Other - FHRP Concepts Flashcards
(5 cards)
What are the limitations of default gateways?
In a switched network, the end device is configured with a single default gateway.
If that default gateway cannot be reached, the end device is unable to send packets off the local network.
What is router redundancy? How does it work?
Multiple routers work together to act like one virtual router.
They share one IP address and MAC address, so your devices only see a single gateway.
If the main router fails, another router takes over automatically without users noticing.
Devices send data to the virtual router. One physical router is active and does the actual forwarding. Others are standby and ready to take over if needed. This process is controlled by a redundancy protocol, like HSRP, VRRP, or GLBP.
What happens during router failover?
- The standby router stops seeing hello messages from the forwarding router.
- The standby router assumes the role of the forwarding router.
- Because the new forwarding router assumes both the IPv4 and MAC addresses of the virtual router, the host devices see no disruption in service.
How is the role of active and standby routers determined?
By default, the router with the numerically highest IPv4 address is elected as the active router.
However, it is better to control HSRP election with priority, instead of relying on the highest address.
What is Hot Standby Router Protocol (HSRP) pre-emption?
Pre-emption is the ability of an HSRP router to trigger the re-election process.
By default, after a router becomes the active router, it will remain the active router even if another router comes online with a higher HSRP priority.
To force a new HSRP election process to take place when a higher priority router comes online, pre-emption must be enabled.
With pre-emption disabled, the router that boots up first will become the active router if there are no other routers online during the election process.
