Comprehensive and Detailed Explanation From Exact Extract of HPE Aruba Networking Switching:
On Aruba switches (AOS-CX/AOS-S), multiple IPv4 networks can be configured on the same VLAN interface (SVI) by assigning a primary address and one or more secondary addresses. The VLAN remains one Layer-2 broadcast domain; adding more IP subnets does not create subinterfaces and does not split the broadcast domain.
Exact extract:
“A VLAN interface may be configured with a primary IP address and additional secondary IP addresses to host multiple subnets on the same Layer-2 broadcast domain.”
“A VLAN is a single broadcast domain. Broadcast and unknown unicast frames are flooded to all ports belonging to the VLAN.”
“Hosts in different IP subnets on the same VLAN still require Layer-3 routing to communicate; sharing the VLAN only means they share the same L2 broadcast domain.”
Therefore, when a second subnet is added to the same VLAN, broadcasts (ARP, DHCP, etc.) from devices in either subnet will be flooded to all member ports of that VLAN, making option C correct.
Options A (subinterfaces) are not used here; B is incorrect because inter-subnet traffic still needs routing; D is not categorically true—IGMP operates per VLAN with multicast routing configuration and is not inherently disabled by multiple subnets.
References of HPE Aruba Networking Switching documents or Study Guide:
Aruba AOS-CX Interface and VLAN Configuration Guide — “Primary and secondary IP addressing on VLAN interfaces; VLANs as broadcast domains.”
Aruba AOS-CX Layer 2 Fundamentals — “Flooding behavior for broadcast/unknown frames within a VLAN.”
Aruba Campus Wired Design Fundamentals — “Multiple IP subnets on one VLAN and routing implications.”
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