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![Network Diagnostic ToolsNetwork Diagnostic Tools
●
host DOMAIN_NAME [DNS_SERVER]host DOMAIN_NAME [DNS_SERVER]
– Lookup A record of a domain nameLookup A record of a domain name
– Common optionsCommon options
t t : query type: query type
v v : verbose output: verbose output
W W nn : time out in: time out in nn secondsseconds
●
host IP [DNS_SERVER]host IP [DNS_SERVER]
– The reverse DNS lookupThe reverse DNS lookup](https://image.slidesharecdn.com/chap18net-150606075134-lva1-app6891/75/Chap-18-net-22-2048.jpg)
![Network Diagnostic ToolsNetwork Diagnostic Tools
●
dig DOMAIN_NAME [@DNS_SERVER]dig DOMAIN_NAME [@DNS_SERVER]
– Lookup domain name informationLookup domain name information
– Common optionsCommon options
x IP x IP : reverse lookup: reverse lookup
+short +short : short answer: short answer
+trace +trace : trace recursive lookup from root down: trace recursive lookup from root down](https://image.slidesharecdn.com/chap18net-150606075134-lva1-app6891/75/Chap-18-net-23-2048.jpg)
Uploaded byKenny (netman)
Chap 18 net
This document discusses network configuration and diagnostic tools in Linux. It describes how to view interface configuration and address information using ifconfig and ip addr show. It also covers changing IP and route settings persistently in configuration files and using ifup/ifdown. Tools like ping and traceroute are presented for network diagnostics.
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Chap 18 net
- 1. Chapter 18Chapter 18 NetworkConfigurationNetwork Configuration
- 2. Network Devices inLinuxNetwork Devices in Linux ● lolo – Loop back deviceLoop back device – IP address is 127.0.0.1 permanentlyIP address is 127.0.0.1 permanently ● ethethNN – Ethernet interfaceEthernet interface – Device number starting from 0Device number starting from 0 ● wlanwlanNN – Wireless interfaceWireless interface – Device number starting from 0Device number starting from 0
- 3. Display Interface ConfigurationDisplayInterface Configuration ● ifconfigifconfig eth0 Link encap:Ethernet HWaddr 00:16:d3:32:ea:dceth0 Link encap:Ethernet HWaddr 00:16:d3:32:ea:dc inet addr:192.168.100.57 Bcast:192.168.100.255 Mask:255.255.255.0inet addr:192.168.100.57 Bcast:192.168.100.255 Mask:255.255.255.0 inet6 addr: fe80::216:d3ff:fe32:eadc/64 Scope:Linkinet6 addr: fe80::216:d3ff:fe32:eadc/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:18973 errors:0 dropped:0 overruns:0 frame:0RX packets:18973 errors:0 dropped:0 overruns:0 frame:0 TX packets:16624 errors:0 dropped:0 overruns:0 carrier:0TX packets:16624 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000collisions:0 txqueuelen:1000 RX bytes:12613255 (12.6 MB) TX bytes:2686873 (2.6 MB)RX bytes:12613255 (12.6 MB) TX bytes:2686873 (2.6 MB) Interrupt:16 Memory:ee000000-ee020000Interrupt:16 Memory:ee000000-ee020000 lo Link encap:Local Loopbacklo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Hostinet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:523 errors:0 dropped:0 overruns:0 frame:0RX packets:523 errors:0 dropped:0 overruns:0 frame:0 TX packets:523 errors:0 dropped:0 overruns:0 carrier:0TX packets:523 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0collisions:0 txqueuelen:0 RX bytes:38418 (38.4 KB) TX bytes:38418 (38.4 KB)RX bytes:38418 (38.4 KB) TX bytes:38418 (38.4 KB)
- 4. Display Address InformationDisplayAddress Information ● ip addr showip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWNUNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host loinet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forevervalid_lft forever preferred_lft forever inet6 ::1/128 scope hostinet6 ::1/128 scope host valid_lft forever preferred_lft forevervalid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000state UP qlen 1000 link/ether 00:16:d3:32:ea:dc brd ff:ff:ff:ff:ff:fflink/ether 00:16:d3:32:ea:dc brd ff:ff:ff:ff:ff:ff inet 192.168.100.57/24 brd 192.168.100.255 scope global eth0inet 192.168.100.57/24 brd 192.168.100.255 scope global eth0 valid_lft forever preferred_lft forevervalid_lft forever preferred_lft forever inet6 fe80::216:d3ff:fe32:eadc/64 scope linkinet6 fe80::216:d3ff:fe32:eadc/64 scope link valid_lft forever preferred_lft forevervalid_lft forever preferred_lft forever
