What is VRRP ?
What is VRRP ?
VRRP (Virtual Router Redundancy Protocol) is a standardized protocol comparable to HSRP (Hot Standby Routing Protocol) that enables the establishment of a virtual gateway. It permits LAN hosts to utilize local redundant routing frameworks by configuring a single static default route on the hosts. This approach is commonly implemented across various Ethernet types, such as fast, gigabit, and 10-gigabit, as well as logical interfaces set up in active/passive or primary/backup configurations.
How VRRP Works ?
Due to its simplicity and support for high availability, a VRRP group can accommodate up to 255 devices. While VRRP automatically assigns priority among compatible devices, administrators have the option to manually set priority levels ranging from 1 (lowest) to 255 (highest) for each device.
This setup leads to several outcomes. Primarily, if the current primary router fails, the system selects a new primary based on priority. Additionally, if a VRRP router with a higher priority than the existing primary joins the network, it can take over as the primary router. However, this is not always guaranteed, as it is also possible to disregard a higher-priority router and maintain the original primary as the preferred backup.
Lets go through the Process
- The system allocates a virtual IP address from the local subnet, which serves as the default gateway for all local hosts.
- The virtual MAC address is automatically generated using the last eight bytes of the VRRP hexadecimal group number. By default, VRRP employs the 0000.5e00.01xx MAC address format, where the final two digits are replaced with the group’s hex number.
- Within a VRRP group, the member with the highest priority becomes the primary device and starts forwarding traffic. If two members share the same priority, the device with the higher IP address is given precedence.
- All other VRRP devices function as backups.
- The primary router sends multicast keep-alive messages to backup devices every second.
- If a backup router does not receive the master advertisement within a specified timeframe, it assumes the role of primary router through the preempt function.
- The VRRP group continuously monitors object status changes, enabling dynamic priority adjustments and primary device selection.
- Authentication options supported by VRRP include plain-text, MD5, or no authentication.
