Switch – Cabling standard for Layer-3 switch

cablecisco-catalystlayer1layer3switch

I want to know the appropriate cable type between:

  1. Layer-2 and Layer-3 switch
  2. Layer-3 switch and router

Is it cross-over or straight through?

Best Answer

I want to know the appropriate cable type between:

  1. Layer-2 and Layer-3 switch
  2. Layer-3 switch and router

Is it cross-over or straight through?

You need to make the distinction between MDI ports and MDI-X ports.

  1. Standard cable connects MDI to MDI-X.
  2. Crossover cable connects either MDI to MDI or MDI-X to MDI-X.

Traditionally both Layer-2 and Layer-3 switches use MDI-X ports, while routers and servers use MDI ports. But one ought to check.

See detailed explanation below, from: https://en.wikipedia.org/wiki/Medium-dependent_interface

With 10BASE-T and 100BASE-TX separate twisted pairs are used for the two directions of communication. Since twisted pair cables are conventionally wired pin to pin there are two different pinouts used for the medium dependent interface. These are referred to as MDI and MDI-X (medium dependent interface crossover). When connecting an MDI port to an MDI-X port a straight through cable is used while to connect two MDI ports or two MDI-X ports a crossover cable must be used. Conventionally MDI is used on end devices while MDI-X is used on hubs and switches. Some network hubs or switches have an MDI port (often switchable) to connect to other hubs or switches without a crossover cable.

Also, modern network ports often support Auto MDI-X:

Auto MDI-X automatically detects the required cable connection type and configures the connection appropriately, removing the need for crossover cables to interconnect switches or connecting PCs peer-to-peer.

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