- 5. Display Link InformationDisplayLink Information ● ip link showip link show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWNUNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000state UP qlen 1000 link/ether 00:16:d3:32:ea:dc brd ff:ff:ff:ff:ff:fflink/ether 00:16:d3:32:ea:dc brd ff:ff:ff:ff:ff:ff
- 6. Display Link CharacteristicsDisplayLink Characteristics ● ip s link showip s link show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWNUNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 RX: bytes packets errors dropped overrun mcastRX: bytes packets errors dropped overrun mcast 38418 523 0 0 0 038418 523 0 0 0 0 TX: bytes packets errors dropped carrier collsnsTX: bytes packets errors dropped carrier collsns 38418 523 0 0 0 038418 523 0 0 0 0 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000state UP qlen 1000 link/ether 00:16:d3:32:ea:dc brd ff:ff:ff:ff:ff:fflink/ether 00:16:d3:32:ea:dc brd ff:ff:ff:ff:ff:ff RX: bytes packets errors dropped overrun mcastRX: bytes packets errors dropped overrun mcast 12629558 19078 0 0 0 24512629558 19078 0 0 0 245 TX: bytes packets errors dropped carrier collsnsTX: bytes packets errors dropped carrier collsns 2711702 16782 0 0 0 02711702 16782 0 0 0 0
- 7. Display Routing InformationDisplayRouting Information ● route nroute n Kernel IP routing tableKernel IP routing table Destination Gateway Genmask Flags Metric Ref Use IfaceDestination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.100.11 0.0.0.0 UG 0 0 0 eth00.0.0.0 192.168.100.11 0.0.0.0 UG 0 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0 192.168.100.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0192.168.100.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0
- 8. Display Routing InformationDisplayRouting Information ● ip route showip route show default via 192.168.100.11 dev eth0 proto staticdefault via 192.168.100.11 dev eth0 proto static 169.254.0.0/16 dev eth0 scope link metric 1000169.254.0.0/16 dev eth0 scope link metric 1000 192.168.100.0/24 dev eth0 proto kernel scope link src 192.168.100.57192.168.100.0/24 dev eth0 proto kernel scope link src 192.168.100.57 metric 1metric 1
- 9. Display DNS SettingsDisplayDNS Settings ● cat /etc/resolv.confcat /etc/resolv.conf cat /etc/resolv.confcat /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTENOVERWRITTEN nameserver 192.168.100.11nameserver 192.168.100.11
- 10. Change IP SettingsChangeIP Settings ● Add IP:Add IP: – ifconfig eth0:0 IP/MASKifconfig eth0:0 IP/MASK – ip address add IP/MASK dev eth0ip address add IP/MASK dev eth0 ● Delete IP:Delete IP: – ifconfig eth0:0 downifconfig eth0:0 down – ip address del IP/MASK dev eth0ip address del IP/MASK dev eth0
- 11. Change Route SettingsChangeRoute Settings ● Add route:Add route: – route add net NET/MASK gw GW_IProute add net NET/MASK gw GW_IP – ip route add NET/MASK via GW_IPip route add NET/MASK via GW_IP ● Delete route:Delete route: – route del net NET/MASK gw GW_IProute del net NET/MASK gw GW_IP – ip route del NET/MASK via GW_IPip route del NET/MASK via GW_IP
- 12. Persistent IP SettingsPersistentIP Settings ● Redhat/CentOS:Redhat/CentOS: vi /etc/sysconfig/networkscripts/eth0vi /etc/sysconfig/networkscripts/eth0 # Intel Corporation 82545EM Gigabit Ethernet # Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)Controller (Copper) DEVICE=eth0DEVICE=eth0 BOOTPROTO=noneBOOTPROTO=none HWADDR=00:0c:29:05:e1:d2HWADDR=00:0c:29:05:e1:d2 IPADDR=163.16.5.180IPADDR=163.16.5.180 NETMASK=255.255.255.0NETMASK=255.255.255.0 ONBOOT=yesONBOOT=yes GATEWAY=163.16.5.254GATEWAY=163.16.5.254 TYPE=EthernetTYPE=Ethernet USERCTL=noUSERCTL=no IPV6INIT=noIPV6INIT=no PEERDNS=noPEERDNS=no
- 13. Persistent IP SettingsPersistentIP Settings ● Ubuntu:Ubuntu: vi /etc/network/interfacesvi /etc/network/interfaces auto loauto lo iface lo inet loopbackiface lo inet loopback iface eth0 inet staticiface eth0 inet static address 192.168.0.2address 192.168.0.2 netmask 255.255.255.0netmask 255.255.255.0
