156-816.61 · Question #79
Which of the following VSX components maintain Layer-3 connectivity?
The correct answer is E. Virtual Router. Virtual Router (E) is the only VSX component designed to operate at Layer 3 - it maintains IP routing tables, participates in routing protocols (OSPF, BGP, etc.), and forwards packets between networks based on IP addresses, making it the component responsible for Layer-3…
Question
Which of the following VSX components maintain Layer-3 connectivity?
Options
- AVirtual System in Bridge Mode
- BVLAN interface
- CInternal Virtual Switch
- DExternal Virtual Switch
- EVirtual Router
How the community answered
(48 responses)- B2% (1)
- C4% (2)
- D2% (1)
- E92% (44)
Explanation
Virtual Router (E) is the only VSX component designed to operate at Layer 3 - it maintains IP routing tables, participates in routing protocols (OSPF, BGP, etc.), and forwards packets between networks based on IP addresses, making it the component responsible for Layer-3 connectivity.
Virtual System in Bridge Mode (A) operates at Layer 2 by transparently bridging traffic between interfaces without inspecting or maintaining IP routing state. VLAN interfaces (B) are Layer-2 segmentation constructs; while they can carry tagged frames, they don't independently maintain routing. Internal (C) and External (D) Virtual Switches both function as Layer-2 switching fabrics - the Internal switch connects virtual systems to each other, and the External switch connects them to physical networks, but neither performs IP routing.
Memory tip: The answer is in the name - only a Router routes, and routing is the defining function of Layer 3. When you see "Virtual Router" in a VSX component list, it's the sole owner of the routing table.
Topics
Community Discussion
6
Anjali D.Feb 21, 2026The correct answer is E, Virtual Router. In a VSX environment, the Virtual Router is the component explicitly designed to handle Layer-3 functions, meaning it maintains routing tables, performs IP forwarding, and routes traffic between different network segments or Virtual Systems. The other options all fall short on this front: Virtual Switches, both Internal and External, operate at Layer 2 and just move frames without caring about IP addressing, and a Virtual System in Bridge Mode is similarly a Layer-2 construct that passes traffic transparently without routing it. VLAN interfaces can carry Layer-3 addressing but they are interface-level configurations, not a standalone VSX component that "maintains" L3 connectivity the way the question is asking. Our group spent a while debating whether VLAN interfaces counted here, and the consensus was that the question is asking about a VSX component with a dedicated routing function, which points squarely to the Virtual Router. Has anyone seen a variation of this question that tries to trick you with the Internal Virtual Switch? Would love to hear how others reasoned through the distractors.
Dejan C.Feb 23, 2026The VLAN interface distractor is the sneaky one because sk98348 and the VSX admin guide both confirm that a VS in Router Mode is what owns the routing table, and a Virtual Router is really just a dedicated VS instance stripped down to pure L3, so the distinction holds but it is worth knowing they share the same kernel routing stack under the hood.
Samuel O.Feb 27, 2026The Virtual Router is the right call here, and if you have any routing background this one should feel familiar because it behaves almost exactly like a dedicated router VRF sitting inside the VSX chassis, complete with its own routing table and forwarding logic. The trap option for me was B, the VLAN interface, because in real life a VLAN interface with an IP address absolutely does Layer-3 work, and you will configure them constantly in VSX deployments, but the exam is asking about the VSX component category, not the interface type bolted onto a component. The Virtual Switches, internal or external, are Layer-2 constructs that shuttle frames around without caring about IP, and a Virtual System running in Bridge Mode is doing exactly what the name says, which is transparent bridging at Layer 2. So when the question asks what maintains Layer-3 connectivity as its core function within the VSX architecture, the Virtual Router is the only answer that holds a routing table, participates in routing protocols, and makes hop-by-hop forwarding decisions the way you would expect a router to.
Lena V.Feb 6, 2026The Virtual Router is the right call here. It is the VSX component that handles Layer-3 routing between Virtual Systems, maintaining IP connectivity and routing tables just like a physical router would.
Grace U.Feb 14, 2026Went with B first, then remembered only the Virtual Router actually routes.
Dejan C.Mar 5, 2026E, though B tempts you since VLANs carry IP, the Virtual Router owns routing tables.