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== ucarp :: Super Mini How To ==
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=== About ===
((http://www.ucarp.org/ UCARP)) allows a couple of hosts to share common virtual IP addresses in order
to provide automatic failover. It is a portable userland implementation of the
secure and patent-free Common Address Redundancy Protocol (CARP, OpenBSDΆs
alternative to the patents-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.
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=== Scenario ===
%%
+---------+ eth1 eth1 +----------+
| server1 |---------------- | server2 |
+---------+ +----------+
| (eth0) | (eth0)
| (eth0:1) |
| |
+--------------------------------------+
| | | switch | | |
+--------------------------------------+
|
|
|
+--------------------------------------+
| net |
+--------------------------------------+
%%
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=== Scripts ===
**cat /root/vip-up.sh**
%%
#! /bin/sh
/sbin/ip addr add 192.168.3.3/24 dev eth0
%%
**/root/vip-down.sh**
%%
#! /bin/sh
/sbin/ip addr del 192.168.3.3/24 dev eth0
%%
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=== Commands ===
**server1**
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ucarp -i eth1 -s 192.168.3.1 -v 1 --pass=mypassword -a 192.168.3.3 -P -u /root/vip-up.sh -d vip-down.sh
%%
**server2**
%%
ucarp -i eth1 -s 192.168.3.2 -v 1 --pass=mypassword -a 192.168.3.3 -u /root/vip-up.sh -d vip-down.sh
%%
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