A water utility edge mixes Cisco and another vendor’s routers and must keep a standards-based first-hop redundancy protocol. Which choice best fits that multi-vendor constraint?
Select an answer to reveal the explanation.
Short Explanation
When the pump house has Cisco on one side and Brand-X on the other, you need a protocol both speak. VRRP is the IETF common language for first-hop HA. HSRP is Cisco’s own dialect—fine in an all-Cisco closet, awkward at a mixed-vendor hydrant.
Full Explanation
A water utility edge that mixes Cisco and another vendor’s routers must keep a standards-based first-hop redundancy protocol. VRRP best fits that multi-vendor constraint because it is the IETF standards-based FHRP suited to mixed-vendor edges sharing a virtual gateway. In a pump-house or treatment-plant edge where Cisco and non-Cisco platforms both terminate access VLANs, VRRP gives a common virtual IP model both vendors implement without locking the design to Cisco-only extensions.
GLBP-only fails because GLBP is Cisco-specific load-balancing FHRP behavior and is not “the sole IETF first-hop standard across all vendors.” HSRP exclusively fails because HSRP is Cisco-proprietary; claiming proprietary Cisco FHRPs always interoperate with every peer is incorrect for a heterogeneous water-utility edge. PIM sparse-mode shared trees fail because multicast RP and shared-tree mechanics are not a default-gateway failover mechanism for first-hop redundancy.
Exam caveat: when the stem stresses multi-vendor or standards-based, prefer VRRP over HSRP/GLBP. When the stem is all-Cisco and emphasizes active/standby virtual gateway, HSRP is often the intended answer. Do not confuse FHRP selection with multicast tree building—PIM answers a different ENCOR domain even if both appear in campus designs.
Operational check: confirm both vendors support the same VRRP version and authentication options, verify virtual IP/MAC ownership with show vrrp (or vendor equivalent) on each peer, and test failover by shutting the master uplink while confirming SCADA and operator endpoints keep the same gateway address.