A network engineer is designing a campus network with high availability for critical services. Which Cisco technology enables traffic to be forwarded to an alternate next hop in the event of a first-hop router failure, without requiring any configuration changes on the hosts?
Trap 1: Static default route with a floating static
A static default route with a floating static is a router-level failover mechanism, not a first-hop redundancy protocol. It relies on a higher administrative distance for a backup route, but hosts are still configured with a single default gateway IP address. If the active router fails, that gateway IP becomes unreachable until the host is manually reconfigured or a dynamic protocol like ICMP redirects takes over, so it is not transparent to hosts. Additionally, floating static routes cannot provide sub-second failover because they depend on recursive routing table changes.
Trap 2: GLBP
GLBP (Gateway Load Balancing Protocol) does provide first-hop redundancy and automatic failover, but its primary feature is load balancing across multiple routers that all forward traffic for the same virtual IP. While GLBP uses an active virtual gateway (AVG) to assign virtual MAC addresses to hosts, it introduces more operational complexity than HSRP for simple failover scenarios. In a campus network where the design goal is high availability without the need for load sharing, HSRP is traditionally preferred because it offers a straightforward active/standby model with deterministic behavior, making GLBP less appropriate for this specific requirement.
Trap 3: VRRP
VRRP (Virtual Router Redundancy Protocol) is an open standard FHRP that functions very similarly to HSRP by sharing a virtual IP and MAC between multiple routers. However, VRRP is not Cisco proprietary, and in a campus network built entirely with Cisco equipment, HSRP is the native, best-integrated choice. Additionally, VRRP's failover behavior is based on priority and the master router's hello advertisements, but it lacks some of the Cisco-specific enhancements like the ability to track interface states with the same granularity as HSRP. Since the question likely expects a Cisco-centric answer, VRRP, while technically valid, is not the intended solution.
- A
Static default route with a floating static
Why it fails: A static default route with a floating static is a router-level failover mechanism, not a first-hop redundancy protocol. It relies on a higher administrative distance for a backup route, but hosts are still configured with a single default gateway IP address. If the active router fails, that gateway IP becomes unreachable until the host is manually reconfigured or a dynamic protocol like ICMP redirects takes over, so it is not transparent to hosts. Additionally, floating static routes cannot provide sub-second failover because they depend on recursive routing table changes.
- B
GLBP
Why it fails: GLBP (Gateway Load Balancing Protocol) does provide first-hop redundancy and automatic failover, but its primary feature is load balancing across multiple routers that all forward traffic for the same virtual IP. While GLBP uses an active virtual gateway (AVG) to assign virtual MAC addresses to hosts, it introduces more operational complexity than HSRP for simple failover scenarios. In a campus network where the design goal is high availability without the need for load sharing, HSRP is traditionally preferred because it offers a straightforward active/standby model with deterministic behavior, making GLBP less appropriate for this specific requirement.
- C
VRRP
Why it fails: VRRP (Virtual Router Redundancy Protocol) is an open standard FHRP that functions very similarly to HSRP by sharing a virtual IP and MAC between multiple routers. However, VRRP is not Cisco proprietary, and in a campus network built entirely with Cisco equipment, HSRP is the native, best-integrated choice. Additionally, VRRP's failover behavior is based on priority and the master router's hello advertisements, but it lacks some of the Cisco-specific enhancements like the ability to track interface states with the same granularity as HSRP. Since the question likely expects a Cisco-centric answer, VRRP, while technically valid, is not the intended solution.
- D
HSRP
HSRP (Hot Standby Router Protocol) is a Cisco-proprietary FHRP that provides transparent gateway failover by presenting a virtual IP and virtual MAC address to hosts. The active router answers ARP requests for the virtual IP and forwards traffic, while the standby router monitors the active router via hello messages and takes over if the active router fails. Hosts always use the same virtual IP as their default gateway, so they experience zero interruption to the default gateway address and require no configuration changes during a failover. HSRP also supports object tracking and timers that enable sub-second failover, making it the standard choice for simple redundant gateway designs in Cisco campus networks.