2.1 Explain characteristics of routing technologies
📘CompTIA Network+ (N10-009)
First Hop Redundancy Protocol (FHRP)
Definition:
FHRP is a network protocol that provides high availability for the first hop (default gateway) in a network. In simpler terms, it ensures that if the primary router or gateway fails, another router automatically takes over so devices on the network do not lose connectivity.
Think of it as a backup system for network gateways. Devices always need a gateway to reach other networks or the internet. FHRP ensures there’s no single point of failure.
Why FHRP is Important
- Network reliability: Ensures users and devices stay connected even if a router fails.
- Minimizes downtime: Automatic failover happens without manual intervention.
- Critical for large networks: Especially in enterprise IT environments with multiple routers.
Without FHRP, if a gateway router fails, all devices using it would lose connectivity until a network admin manually reconfigures them to use a different router.
How FHRP Works
- Multiple routers are configured to share a virtual IP address.
- The virtual IP acts as the default gateway for devices.
- One router is the active router (handles all traffic initially).
- Other routers are standby routers (wait in case the active router fails).
- If the active router goes down, a standby router automatically takes over the virtual IP and starts routing traffic.
This failover is transparent to devices—they continue sending traffic to the same IP without noticing any change.
Common FHRP Protocols
There are three main FHRP protocols you should know for the Network+ exam:
1. HSRP – Hot Standby Router Protocol
- Cisco proprietary.
- One router is active, another is standby.
- Other routers in the group listen but do not forward traffic.
- Uses a virtual IP and MAC address.
- Failover happens quickly if the active router fails.
2. VRRP – Virtual Router Redundancy Protocol
- Open standard (not vendor-specific).
- Similar to HSRP but allows multiple routers to participate.
- One router is master, others are backup.
- Automatic failover if the master router fails.
- Faster failover than HSRP in some cases.
3. GLBP – Gateway Load Balancing Protocol
- Cisco proprietary.
- Unique feature: Load balancing across multiple routers.
- Each router can simultaneously handle traffic, not just one active.
- Ensures better resource utilization and redundancy.
Key Terms to Remember
- Virtual IP (VIP): IP address that devices use as their default gateway.
- Active/Primary Router: Router currently forwarding traffic.
- Standby/Backup Router: Router waiting to take over if active fails.
- Failover: Automatic switch from one router to another.
- Hello Messages: Periodic messages sent between routers to check each other’s status.
Exam Tips
- Know the purpose of FHRP: provide gateway redundancy.
- Be able to identify differences:
- HSRP → active/standby (Cisco)
- VRRP → master/backup (open standard)
- GLBP → load balancing + redundancy (Cisco)
- Understand virtual IP concept and failover process.
- Remember FHRP increases network uptime, which is critical for enterprise networks.
Summary Table
| Protocol | Vendor | Roles | Key Feature |
|---|---|---|---|
| HSRP | Cisco | Active, Standby | One active, one standby, others listen |
| VRRP | Standard | Master, Backup | Open standard, fast failover |
| GLBP | Cisco | Active, Active/Load sharing | Load balances traffic across multiple routers |
✅ Bottom Line:
FHRP keeps a network running smoothly by making sure there’s always a working gateway. It prevents downtime and makes networks more reliable, especially in IT environments where many devices rely on constant connectivity.
