1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Linux Professional Institute Certification — 102 Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Angus Lees gus@inodes.org Geoffrey Robertson ge@ffrey.com Nick Urbanik nicku@nicku.org This document Licensed under GPL—see section 16 hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf 2005 July Debugging DNS DHCP License Of This Document Outline 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topic 112 Networking Fundamentals [14] Where we are up to 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route 1.112.1 Fundamentals of TCP/IP [4] 1.112.3 TCP/IP configuration and troubleshooting [7] 1.112.4 Configure Linux as a PPP client [3] netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Description of Objective 1.112.3 TCP/IP configuration and troubleshooting 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Candidates should be able to view, change and verify configuration settings and operational status for various network interfaces. This objective includes manual and automatic configuration of interfaces and routing tables. This especially means to add, start, stop, restart, delete or reconfigure network interfaces. It also means to change, view or configure the routing table and to correct an improperly set default route manually. Candidates should be able to configure Linux as a DHCP client and a TCP/IP host and to debug problems associated with the network configuration. Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Key files, terms, and utilities include: I 1.112.3 TCP/IP configuration and troubleshooting 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees /etc/HOSTNAME or /etc/hostname — a text file holding the hostname /etc/hosts — a file mapping IP addresses ↔ hostnames /etc/networks — an obsolete file that maps only classful network addresses ↔ names /etc/host.conf — an obsolete file replaced by nsswitch /etc/resolv.conf — configuration file used when system looks up a name or address /etc/nsswitch.conf — name service switch configuration file: determines how system looks up name and various other things ifconfig — a command to show and configure network interfaces route — a command to show and configure network routes dhcpcd, dhcpclient, pump — DHCP clients Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Key files, terms, and utilities include: II 1.112.3 TCP/IP configuration and troubleshooting 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees host — a program to query and debug DNS servers hostname (domainname, dnsdomainname) — commands to show the hostname, and NIS domain settings netstat — a command that shows what service is listening on what port ping — sends ICMP ECHO_REQUEST to hosts, displays time it takes to get an answer traceroute — command to show the path that a network connection takes, showing routes along the way tcpdump — packet sniffer command that displays the contents of packets received on a network interface the network scripts run during system initialization. Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document TCP/IP Configuration and Troubleshooting Resources of Interest 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route Linux Networking HOWTO by Joshua Drake : http://tldp. org/HOWTO/Net-HOWTO/index.html Linux Ethernet-Howto by Paul Gortmaker : http: //tldp.org/HOWTO/Ethernet-HOWTO.html netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document ifconfig – Low level network config 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Network interface configuration $ sudo ifconfig eth0 192.168.7.26 netmask 255.255.255.0 broadcast 192.168.7.255 ← $ sudo ifconfig eth0 down ← route – Low level network config 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces $ sudo route add -net 192.168.7.0 netmask 255.255.255.0 dev eth0 ← $ sudo route add default gw 192.168.7.1 ← View routing table: $ route -n ← Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Ports in use Routing table Interfaces Multicast groups Masqueraded connections Statistics netstat -a -u -t netstat -r netstat -i netstat -g netstat -M netstat -s Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Network debugging 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context ping Try to bounce an ICMP packet off a host Good for reachability, round trip delay, packet loss traceroute Show the network path to a particular host Good for testing routing problems, “which ISP screwed up” tcpdump Dump raw network traffic Exceptional for diagnosing network problems involving a particular host Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Outline 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document tcpdump again tcpdump is your friend, learn to use it 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources $ sudo tcpdump -i ppp0 not port ssh tcpdump: listening