Networking
**********

Links
=====

- `Top 5 unix network monitoring utilities`_

Gateway
=======

To find the IP address of your network gateway::

  $ route -n
  Kernel IP routing table
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  192.168.11.0    0.0.0.0         255.255.255.0   U     0      0        0 br0
  192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
  169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 br0
  0.0.0.0         192.168.11.1    0.0.0.0         UG    100    0        0 br0

Check the line with the ``UG`` flag ``U`` indicates that route is up and ``G``
indicates that it is gateway.

The following command will produce very similar output::

  netstat -nr

DNS
===

The DNS server should be listed in::

  /etc/resolv.conf

`To view the DNS configuration of a Windows workstation`_.

Lookup
------

To lookup the DNS information for a site (including IP address)::

  dig news.bbc.co.uk

IP
==

To find the IP address::

  ifconfig

To set the IP address, edit the following files::

  /etc/network/interfaces
  /etc/resolv.conf

hosts
=====

The file::

  /etc/hosts

Is normally used in preference to a DNS server.  The file is used by the
workstation to lookup the IP address for a server and to find the fully
qualified name from an alias.

The fully qualified domain name needs to be entered.  To leave it out would
imply some kind of DNS search as a command would not know if this was a top
level domain or a host on the local network.

An example file::

  127.0.0.1       woody.pjdk.co.uk    woody        localhost.localdomain   localhost
  10.10.10.4      weezy.pjdk.co.uk    weezy
  10.10.10.5      buzz.pjdk.co.uk     buzz

Another example file::

  127.0.0.1>--localhost
  127.0.1.1>--buzz

  192.168.11.68   bigbox
  192.168.11.69   toybox
  192.168.11.73   storagebox
  192.168.11.70   openerp-dev

  # The following lines are desirable for IPv6 capable hosts
  ::1     ip6-localhost ip6-loopback
  fe00::0 ip6-localnet
  ff00::0 ip6-mcastprefix
  ff02::1 ip6-allnodes
  ff02::2 ip6-allrouters
  ff02::3 ip6-allhosts

``host`` is a simple utility for performing DNS lookups.  It is normally
used to convert names to IP addresses and vice versa::

  host mail.yahoo.com

NFS
===

- :doc:`nfs`

nmap
====

To see which ports are open on a server::

  nmap <ip address>

e.g::

  nmap 10.10.10.4

telnet
======

To see if a port is running a service::

  telnet <ip address> <port>

e.g::

  telnet 10.10.10.4 80

Probably have to close down the telnet window (I don't know how to close it
properly).


.. _`Top 5 unix network monitoring utilities`: http://immike.net/blog/2007/05/01/top-5-unix-network-monitoring-utilities/
.. _`To view the DNS configuration of a Windows workstation`: ../windows/network.html