Layer-3 Switching vs. Routing – End the Confusion!
Remember also that, switching functions were typically performed in
hardware, and routing functions were typically performed in software. This
resulted in a widespread perception that switching was fast, and routing was
slow (and expensive).
Once Layer-3 forwarding became available in hardware, marketing gurus
muddied the waters by distancing themselves from the term router. Though
Layer-3 forwarding in hardware is still routing in every technical sense, such
devices were rebranded as Layer-3 switches.
Ignore the marketing noise. A Layer-3 switch is still a router.
Compounding matters further, most devices still currently referred to as
routers can perform Layer-3 forwarding in hardware as well. Thus, both
Layer-3 switches and Layer-3 routers perform nearly identical functions at
the same performance.
There are some differences in implementation between Layer-3 switches and
routers, including (but not limited to):
• Layer-3 switches are optimized for Ethernet, and are predominantly
used for inter-VLAN routing. Layer-3 switches can also provide
Layer-2 functionality for intra-VLAN traffic.
• Switches generally have higher port densities than routers, and are
considerably cheaper per port than routers (for Ethernet, at least).
• Routers support a large number of WAN technologies, while Layer-3
switches generally do not.
• Routers generally support more advanced feature sets.
Layer-3 switches are often deployed as the backbone of LAN or campus
networks. Routers are predominantly used on network perimeters,
connecting to WAN environments.
Multilayer Switching
The evolution of network technologies has led to considerable confusion
over the terms switch and router. Remember the following:
• The traditional definition of a switch is a device that performs Layer-2
forwarding decisions.
• The traditional definition of a router is a device that performs Layer-3
forwarding decisions.
over the terms switch and router. Remember the following:
• The traditional definition of a switch is a device that performs Layer-2
forwarding decisions.
• The traditional definition of a router is a device that performs Layer-3
forwarding decisions.
Remember also that, switching functions were typically performed in
hardware, and routing functions were typically performed in software. This
resulted in a widespread perception that switching was fast, and routing was
slow (and expensive).
Once Layer-3 forwarding became available in hardware, marketing gurus
muddied the waters by distancing themselves from the term router. Though
Layer-3 forwarding in hardware is still routing in every technical sense, such
devices were rebranded as Layer-3 switches.
Ignore the marketing noise. A Layer-3 switch is still a router.
Compounding matters further, most devices still currently referred to as
routers can perform Layer-3 forwarding in hardware as well. Thus, both
Layer-3 switches and Layer-3 routers perform nearly identical functions at
the same performance.
There are some differences in implementation between Layer-3 switches and
routers, including (but not limited to):
• Layer-3 switches are optimized for Ethernet, and are predominantly
used for inter-VLAN routing. Layer-3 switches can also provide
Layer-2 functionality for intra-VLAN traffic.
• Switches generally have higher port densities than routers, and are
considerably cheaper per port than routers (for Ethernet, at least).
• Routers support a large number of WAN technologies, while Layer-3
switches generally do not.
• Routers generally support more advanced feature sets.
Layer-3 switches are often deployed as the backbone of LAN or campus
networks. Routers are predominantly used on network perimeters,
connecting to WAN environments.
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