on ppp0 Configuring network 21:54:32.913475 10.0.128.107.1024 > 10.0.128.97.domain: 20147+ A? interfaces fatso.urnet.com.au. (36) (DF) Adding routes with 21:54:33.102745 10.0.128.97.domain > 10.0.128.107.1024: 20147* 1/3/3 route (178) (DF) netstat 21:54:33.103766 10.0.128.107 > 203.26.250.2: icmp: echo request (DF) Troubleshooting Tools 21:54:33.352745 203.26.250.2 > 10.0.128.107: icmp: echo reply Using tcpdump 21:54:34.102912 10.0.128.107 > 203.26.250.2: icmp: echo request (DF) 21:54:34.302745 203.26.250.2 > 10.0.128.107: icmp: echo reply hostname 21:56:09.908636 10.0.128.107.1068 > 203.26.250.2.www: nsswitch.conf S 1245080954:1245080954(0) win 5840 (DF) [tos 0x10] 21:56:10.052743 203.26.250.2.www > 10.0.128.107.1068: /etc/hosts S 3633684004:3633684004(0) ack 1245080955 win 5792 (DF) 21:56:10.052869 10.0.128.107.1068 > 203.26.250.2.www: . ack 1 win 5840 /etc/resolv.conf (DF) [tos 0x10] Debugging DNS 21:56:12.977510 10.0.128.107.1068 > 203.26.250.2.www: P 1:2(1) ack 1 DHCP win 5840 (DF) [tos 0x10] License Of This Document /etc/HOSTNAME or /etc/hostname 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources System scripts set the hostname from one of these files during boot, using the hostname command. dnsdomainname, ypdomainname, nisdomainname and domainname are variations on hostname Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf domainname gives the NIS domainname, NOT the DNS domain /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document /etc/nsswitch.conf “Name Service Switch” configuration passwd: group: shadow: hosts: networks: protocols: services: ethers: rpc: netgroup: compat compat compat files dns files db db db db nis files files files files 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document /etc/networks 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Labels for network addresses Only supports class A, B or C addresses (not CIDR) Rarely used or kept up to date localnet 192.168.1.0 /etc/hosts Hostname to IP address mapping, mostly superseded by DNS Still matters before DNS is running 127.0.0.1 localhost 192.168.1.1 cat.pasture.com.au cat 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname # The following lines are desirable for IPv6 capable hosts nsswitch.conf ::1 fe00::0 ff00::0 ff02::1 ff02::2 ff02::3 ip6-localhost ip6-loopback ip6-localnet ip6-mcastprefix ip6-allnodes ip6-allrouters ip6-allhosts /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document /etc/host.conf — Resolver configuration 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Various keywords to tweak non-DNS-specific resolver behaviour Rarely modified; most options no longer relevant See $ man host.conf ← order hosts,bind multi on hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document /etc/resolv.conf — DNS configuration 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces DNS configuration for resolver Nameserver defaults to 127.0.0.1, search suffix defaults to DNS domain name search pasture.com.au nameserver 10.0.128.97 Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Outline 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document DHCP License Of This Document Debugging DNS with host 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces host performs various DNS queries host [options] hostname [server] Common options: -v verbose -l list all hosts in a domain (using AXFR) -t query type (“-t any” is useful) Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document DHCP 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources “Dynamic Host Control Protocol” configures networking details, DNS, etc automatically by querying a “DHCP server” Various DHCP clients: dhcpclient Comes with ISC DHCP server, highly configurable dhcpcd pump Simple DHCP client written by RedHat udhcpc Very small DHCP client Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document Topics Covered Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools Using tcpdump hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS host DHCP License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document License Of This Document 1.112.3 TCP/IP configuration and troubleshooting Weight 7 Angus Lees Context Objective Resources Copyright c 2005, 2003 Angus Lees gus@inodes.org, Geoffrey Robertson and Nick Urbanik . Permission is granted to make and distribute verbatim copies or modified versions of this document provided that this copyright notice and this permission notice are preserved on all copies under the terms of the GNU General Public License as published by the Free Software Foundation—either version 2 of the License or (at your option) any later version. Configuring network interfaces Adding routes with route netstat Troubleshooting Tools hostname nsswitch.conf /etc/networks /etc/hosts /etc/host.conf /etc/resolv.conf Debugging DNS DHCP License Of This Document