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+---
+lastproofread: '2021-06-30'
+---
+
+(high-availability)=
+
+# High availability
+
+VRRP (Virtual Router 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 if they use the same address family,
+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 address.
+
+minimal config
+
+```none
+set high-availability vrrp group Foo vrid 10
+set high-availability vrrp group Foo interface eth0
+set high-availability vrrp group Foo address 192.0.2.1/24
+```
+
+You can verify your VRRP group status with the operational mode
+`run show vrrp` command:
+
+```none
+vyos@vyos# run show vrrp
+Name        Interface      VRID  State    Last Transition
+----------  -----------  ------  -------  -----------------
+Foo         eth1             10  MASTER   2s
+```
+
+## IPv6 support
+
+The `address` parameter can be either an IPv4 or IPv6 address, but you can
+not mix IPv4 and IPv6 in the same group, and will need to create groups with
+different VRIDs specially for IPv4 and IPv6.
+If you want to use IPv4 + IPv6 address you can use option `excluded-address`
+
+## Address
+
+The `address` can be configured either on the VRRP interface or on not VRRP
+interface.
+
+```none
+set high-availability vrrp group Foo address 192.0.2.1/24
+set high-availability vrrp group Foo address 203.0.113.22/24 interface eth2
+set high-availability vrrp group Foo address 198.51.100.33/24 interface eth3
+```
+
+## Disabling a VRRP group
+
+You can disable a VRRP group with `disable` option:
+
+```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.
+
+## Exclude address
+
+Exclude IP addresses from `VRRP packets`. This option `excluded-address` is
+used when you want to set IPv4 + IPv6 addresses on the same virtual interface
+or when used more than 20 IP addresses.
+
+```none
+set high-availability vrrp group Foo excluded-address '203.0.113.254/24'
+set high-availability vrrp group Foo excluded-address '2001:db8:aa::1/64'
+set high-availability vrrp group Foo excluded-address '2001:db8:22::1/64'
+```
+
+## Setting VRRP group priority
+
+VRRP priority can be set with `priority` option:
+
+```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.
+
+```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:
+
+```none
+vrrp {
+    group VLAN9 {
+        interface eth0.9
+        address 10.9.1.1/24
+        priority 200
+        vrid 9
+    }
+    group VLAN20 {
+        interface eth0.20
+        priority 200
+        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 preemption 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:
+
+```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:
+
+```none
+set high-availability vrrp group Foo preempt-delay 180
+```
+
+## Track
+
+Track option to track non VRRP interface states. VRRP changes status to
+`FAULT` if one of the track interfaces in state `down`.
+
+```none
+set high-availability vrrp group Foo track interface eth0
+set high-availability vrrp group Foo track interface eth1
+```
+
+Ignore VRRP main interface faults
+
+```none
+set high-availability vrrp group Foo track exclude-vrrp-interface
+```
+
+## 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.
+
+```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
+```
+
+## rfc3768-compatibility
+
+RFC 3768 defines a virtual MAC address to each VRRP virtual router.
+This virtual router MAC address will be used as the source in all periodic VRRP
+messages sent by the active node. When the rfc3768-compatibility option is set,
+a new VRRP interface is created, to which the MAC address and the virtual IP
+address is automatically assigned.
+
+```none
+set high-availability vrrp group Foo rfc3768-compatibility
+```
+
+Verification
+
+```none
+$show interfaces ethernet eth0v10
+eth0v10@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
+state UP group default qlen 1000
+link/ether 00:00:5e:00:01:0a brd ff:ff:ff:ff:ff:ff
+inet 172.25.0.247/16 scope global eth0v10
+valid_lft forever preferred_lft forever
+```
+
+:::{warning}
+RFC 3768 creates a virtual interface. If you want to apply
+the destination NAT rule to the traffic sent to the virtual MAC, set
+the created virtual interface as `inbound-interface`.
+:::
+
+## Global options
+
+On most scenarios, there's no need to change specific parameters, and using
+default configuration is enough. But there are cases were extra configuration
+is needed.
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters startup_delay <1-600>
+
+   This option specifies a delay in seconds before vrrp instances start up
+   after keepalived starts.
