# Miscellany

This appendix is a collection of odds and ends which didn't fit anyplace else. So, consider it a grab-bag of toys, tips, and remarks. Here, you'll find a brief look at some IP calculators and some general remarks about iproute2 tools.

## `ipcalc` and other IP addressing calculators

There are a number of different utilities called ipcalc, almost all of which perform the same basic task. These are handy calculators for converting from CIDR to traditional IP notation and determining network and broadcast addresses.

- A short perl script, this prints out alll the information you would want to know about an IP address. It defaults to print colorized output, and comes with its own CGI (shown running here).

- For those who perform all operations and research through a web browser, a DHTML calculator should do the trick.

- And here's another IP calculator.

- You can run this ipcalc, which features hexadecimal as well as decimal output, on your PDA.

- RedHat has created their own `ipcalc` utility which prints out a shell variable assignment command instead of simply the requested piece of information. In the startup scripts, RedHat evals this variable assignement into existence. Despite this shortcoming, it is a useful tool and is documented in its manpage (part of the initscripts RPM).

Doubtless, there are a large number of other IP calculators available to ease the job of the network administrator. The above tools are meant as a brief summary of some of the offerings.

## Some general remarks about &iproute2; tools

This is a meant to be a collected set of thoughts which don't fit anyplace else about the &iproute2; tools. If you are reading this in search of more details about the &iproute2; tools, you should run (not walk) to your nearest command line, and execute the following command: `bash -c ' gv $( locate ip-cref.ps ) '`.

In any case, I suggest that the reader consult the documentation which comes with the &iproute2; package for canonical answers.

- The &iproute2; suite exposes all of the networking functionality of the linux kernel where the venerable tools (`ifconfig`, `route`) are hamstrung by history.

- Each of the &iproute2; object names can be shortened to the shortest unique set of characters. This means that `ip route show` can be abbreviated `ip ro s` and `ip rule show` can be abbreviated `ip ru s`. Also `ip address show` can be `ip a s`. Such convenient shortcuts on the command line are often confusing in documentation. For this reason, I have preferred examples featuring the complete object names and action verbs. Note also below that &iproute2; accepts not only abbreviations but also synonyms as described in .

- There are some syntactic synonyms available within the &iproute2; package. See this for a complete list of synonyms.

- Because the &iproute2; command suite is under development, there may be slight differences between the output described in this documentation and that of your release of &iproute2;. I have tried to focus on the overwhelmingly common uses of the &iproute2; tools rather than the ones which are under active development, and are subject to syntactic changes or new output presentations.

- There are extensions to the &iproute2; command suite, which can alter the sets of objects or syntax available for manipulation and inspection. Where these are covered in detail in this documentation, they will be relegated to a non-canonical ghetto. Examples will (someday) include `ip arp` and `tc` extensions.

There are some common synonyms in &iproute2; syntax. Outlined below in is a list of the common synonyms. Note, that these synonyms are available in addition to the abbreviations indicated above.

### &iproute2; Synonyms

Command Variant | Synonyms
--- | ---
`ip neighbor` | `ip neighbour`
`ip tunnel` | `ip tunl`
`ip OBJECT show` | `ip OBJECT ls`, `ip OBJECT list`
`ip OBJECT change` | `ip OBJECT chg`, `ip OBJECT replace`

Because the &iproute2; suite of tools is so tightly integrated with linux, it is not available for other operating systems. This is at once its strength and weakness. For users contemplating linux for the first time, `ifconfig`, `netstat`, and `route` are familiar and they feel intuitive. More experienced users and control freaks will find the &iproute2; tools attractive and perhaps indispensable.

## Brief introduction to `sysctl`

Many behaviours of the linux kernel can be modified through the use of run time variables. These variables can be changed manually or with the use of a convenient command line utility. Most linux distributions also include a standard configuration file which can store these parameters for use at boot time.

For a deeper reference into the matter and use of `sysctl` see the IP Sysctl tutorial, maintained by Oskar Andreasson.