Hi there,
I want to share you the basic concepts of VRRP in this post. Hope it could help you understand VRRP more deeply.
About VRRP
The Virtual Router Redundancy Protocol (VRRP) groups multiple routing devices into a virtual router.
In this group,one device functions as the master, and the others as the backup.
When the next hop device of the master device fails, VRRP switches services to a backup device.
This implementation ensures nonstop service transmission and reliability.
VRRP terminology
VRRP router: Device running VRRP.
Virtual router: VRRP routers in one VRRP group will work cooperatively.VRRP generate a virtual router for this group,and it will be used as the default gateway on a LAN.
Virtual router master: VRRP device that forwards packets.
Virtual router backup: A group of VRRP devices that do not forward packets. When the master device is faulty, a backup device preempts to be the new master device.
VRID: virtual router ID.
VRRP terminology(cont.)
Virtual IP address: IP address of a virtual router. Virtual IP addresses are configurable.
Virtual MAC address: MAC address that is generated by the virtual router based on the virtual router ID. A virtual router has one virtual MAC address and is in the format of 00-00-5E-00-01-{VRID}(VRRP for IPv4) or 00-00-5E-00-02-{VRID}(VRRP for IPv6). The virtual router sends ARP Reply packets using the virtual MAC address instead of the interface MAC address
Priority: The virtual router selects the master and backup devices based on the priority.
What does master router do
Sends VRRP Advertisement packets at intervals.
Uses the virtual MAC address to respond to ARP Request packets destined for the virtual IP address.
Forwards IP packets destined for the virtual MAC address.
Processes the IP packets destined for the virtual IP address if the device is an IP address owner. If the device is not the IP address owner, it discards the IP packets destined for the virtual IP address.
Becomes the backup if the device receives a VRRP packet with a higher priority than the VRRP priority of the device.
Becomes the backup if the device receives a VRRP packet with the same priority as the VRRP priority of the device and the IP address of the local interface is smaller than the IP address of the connected interface on the remote device.
What does slave router do
Receives VRRP Advertisement packets from the master and determines whether the master works properly.
Does not respond to ARP Request packets destined for the virtual IP address.
Discards IP packets destined for the virtual IP address.
Resets the Master_Down_Interval timer and does not compare IP addresses if the received packet carries the same priority as the device or higher priority than the device.
Sets the Skew_time (offset time) if the device receives a VRRP packet with lower priority than the VRRP priority of the device and the packet priority is 0. Discards the packet with non-0 priority and becomes the master.
VRRP Packet
That's all for this post.
If you have any suggestions or questions about VRRP, kindly let me konw.
Thanks.