+```
+
+## Gratuitous ARP
+
+These configuration is not mandatory and in most cases there's no
+need to configure it. But if necessary, Gratuitous ARP can be configured in
+`global-parameters` and/or in `group` section.
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters garp interval
+   <0.000-1000>
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp group <name> garp interval <0.000-1000>
+
+   Set delay between gratuitous ARP messages sent on an interface.
+
+   0 if not defined.
+```
+
+% stop_vyoslinter
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters garp master-delay <1-255>
+```
+
+% start_vyoslinter
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp group <name> garp master-delay <1-255>
+
+   Set delay for second set of gratuitous ARPs after transition to MASTER.
+
+   5 if not defined.
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters garp master-refresh
+   <1-600>
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp group <name> garp master-refresh
+   <1-600>
+
+   Set minimum time interval for refreshing gratuitous ARPs while MASTER.
+
+   0 if not defined, which means no refreshing.
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters garp
+   master-refresh-repeat <1-600>
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp group <name> garp
+   master-refresh-repeat <1-600>
+
+   Set number of gratuitous ARP messages to send at a time while MASTER.
+
+   1 if not defined.
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters garp master-repeat
+   <1-600>
+```
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp group <name> garp master-repeat
+   <1-600>
+
+   Set number of gratuitous ARP messages to send at a time after transition to
+   MASTER.
+
+   5 if not defined.
+```
+
+## Version
+
+```{eval-rst}
+.. cfgcmd:: set high-availability vrrp global-parameters version 2|3
+
+   Set the default VRRP version to use. This defaults to 2, but IPv6 instances
+   will always use version 3.
+```
+
+## 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.
+
+:::{note}
+Simply placing script files in `/config/scripts/` does not mean the
+system can execute them. To make custom scripts executable, grant them
+**execute permissions**. Use the following command:
+
+```none
+chmod +x /config/scripts/script-name.sh
+```
+:::
+
+:::{warning}
+It is not recommended to change VRRP configuration
+inside health-check and transition scripts.
+:::
+
+### Health check scripts
+
+There is the ability to run an arbitrary script at regular intervals
+according to health-check parameters. If a script returns 0, it
+indicates success. If a script returns anything else, it will indicate
+that the VRRP instance should enter the FAULT state.
+
+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:
+
+% stop_vyoslinter
+
+```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
+```
+
+% start_vyoslinter
+
+An optional `timeout` can be set to define the maximum number of seconds the
+script is allowed to run. This is useful for scripts that may hang or take
+longer than expected — setting the timeout higher than the interval allows
+longer-running scripts to complete before being considered failed.
+
+% stop_vyoslinter
+
+```none
+set high-availability vrrp group Foo health-check script /config/scripts/vrrp-check.sh
+set high-availability vrrp group Foo health-check interval 20
+set high-availability vrrp group Foo health-check failure-count 3
+set high-availability vrrp group Foo health-check timeout 40
+```
+
+% start_vyoslinter
+
+When the vrrp group is a member of the sync group will use only
+the sync group health check script.
+This example shows how to configure it for the sync group:
+
+% stop_vyoslinter
+
+```none
+set high-availability vrrp sync-group Bar health-check script /config/scripts/vrrp-check.sh
+set high-availability vrrp sync-group Bar health-check interval 60
+set high-availability vrrp sync-group Bar health-check failure-count 3
+```
+
+% start_vyoslinter
+
+### 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:
+
+% stop_vyoslinter
+
+```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"
+```
+
+% start_vyoslinter
+
+To know more about scripting, check the {ref}`command-scripting` section.
+
+## Virtual-server
+
+```{eval-rst}
+.. include:: /_include/need_improvement.txt
+```
+
+Virtual Server allows to Load-balance traffic destination virtual-address:port
+between several real servers.
