Linux Lab 04 Troubleshoot Network

Linux Workshop

Lab 4 Troubleshoot the network Requirements

Quick Reference Objectives to learn

➢ Running Linux connected to a network. ➢ nmap and mtr package installed. ➢ Network configuration file without MAC address

Troubleshoot network environment

or with a correct MAC address (HWADDR): /etc/sysconfig/network/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0 ➢ Classroom or Internet NTP server.

To Do 1. Which information is not displayed by the ifconfig command?

ping host

#Check using ICMP. Stop with

ifconfig

#or /sbin/ifconfig

cat /etc/resolv.conf

#Show DNS server in use

route

#Show routes & default gateway

netstat

-r

#Show routes & default gateway

netstat

-antp

#Show listening tcp ports

netstat

-anup

#Show listening udp ports

nmap

host

#Show exposed ports on host

host

ns.nl

#Check name resol. via DNS-srv in use

host -a

ns.nl

#Check all

dig

nu.nl

#Check name resol. via DNS-srv in use

dig

@4.2.2.1 nu.nl

#Check name resol. via other (@)DNS-srv

mtr

www.whitehouse.com #Show continuous traceroute

traceroute www.whitehouse.com #Check route using ICMP

IP address

ntptrace

subnet mask

ntpdate

MAC address

/etc/init.d/xntpd stop or

#Check timesync (Wait 5 minutes aft sync) ntp.xs4all.nl

#Sync time once. First stop ntp daemon: /etc/init.d/ntpd stop

default gateway name server 2. The classroom may not have a gateway and name server. Some of the commands will not show spectacular results, but they are the basic network troubleshooting commands. Try the Quick Reference commands from ping to traceroute. 3. Synchronize the time with the classroom or Internet NTP server and check the synchronization status.

Theory Modules LPIC 1 Certification Bible, isbn 0-7645-4772-0 ➢ p. 561 Ch. 15 Networking Fundamentals

Extra References ➢ www.tldp.org ➢ www.snort.org ➢ http://netsaint.sourceforge.net/download/

© October 2, 2005, wiki.novell.com/index.php/Roberts_Quick_References, author of Foundations of Linux networking