###Common Network Utilities###
Features:
1. Find other hosts - PING
2. Check service availability | ability - Telnet
3. Network statistics - netstat
4. Interface configuration - ifconfig
5. Path to remote systems - traceroute, tracepath
6. Name resolutions - nslookup , dig, host, whois
Tasks:
1. Packet Internet Network Groper (PING) - Diagnostics Utility
a. ''ping hostname'' - sends an unlimited number of packets, by default
a1. ''ping -c 3 hostname'' - sends 3 packets to remote host
Note: PING generates ICMP echo-requests and expects ICMP echo-replies from the target
2. Telnet - tests availability of remote ports | also provides TTYs
a. ''telnet 192.168.75.1 80'' - checks connectivity to TCP:80
Note: You may test ports: 0-65535 || 2^16
3. Netstat
a. ''netstat -a'' - returns ALL sockets: UDP:TCP:Unix
b. ''netstat -nulp'' - reveals UDP listeners sans name resolution, but with programs/PIDs
c. ''netstat -ntlp'' - "" TCP ""
d. ''netstat -i'' - dumps active interfaces
e. ''netstat -rn'' - dumps routing table
4. Address Resolution Protocol (ARP) - translates between layer2 & layer3 addresses
Note: Every NIC contains a unique layer-2 MAC address
a. ''arp'' - dumps the ARP table
b. ''arp -n'' - excludes name resolution
c. ''arp -d IP'' - deletes entry from ARP table
Note: Arp will use the entry for your gateway when communicating with routed hosts
5. Traceroute - traces path between client & server || host-A & host-B
Supports multiple methods: ICMP, UDP, TCP
Uses ICMP TTL to determine number of hops between source and destination
Note: Initial ICMP TTL = 1 - for your default gateway
Note: After discerning default GW, traceroute increments ICMP TTL to 2.
Note: Default method is to use UDP:33434 & increment per hop found
Note: However, default method isn''t always fruitful. Try other methods: ICMP, TCP
a. ''traceroute 192.168.75.1'' - default route
b. ''traceroute www.linuxcbt.com''
ICMP TTL HOST Probe1 Probe2 Probe3
1 192.168.75.1 (192.168.75.1) 0.643 ms 0.471 ms 0.547 ms
2 bras11-l0.mrdnct.sbcglobal.net (204.60.4.47) 12.760 ms 14.205 ms 16.387 ms
c. ''tracepath www.linuxcbt.com'' - returns route and MTUs if possible
DIG - non-interactive
1. ''dig www.linuxcbt.com''
2. ''dig linuxcbt.com mx | ns'' - returns mx | ns records respectively
3. '' dig -x IP '' - reverses the query and returns the PTR record
Host - non-interactive
1. ''host www.linuxcbt.com'' - returns forward IP address
2. ''host -C linuxcbt.com'' returns SOA records
Whois - Searches for various objects: IPs, domains, etc.
1. ''whois linuxcbt.com''
###IPv4 Configurations###
Features:
1. Interface Configuration - ''ifconfig''
2. DHCP and/or Static Configuration support
3. Virtual (sub) interfaces - IPv4 aliases
4. Displays important metadata for various OSI layers, errors, diagnostics, etc.
Tasks:
1. ''ifconfig'' - dumps current configuration of active interfaces
Note: You should ALWAYS see the ''loopback'' interface
Note: ''gnome-nettool'' - provides ifconfig info., as well as various utilities
2. Use ''ifconfig'' to define a new IPv4 sub-interface of: eth0
a. ''ifconifg eth0:1 192.168.75.31'' - temporarily assigns the address for the uptime of the box
Note: Sub-interfaces allow applications, i.e. Apache, to bind services to them
3. Restart ''networking'' service and confirm interface availability
Note: temporary sub-interface survives restart of ''networking'' service, but NOT stop|start
4. Ensure that sub-interface persists reboots
a. ''/etc/network/interfaces'' - primary interface configuration file
''ping -I 192.168.75.32 ping 192.168.75.31''
5. Explore ALL interfaces:
a. ''ifconfig -a'' - enumerates ALL active | non-active interfaces
6. Remove interfaces:
a. ''ifconfig del eth0:1 192.168.75.31'' - removes for the session: eth0:1
b. ''ifconfig del eth0:2 192.168.75.32'' - removes for the session: eth0:2
###IPv6 Configuration###
Features:
1. Self-configuring
2. Based on 128-bit addresses, vs. 32-bit address space for: IPv4 approx. 4billion addresses
3. Enabled by default
4. Typically configured via router
5. Incorporates the MAC address of the connecting NIC
Note: MAC addresses use 48-bits
6. IPv6 addresses are subnetted with /64, which means: /64 for nets & /64 for hosts
Note: Routable IPv6 interfaces define by default a link-local address that is routable on the layer-2 broadcast domain (VLAN)
Note: Routable IPv6 interfaces will also auto-configure IPv6 addresses from edge devices: routers, firewalls, layer-3 switches
inet6 addr: fe80::20c:29ff:fe4d:e52c/64 Scope:Link
Note: IPv6 safely ignores leading zeroes
6-to-4 Address configured on router and distributed automatically:
6-to-4 Addresses include:
1. 2002 prefix - 48-bits
2. Embedded IPv4 routable address - 32-bits
3. MAC address of the host - 48-bits
inet6 addr: 2002:4687:db25:2:20c:29ff:fe4d:e52c/64 Scope:Global
Note: IPv6 address fully reveal your client''s, or NIC''s identity, as well as your IPv4 Internet presence if using 6-to-4 routing
Note: Edge devices, including DHCP6 servers, simply provide the IPv6 prefix. i.e. /64
