Cisco CCNA Preparation · lesson 20 of 36 · 25 min
The Default Gateway Problem
End devices are configured with a single default gateway. If that gateway router fails, all traffic off the local subnet stops — even if a backup router exists. First-Hop Redundancy Protocols (FHRPs) solve this by presenting a virtual IP and MAC address shared between two or more routers. End devices point to the virtual IP; if the active router fails, the standby takes over transparently.
FHRP Comparison
HSRP Deep Dive
HSRP (Hot Standby Router Protocol) is the most tested FHRP on the CCNA. One router is Active (forwards traffic), one is Standby (monitors active, ready to take over). Both share a virtual IP and virtual MAC (0000.0C07.ACxx where xx = group number in hex).
Preemption
By default, if the active router recovers after a failure, it does NOT reclaim the active role. Enable preempt so the higher-priority router automatically becomes active again when it comes back online.
Flashcard Drill
FHRP First-Hop Redundancy Protocol — provides a virtual gateway IP shared between routers for default gateway redundancy. HSRP Hot Standby Router Protocol — Cisco proprietary FHRP. Active/Standby model. VRRP Virtual Router Redundancy Protocol — IEEE open standard FHRP. Master/Backup model. GLBP Gateway Load Balancing Protocol — Cisco proprietary, supports active/active load balancing. HSRP Active The router currently forwarding traffic for the virtual IP. HSRP Standby The backup router monitoring the active — takes over if active fails. HSRP preempt Allows higher-priority router to reclaim active role after recovering from failure. HSRP virtual MAC 0000.0C07.ACxx — where xx is the HSRP group number in hex. show standby brief Verifies HSRP state, virtual IP, active/standby routers, and priority. HSRP priority Default 100 — higher priority wins active role. Tie broken by highest IP.
Knowledge Check
First-Hop Redundancy — 10 Questions
What problem do FHRPs solve?
- Routing loops
- Default gateway single point of failure
- VLAN mismatches
- Switching loops
Answer: Default gateway single point of failure
FHRPs provide a virtual gateway IP shared between routers — if the active router fails, the standby takes over.
Which FHRP is an open IEEE standard?
- HSRP
- GLBP
- VRRP
- PVST
Answer: VRRP
VRRP (IEEE 802.3) is the open standard FHRP. HSRP and GLBP are Cisco proprietary.
In HSRP, which router forwards traffic for the virtual IP?
- Standby
- Active
- Master
- Primary
Answer: Active
The HSRP Active router forwards traffic. The Standby monitors and takes over if Active fails.
The HSRP command to allow a higher-priority router to reclaim the active role after recovery is standby 1 _____.
Answer: preempt
standby 1 preempt enables preemption — the higher-priority router automatically becomes active when it recovers.
What is the default HSRP priority?
- 50
- 100
- 110
- 255
Answer: 100
Default HSRP priority is 100. Higher priority wins the active role.
Which FHRP supports active/active load balancing across multiple routers?
- HSRP
- VRRP
- GLBP
- STP
Answer: GLBP
GLBP (Gateway Load Balancing Protocol) allows multiple routers to simultaneously forward traffic.
HSRP preemption is enabled by default.
- True
- False
Answer: False
HSRP preemption is disabled by default — you must explicitly configure standby 1 preempt.
Which command verifies HSRP state and virtual IP?
- show ip route
- show standby brief
- show interfaces
- show ip ospf neighbor
Answer: show standby brief
show standby brief shows HSRP group, state (Active/Standby), virtual IP, and priority.
The HSRP virtual MAC address format is 0000.0C07.AC_____ where the last two digits are the group number in hex.
Answer: xx
HSRP virtual MAC = 0000.0C07.ACxx where xx is the group number in hexadecimal.
End devices must be reconfigured when an HSRP failover occurs.
- True
- False
Answer: False
HSRP failover is transparent to end devices — they keep using the same virtual IP as their default gateway.
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