1.5.1 GPL (GNU General Public License)    
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UCARP allows a couple of hosts to share common virtual IP addresses in order to provide automatic failover.






UCARP allows a couple of hosts to share common virtual IP addresses in order to provide automatic failover.

UCARP project is a portable userland implementation of the secure and patent-free Common Address Redundancy Protocol (CARP, OpenBSD's alternative to the atents-bloated VRRP).

Strong points of the CARP protocol are: very low overhead, cryptographically
signed messages, interoperability between different operating systems and no need for any dedicated extra network link between redundant hosts.


The `configure' shell script attempts to guess correct values for various system-dependent variables used during compilation.

It uses those values to create a `Makefile' in each directory of the package. It may also create one or more `.h' files containing system-dependent definitions.

Finally, it creates a shell script `config.status' that you can run in the future to recreate the current configuration, and a file `config.log' containing compiler output (useful mainly for debugging `configure').

It can also use an optional file (typically called `config.cache' and enabled with `--cache-file=config.cache' or simply `-C') that saves the results of its tests to speed up reconfiguring. (Caching is disabled by default to prevent problems with accidental use of stale cache files.)

If you need to do unusual things to compile the package, please try to figure out how `configure' could check whether to do them, and mail diffs or instructions to the address given in the `README' so they can be considered for the next release.

If you are using the cache, and at some point `config.cache' contains results you don't want to keep, you may remove or edit it.

The file `configure.ac' (or `configure.in') is used to create `configure' by a program called `autoconf'. You only need `configure.ac' if you want to change it or regenerate `configure' using a newer version of `autoconf'.

The simplest way to compile this package is:

1. `cd' to the directory containing the package's source code and type `./configure' to configure the package for your system.

If you're using `csh' on an old version of System V, you might need to type `sh ./configure' instead to prevent `csh' from trying to execute `configure' itself.

Running `configure' takes awhile. While running, it prints some messages telling which features it is checking for.

2. Type `make' to compile the package.

3. Optionally, type `make check' to run any self-tests that come with the package.

4. Type `make install' to install the programs and any data files and documentation.

5. You can remove the program binaries and object files from the source code directory by typing `make clean'.

To also remove the files that `configure' created (so you can compile the package for a different kind of computer), type `make distclean'. There is also a `make maintainer-clean' target, but that is intended mainly for the package's developers.

If you use it, you may have to get all sorts of other programs in order to regenerate files that came with the distribution.


A couple of virtual hosts must be given:

- A shared virtual IP, which will be dynamically answered by one alive host.
Services that need high availability need to be assigned to that virtual IP.

- A real IP address for each host.

- A shared identifier for the virtual IP address, which is a number between 1
and 255.

- For each host : an advertisement time base and skew, which is the frequency
the host will tell the other one that it's still alive. By default, base is 1 and skew is 0, which basically means one advertisement a second.

The protocol is very light, a tiny packet every second won't have any noticeable impact on your network.

- A shared password (that will never go plaintext to the network).

- A script to bring the virtual address up when a host becomes the master.

- Another script to bring the virtual address down when a host is no more the master.
Last updated on May 28th, 2009
UCARP - screenshot #1

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