First Hop Redundancy Protocols (HSRP, VRRP, GLBP), the gateway redundancy mechanisms that keep clients connected when a router fails. Articles tagged FHRP cover the three protocols compared, configuration patterns, STP integration, and Cisco IOS XE walkthroughs.
Dual-active HSRP is invisible from one router: each end looks like a healthy Active gateway until you put both outputs side by side and see Standby=unknown on each. Captured live on IOS XE 17.18.2 in CML, plus the preempt behavior that silently inverts your design.
A working HSRP config is two lines per router, but priority, preemption, tracking, and timers decide how it behaves in production. Walk the full setup on Cisco IOS XE, from the virtual IP to the four settings people skip.
All 6 HSRP states (Initial, Learn, Listen, Speak, Standby, Active), what drives the election, why preempt matters, interface tracking, and real show standby output.
Most FHRP comparisons are a table and nothing else. This one runs HSRP, VRRP and GLBP at the same time on the same two routers, so you can read Active/Standby against MASTER/BACKUP against AVG/AVF, decode each protocol's virtual MAC, and watch GLBP keep both routers forwarding for one virtual...
GLBP (Gateway Load Balancing Protocol) is Cisco's load-balancing FHRP. AVG, AVFs, three load balancing methods, configuration, and when GLBP is actually the right answer.
VRRP (Virtual Router Redundancy Protocol, RFC 5798) is the vendor-neutral FHRP. How it works, master election, IP address owner trap, vs HSRP, Cisco IOS XE configuration, and tracking.
A complete HSRP deployment with object tracking on IOS XE, broken on purpose: the track falls, priority drops 110 to 90, the standby preempts, and the host never notices. All output captured live.