+
+### Algorithm
+
+Load-balancing schedule algorithm:
+
+- round-robin
+- weighted-round-robin
+- least-connection
+- weighted-least-connection
+- source-hashing
+- destination-hashing
+- locality-based-least-connection
+
+```none
+set high-availability virtual-server 203.0.113.1 algorithm 'least-connection'
+```
+
+### Forward method
+
+- NAT
+- direct
+- tunnel
+
+```none
+set high-availability virtual-server 203.0.113.1 forward-method 'nat'
+```
+
+### Health-check
+
+Custom health-check script allows checking real-server availability
+
+% stop_vyoslinter
+
+```none
+set high-availability virtual-server 203.0.113.1 real-server 192.0.2.11 health-check script <path-to-script>
+```
+
+% start_vyoslinter
+
+### Fwmark
+
+Firewall mark. It possible to loadbalancing traffic based on `fwmark` value
+
+```none
+set high-availability virtual-server 203.0.113.1 fwmark '111'
+```
+
+### Real server
+
+Real server IP address and port
+
+% stop_vyoslinter
+
+```none
+set high-availability virtual-server 203.0.113.1 real-server 192.0.2.11 port '80'
+```
+
+% start_vyoslinter
+
+### Example
+
+Virtual-server can be configured with VRRP virtual address or without VRRP.
+
+In the next example all traffic destined to `203.0.113.1` and port `8280`
+protocol TCP is balanced between 2 real servers `192.0.2.11` and
+`192.0.2.12` to port `80`
+
+Real server is auto-excluded if port check with this server fail.
+
+% stop_vyoslinter
+
+```none
+set interfaces ethernet eth0 address '203.0.113.11/24'
+set interfaces ethernet eth1 address '192.0.2.1/24'
+set high-availability vrrp group FOO interface 'eth0'
+set high-availability vrrp group FOO no-preempt
+set high-availability vrrp group FOO priority '150'
+set high-availability vrrp group FOO address '203.0.113.1/24'
+set high-availability vrrp group FOO vrid '10'
+
+set high-availability virtual-server 203.0.113.1 algorithm 'source-hashing'
+set high-availability virtual-server 203.0.113.1 delay-loop '10'
+set high-availability virtual-server 203.0.113.1 forward-method 'nat'
+set high-availability virtual-server 203.0.113.1 persistence-timeout '180'
+set high-availability virtual-server 203.0.113.1 port '8280'
+set high-availability virtual-server 203.0.113.1 protocol 'tcp'
+set high-availability virtual-server 203.0.113.1 real-server 192.0.2.11 port '80'
+set high-availability virtual-server 203.0.113.1 real-server 192.0.2.12 port '80'
+```
+
+% start_vyoslinter
+
+A firewall mark `fwmark` allows using multiple ports for high-availability
+virtual-server.
+It uses fwmark value.
+
+In this example all traffic destined to ports "80, 2222, 8888" protocol TCP
+marks to fwmark "111" and balanced between 2 real servers.
+Port "0" is required if multiple ports are used.
+
+% stop_vyoslinter
+
+```none
+set interfaces ethernet eth0 address 'dhcp'
+set interfaces ethernet eth0 description 'WAN'
+set interfaces ethernet eth1 address '192.0.2.1/24'
+set interfaces ethernet eth1 description 'LAN'
+
+set policy route PR interface 'eth0'
+set policy route PR rule 10 destination port '80,2222,8888'
+set policy route PR rule 10 protocol 'tcp'
+set policy route PR rule 10 set mark '111'
+
+set high-availability virtual-server vyos fwmark '111'
+set high-availability virtual-server vyos protocol 'tcp'
+set high-availability virtual-server vyos real-server 192.0.2.11 health-check script '/config/scripts/check-real-server-first.sh'
+set high-availability virtual-server vyos real-server 192.0.2.11 port '0'
+set high-availability virtual-server vyos real-server 192.0.2.12 health-check script '/config/scripts/check-real-server-second.sh'
+set high-availability virtual-server vyos real-server 192.0.2.12 port '0'
+
+set nat source rule 100 outbound-interface name 'eth0'
+set nat source rule 100 source address '192.0.2.0/24'
+set nat source rule 100 translation address 'masquerade'
+```
+
+% start_vyoslinter
+
+Op-mode check virtual-server status
+
+```none
+vyos@r14:~$ run show virtual-server
+IP Virtual Server version 1.2.1 (size=4096)
+Prot LocalAddress:Port Scheduler Flags
+  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
+FWM  111 lc persistent 300
+  -> 192.0.2.11:0                 Masq    1      0          0
+  -> 192.0.2.12:0                 Masq    1      1          0
+```
+