FHRP Flashcards
First Hop Redundancy Protocols
What are the 3 FHRPs for the CCNA?
- HSRP (Hot Standby Router Protocol)
- VRRP (Virtual Router Redundancy Protocol)
- GLBP (Gateway Load Balancing Protocol)
What is an FHRP?
A protocol used to protect the default gateway of a subnet by allowing two or more routers to provide backup for that address
Two or more routers share a _____, and PCs configure this as their default gateway
VIP
Virtual IP
In addition to a VIP, two FHRP routers share a ____
VMAC, virtual MAC
How do routers determine their role in an FHRP protocol?
By sending multicast hello messages to eachother
How does an FHRP provide a host with the MAC of the active default gateway router?
By using ARP
The active router sends an ARP reply, while the standby ignores the message
How does an FHRP standby router change to an active router if the previous active router fails?
Gratuitous ARP
The new active router sends a gratuitous ARP message to broadcast, and all hosts update their MAC address for the default gateway IP to the new one.
When does an FHRP standby router change to an active?
After a standby router hasn’t received any hello messages for a duration of time.
By default 10 seconds, else 3 times the hello timer
What is a gratuitous ARP message?
An ARP reply sent without an ARP request triggering it. Sent broadcast.
By default, are FHRPs preemptive or non-preemptive
Non-preemptive by default
Which FHRP would use the VMAC 0000.5E00.0101?
VRRP
VRRP VMACs are of the form 0000.5E00.01xx, where the xx is the hex value of the group number.
Which FHRP would use the VMAC 0000.0C9F.F001
HSRP
HSRPv2 VMACs are of the form 0000.0C9F.Fxxx
Which FHRP would use the VMAC 0000.0C07.AC01
HSRP
HSRPv1 VMACs are of the form 0000.0C07.ACxx
What FHRP would use the VMAC 0007.B400.0101
GLBP
GLBP VMACs are of the form 0007.B400.xxyy, where xx is the GLBP group number, and yy is the AVF number
What FHRP would use the IP address 224.0.0.2
HSRPv1
What FHRP would use the IP address 224.0.0.102
HSRPv2
GLBP
Both use the same multicast IPv4, but GLBP uses a different port than HSRP
What FHRP would use the IP address 224.0.0.18
VRRP
What FHRP has a single active virtual gateway and up to 4 active virtual forwarders for a single group?
GLBP
Each AVF is assigned to a portion of hosts in the subnet by the AVG, therefore gateway traffic is load balanced across multiple devices
Routers in which HSRP states send hello messages?
Active, standby, speaking
Routers in which HSRP states listen for hello messages from the active router?
Standby, listening
Does HSRP support multiple routers in the standby state?
Technically no, but functionally yes
Only one router can have the standby state. If the active fails, the standby becomes the active, and then a new standby is elected from other routers in the listening state.
