mirror of
https://github.com/vyos/vyos-documentation.git
synced 2025-10-26 08:41:46 +01:00
192 lines
6.2 KiB
ReStructuredText
192 lines
6.2 KiB
ReStructuredText
.. _high-availability:
|
|
|
|
High availability
|
|
=================
|
|
|
|
VRRP (Virtual Redundancy Protocol) provides active/backup redundancy for
|
|
routers. Every VRRP router has a physical IP/IPv6 address, and a virtual
|
|
address. On startup, routers elect the master, and the router with the highest
|
|
priority becomes the master and assigns the virtual address to its interface.
|
|
All routers with lower priorities become backup routers. The master then starts
|
|
sending keepalive packets to notify other routers that it's available. If the
|
|
master fails and stops sending keepalive packets, the router with the next
|
|
highest priority becomes the new master and takes over the virtual address.
|
|
|
|
VRRP keepalive packets use multicast, and VRRP setups are limited to a single
|
|
datalink layer segment. You can setup multiple VRRP groups
|
|
(also called virtual routers). Virtual routers are identified by a
|
|
VRID (Virtual Router IDentifier). If you setup multiple groups on the same
|
|
interface, their VRIDs must be unique, but it's possible (even if not
|
|
recommended for readability reasons) to use duplicate VRIDs on different
|
|
interfaces.
|
|
|
|
Basic setup
|
|
-----------
|
|
|
|
VRRP groups are created with the
|
|
``set high-availability vrrp group $GROUP_NAME`` commands. The required
|
|
parameters are interface, vrid, and virtual-address.
|
|
|
|
minimal config
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo vrid 10
|
|
set high-availability vrrp group Foo interface eth0
|
|
set high-availability vrrp group Foo virtual-address 192.0.2.1/24
|
|
|
|
You can verify your VRRP group status with the operational mode
|
|
``run show vrrp`` command:
|
|
|
|
.. code-block:: none
|
|
|
|
vyos@vyos# run show vrrp
|
|
Name Interface VRID State Last Transition
|
|
---------- ----------- ------ ------- -----------------
|
|
Foo eth1 10 MASTER 2s
|
|
|
|
IPv6 support
|
|
------------
|
|
|
|
The ``virtual-address`` parameter can be either an IPv4 or IPv6 address, but you
|
|
cannot mix IPv4 and IPv6 in the same group, and will need to create groups with
|
|
different VRIDs specially for IPv4 and IPv6.
|
|
|
|
Disabling a VRRP group
|
|
----------------------
|
|
|
|
You can disable a VRRP group with ``disable`` option:
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo disable
|
|
|
|
A disabled group will be removed from the VRRP process and your router will not
|
|
participate in VRRP for that VRID. It will disappear from operational mode
|
|
commands output, rather than enter the backup state.
|
|
|
|
Setting VRRP group priority
|
|
---------------------------
|
|
|
|
VRRP priority can be set with ``priority`` option:
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo priority 200
|
|
|
|
The priority must be an integer number from 1 to 255. Higher priority value
|
|
increases router's precedence in the master elections.
|
|
|
|
Sync groups
|
|
-----------
|
|
|
|
A sync group allows VRRP groups to transition together.
|
|
|
|
.. code-block:: none
|
|
|
|
edit high-availability vrrp
|
|
set sync-group MAIN member VLAN9
|
|
set sync-group MAIN member VLAN20
|
|
|
|
In the following example, when VLAN9 transitions, VLAN20 will also transition:
|
|
|
|
.. code-block:: none
|
|
|
|
vrrp {
|
|
group VLAN9 {
|
|
interface eth0.9
|
|
virtual-address 10.9.1.1/24
|
|
priority 200
|
|
vrid 9
|
|
}
|
|
group VLAN20 {
|
|
interface eth0.20
|
|
priority 200
|
|
virtual-address 10.20.20.1/24
|
|
vrid 20
|
|
}
|
|
sync-group MAIN {
|
|
member VLAN20
|
|
member VLAN9
|
|
}
|
|
}
|
|
|
|
|
|
.. warning:: All items in a sync group should be similarly configured.
|
|
If one VRRP group is set to a different premption delay or priority,
|
|
it would result in an endless transition loop.
|
|
|
|
|
|
Preemption
|
|
----------
|
|
|
|
VRRP can use two modes: preemptive and non-preemptive. In the preemptive mode,
|
|
if a router with a higher priority fails and then comes back, routers with lower
|
|
priority will give up their master status. In non-preemptive mode, the newly
|
|
elected master will keep the master status and the virtual address indefinitely.
|
|
|
|
By default VRRP uses preemption. You can disable it with the "no-preempt"
|
|
option:
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo no-preempt
|
|
|
|
You can also configure the time interval for preemption with the "preempt-delay"
|
|
option. For example, to set the higher priority router to take over in 180
|
|
seconds, use:
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo preempt-delay 180
|
|
|
|
Unicast VRRP
|
|
------------
|
|
|
|
By default VRRP uses multicast packets. If your network does not support
|
|
multicast for whatever reason, you can make VRRP use unicast communication
|
|
instead.
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo peer-address 192.0.2.10
|
|
set high-availability vrrp group Foo hello-source-address 192.0.2.15
|
|
|
|
Scripting
|
|
---------
|
|
|
|
VRRP functionality can be extended with scripts. VyOS supports two kinds of
|
|
scripts: health check scripts and transition scripts. Health check scripts
|
|
execute custom checks in addition to the master router reachability. Transition
|
|
scripts are executed when VRRP state changes from master to backup or fault and
|
|
vice versa and can be used to enable or disable certain services, for example.
|
|
|
|
Health check scripts
|
|
^^^^^^^^^^^^^^^^^^^^
|
|
|
|
This setup will make the VRRP process execute the
|
|
``/config/scripts/vrrp-check.sh script`` every 60 seconds, and transition the
|
|
group to the fault state if it fails (i.e. exits with non-zero status) three
|
|
times:
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo health-check script /config/scripts/vrrp-check.sh
|
|
set high-availability vrrp group Foo health-check interval 60
|
|
set high-availability vrrp group Foo health-check failure-count 3
|
|
|
|
Transition scripts
|
|
^^^^^^^^^^^^^^^^^^
|
|
|
|
Transition scripts can help you implement various fixups, such as starting and
|
|
stopping services, or even modifying the VyOS config on VRRP transition.
|
|
This setup will make the VRRP process execute the
|
|
``/config/scripts/vrrp-fail.sh`` with argument ``Foo`` when VRRP fails,
|
|
and the ``/config/scripts/vrrp-master.sh`` when the router becomes the master:
|
|
|
|
.. code-block:: none
|
|
|
|
set high-availability vrrp group Foo transition-script backup "/config/scripts/vrrp-fail.sh Foo"
|
|
set high-availability vrrp group Foo transition-script fault "/config/scripts/vrrp-fail.sh Foo"
|
|
set high-availability vrrp group Foo transition-script master "/config/scripts/vrrp-master.sh Foo"
|