmp_seq=2 ttl=255 time=0.7 ms64 bytes from 129.151.33.1: icmp_seq=3 ttl=255 time=0.7 ms^C--- 129.151.33.1 ping statistics ---4 packets transmitted, 4 packets received, 0% packet lossround-trip min/avg/max = 0.7/1.7/5.0 ms
Verify Hostname Resolution
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Verify Hostname Resolution
# host sys7sys7.my_domain.com has address 129.33.151.7# host 129.33.151.77.151.33.129.IN-ADDR.ARPA domain name pointer sys7.my_domain.com
Verify Open Ports
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Verify Open Ports
# netstat -a
Active Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address Statetcp 0 0 *:www *:* LISTENtcp 0 0 *:smtp *:* LISTENtcp 0 0 *:printer *:* LISTEN
tcp 0 0 *:auth *:* LISTENtcp 0 0 *:finger *:* LISTENtcp 0 0 *:exec *:* LISTENtcp 0 0 *:login *:* LISTENtcp 0 0 *:shell *:* LISTEN
tcp 0 0 *:telnet *:* LISTENtcp 0 0 *:ftp *:* LISTENudp 0 0 *:ntalk *:*udp 0 0 *:talk *:*raw 0 0 *:icmp *:* 7
raw 0 0 *:tcp *:* 7
Checkpoint
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Checkpoint
1. What is a good first command to use to test whether twohosts can talk to each other on a network?
2. What command can you use to test for proper nameresolution, both name to address and address to name?
3. What command will display what is in your arp cache?
4. What command will show the network status includinginput and output packets transmitted on a networkinterface?
Unit Summary
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Unit Summary
To configure TCP/IP the following steps should be takenConfigure adaptersSet a hostnameConfigure IP addressesDefine basic routingConfigure name resolution
Usually these steps are part of the installation process
To test your configuration, various commands are useful:ifconfigroutenetstatarpping