Tcpip Linux

8/6/2019 Tcpip Linux

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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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f


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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

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