The Everything Feed - All Packet Pushers Pods N4N041: Switched Virtual Interface (SVI) and Integrated Routing and Bridging (IRB)
Oct 23, 2025
Dive into the fascinating world of networking as the hosts unpack the differences between Switched Virtual Interfaces (SVI) and Integrated Routing and Bridging (IRB). Discover the history of layer 2 and layer 3 communication, along with the challenges that led to these innovative solutions. Learn about the implications of the router-on-a-stick concept and how packet flow operates between VLANs. They also explore the evolution of layer-3 switches, bridging concepts to modern technologies like VXLAN, and the importance of identifying recurring patterns in networking.
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SVI And IRB Are Functionally Equivalent
- SVIs (Cisco) and IRBs (Juniper) are essentially the same concept: a virtual interface tied to a VLAN for routing.
- Vendors use different names, but functionally they serve the same role in modern switches.
Router-On-A-Stick Explains The Need
- Before SVIs, networks used a router (often 'router-on-a-stick') to route between VLANs, causing inefficiency.
- VLAN tagging carried multiple networks over one link and required sub-interfaces on the router.
Catalyst 6500's Dual-Brain Story
- Ethan recounts Catalyst 6500 history where switching and routing lived in separate OSes and later merged into one brain.
- That migration is where SVIs appeared for many engineers as unified layer 2/3 functionality.
