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4.5.1. FHRP Overview
| Protocol | Standard | Virtual MAC Format | Best For |
|---|---|---|---|
| HSRP | Cisco proprietary | 0000.0c07.acXX | Cisco-only networks |
| VRRP | IETF (RFC 5798) | 0000.5e00.01XX | Multi-vendor environments |
| GLBP | Cisco proprietary | 0007.b400.XXYY | Load balancing (rare) |
XX = HSRP/VRRP group number in hex. GLBP uses a more complex format.
Which one will you see on the exam? HSRP is Cisco's baby and gets the most attention. VRRP operates almost identically but uses different terminology (master/backup vs active/standby). GLBP appears occasionally—it's unique because it can load-balance by giving different clients different virtual MACs. One GLBP router is elected the AVG (Active Virtual Gateway); it answers ARP requests for the single virtual IP with different virtual MACs, each owned by an AVF (Active Virtual Forwarder), so up to four routers forward at once.
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Written byAlvin Varughese
Founder•20 professional certifications