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In IPv6 networks, hosts learn about routers by receiving Router Advertisements used by the Neighbor Discovery (ND) protocol. ND already has a built-in mechanism to determine unreachable routers. However, it can take up to 38 seconds to detect an unreachable router. It is possible to change parameters and make detection faster, but it will increase the overhead of ND traffic especially if there are a lot of hosts. VRRP allows detecting the detection of unreachable routers within 3 seconds without additional traffic overhead.

Virtual Router Redundancy Protocol (VRRP) provides a solution by combining a number of routers into a logical group called Virtual Router (VR). VRRP implementation in RouterOS is based on VRRPv2 RFC 3768 and VRRPv3 RFC 5798.

It is recommended to use the same version of RouterOS for all devices with the same VRID used to implement VRRP.

Note

 According to RFC authentication is deprecated for VRRP v3

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  • responds to ND Neighbor Solicitation message for the associated IPv6 address;
  • sends ND Router Advertisements for the associated IPv6 addresses.


If the advertisement packet is received by master node:

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Connection tracking entries are synchronized only from the Master to the Backup device.

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When both sync-connection-tracking and preemption-mode are enabled, and a router with higher VRRP priority becomes online, the connections get synchronized first, and only then the router with higher priority becomes the VRRP master.

Tip

If multiple VRRP interfaces are configured between two units, then it is enough to enable sync-connection-tracking=yes on one (=yes on one (preferably master) VRRP interface.

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PropertyDescription
arp (disabled | enabled | proxy-arp | reply-only; Default: enabled)ARP resolution protocol mode
arp-timeout(integer; Default: auto)
authentication (ah | none | simple; Default: none)Authentication method to use for VRRP advertisement packets.
  • none - should be used only in low-security networks (e.g., two VRRP nodes on LAN).
  • ah - IP Authentication Header. This algorithm provides strong protection against configuration errors, replay attacks, and packet corruption/modification. Recommended when there is limited control over the administration of nodes on a LAN. HMAC-MD5 is used.
  • simple - uses a clear-text password. Protects against accidental misconfiguration of routers on a local network.
group-master authority (interface; Default: none)

Allows combining multiple VRRP interfaces to maintain the same VRRP status within the group. For example, VRRP instances run on LAN and WAN networks with NAT in-between. If one VRRP instance is Master and the other is Backup on the same device, the entire network malfunctions due to NAT failure. Grouping LAN and WAN VRRP interfaces ensure ensures that both are either VRRP Master or Backup.

In a VRRP group, VRRP control traffic gets sent only by the group masterauthority. That's why in a typical WAN+LAN setup, it is recommended to use the LAN network as the group master to keep VRRP control traffic in the internal network.

Code Block
languageros
/interface vrrp
add name=vrrp-wan interface=sfp-sfpplus1 vrid=1 priority=100
add name=vrrp-lan interface=bridge1 vrid=2 priority=100
set [find] group-master=vrrp-lan
set [find] group-authority=vrrp-lan

Group-authority was previously called "group-master", "group-master" is kept for compatibility with scripts, but if both are set only "group-authority" will be taken into account.

interface (string; Default: )Interface name on which VRRP instance will be running
interval (time [10ms..4m15s]; Default: 1s)VRRP update interval in seconds. Defines how often the master sends advertisement packets.
mtu (integer; Default: 1500)Layer3 MTU size. Since RouterOS v7.7, the VRRP interface always uses slave interface MTU
name (string; Default: )VRRP interface name
on-backup (string; Default: )Script to execute when the node is switched to the backup state
on-master (string; Default: )Script to execute when the node is switched to master state
on-fail (string; Default: )Script to execute when the node fails
password (string; Default: )Password required for authentication. Can be ignored if authentication is not used.
preemption-mode (yes | no; Default: yes)Whether the master node always has the priority. When set to 'no' the backup node will not be elected to be a master until the current master fails, even if the backup node has higher priority than the current master. This setting is ignored if the owner router becomes available
priority (integer: 1..254; Default: 100)Priority of VRRP node used in Master election algorithm. A higher number means higher priority. '255' is reserved for the router that owns VR IP and '0' is reserved for the Master router to indicate that it is releasing responsibility.
remote-address (IPv4; Default: )

Specifies the remote address of the other VRRP router for syncing connection tracking. If not set, the system autodetects the remote address via VRRP. The remote address is used only if sync-connection-tracking=yes. Explicitly setting a remote address has the following benefits:

  • Connection syncing starts faster since there is no need to wait for VRRP's initial message exchange to detect the remote address.
  • Faster VRRP Master election.
  • Allows sending connection tracking data via a different network interface (e.g., a dedicated secure line between two routers).

Sync connection tracking uses UDP port 8275.

v3-protocol (ipv4 | ipv6; Default: ipv4)A protocol that will be used by VRRPv3. Valid only if the version is 3.
version (integer [2, 3]; Default: 3)Which VRRP version to use.
vrid (integer: 1..255; Default: 1)Virtual Router identifier. Each Virtual router must have a unique id number
sync-connection-tracking(string; Default: no)Synchronize connection tracking entries from Master to Backup device. The VRRP connection tracking synchronization requires that RouterOS connection tracking is running.

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