Saturday, 23 February 2013

WAN Support

Basically, Cisco just supports HDLC, PPP, and Frame Relay on its serial interfaces, and you can see this with the encapsulation? command from any serial interface (your output may vary depending on the IOS version you are running):

Corp# config t
Corp(config)# int s0/0/0
Corp(config-if)# encapsulation ?
atm-dxi           ATM-DXI encapsulation
frame-relay     Frame Relay networks
hdlc                 Serial HDLC synchronous
lapb                 LAPB (X.25 Level 2)
ppp                  Point-to-Point protocol
smds               Switched Megabit Data Service (SMDS)
x25                  X.25

Understand that if I had other types of interfaces on my router, I would have other encapsulation options, like ISDN or ADSL. And remember, you can’t configure Ethernet or Token Ring encapsulation on a serial interface.

Next, I’m going to define the most prominently known WAN protocols used today: Frame Relay, ISDN, LAPB, LAPD, HDLC, PPP, PPPoE, Cable, DSL, MPLS, and ATM. Just so you know, the only WAN protocols you’ll usually find configured on a serial interface are HDLC, PPP, and Frame Relay, but who said we’re stuck with using only serial interfaces for wide area connections?

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