- 14. DHCP IP SettingsDHCPIP Settings ● Redhat/CentOS:Redhat/CentOS: vi /etc/sysconfig/networkscripts/eth0vi /etc/sysconfig/networkscripts/eth0 # Intel Corporation 82545EM Gigabit Ethernet # Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)Controller (Copper) DEVICE=eth0DEVICE=eth0 BOOTPROTO=dhcpBOOTPROTO=dhcp HWADDR=00:0c:29:05:e1:d2HWADDR=00:0c:29:05:e1:d2 ONBOOT=yesONBOOT=yes TYPE=EthernetTYPE=Ethernet USERCTL=yesUSERCTL=yes IPV6INIT=noIPV6INIT=no PEERDNS=yesPEERDNS=yes
- 15. DHCP IP SettingsDHCPIP Settings ● Ubuntu:Ubuntu: vi /etc/network/interfacesvi /etc/network/interfaces auto loauto lo iface lo inet loopbackiface lo inet loopback auto eth0auto eth0 iface eth0 inet dhcpiface eth0 inet dhcp
- 16. UsingUsing ifupifup andandifdownifdown ● Only to run while settings are stored inOnly to run while settings are stored in configuration fileconfiguration file – ifup eth0ifup eth0 Bring up interfaceBring up interface – ifdown eth0ifdown eth0 Shutdown interfaceShutdown interface
- 17. Configure Name ResolutionConfigureName Resolution ● /etc/hosts/etc/hosts – Static mappingStatic mapping 127.0.0.1 localhost.localdomain localhost127.0.0.1 localhost.localdomain localhost 192.168.0.1 server1.my.com server1192.168.0.1 server1.my.com server1 ● /etc/resolv.conf/etc/resolv.conf – DNS serverDNS server search my.comsearch my.com nameserver 192.168.0.1nameserver 192.168.0.1 nameserver 8.8.8.8nameserver 8.8.8.8
- 18. Configure Name ResolutionConfigureName Resolution ● /etc/nsswitch/etc/nsswitch – Resolving orderResolving order hosts: files dnshosts: files dns
- 19. Network Diagnostic ToolsNetworkDiagnostic Tools ● ping hostping host – Test connection availabilityTest connection availability – Common optionsCommon options c c nn : send: send nn packets onlypackets only w w nn : set dead line in: set dead line in nn secondsseconds
- 20. Network Diagnostic ToolsNetworkDiagnostic Tools ● traceroute hosttraceroute host – Display all routing nods in the routing pathDisplay all routing nods in the routing path – Common option:Common option: n n : Skip name resolving: Skip name resolving ● mtr hostmtr host – Advanced traceroute toolAdvanced traceroute tool
- 21. Network Diagnostic ToolsNetworkDiagnostic Tools ● arp -aarp -a – Display all entries in ARP cacheDisplay all entries in ARP cache ● arp IParp IP – Display specific entry in ARP cacheDisplay specific entry in ARP cache ● arp -d IParp -d IP – Delete an entryDelete an entry ● arp -s IP MACarp -s IP MAC – Set an entry manuallySet an entry manually
- 22. Network Diagnostic ToolsNetworkDiagnostic Tools ● host DOMAIN_NAME [DNS_SERVER]host DOMAIN_NAME [DNS_SERVER] – Lookup A record of a domain nameLookup A record of a domain name – Common optionsCommon options t t : query type: query type v v : verbose output: verbose output W W nn : time out in: time out in nn secondsseconds ● host IP [DNS_SERVER]host IP [DNS_SERVER] – The reverse DNS lookupThe reverse DNS lookup
- 23. Network Diagnostic ToolsNetworkDiagnostic Tools ● dig DOMAIN_NAME [@DNS_SERVER]dig DOMAIN_NAME [@DNS_SERVER] – Lookup domain name informationLookup domain name information – Common optionsCommon options x IP x IP : reverse lookup: reverse lookup +short +short : short answer: short answer +trace +trace : trace recursive lookup from root down: trace recursive lookup from root down
- 24. Network Diagnostic ToolsNetworkDiagnostic Tools ● whois DOMAIN_NAMEwhois DOMAIN_NAME – Lookup domain registration informationLookup domain registration information – Common optionsCommon options h server h server : specify whois server: specify whois server
- 25. Network Diagnostic ToolsNetworkDiagnostic Tools ● netstatnetstat – Display socket informationDisplay socket information – Common optionsCommon options n n : skip domain name lookup: skip domain name lookup l l : display listening server sockets: display listening server sockets t t : display TCP sockets: display TCP sockets u u : display UDP sockets: display UDP sockets a a : display all sockets: display all sockets p p : display PID, root only: display PID, root only