Note the Frame-Relay encapsulation commands in Table 11.6.
When configuring Frame Relay on Cisco routers, you need to specify it as an encapsulation
on serial interfaces. As I said earlier, you can’t use HDLC or PPP with Frame Relay. When you
configure Frame Relay, you specify an encapsulation of Frame Relay (as shown in the following
output). But unlike HDLC or PPP, with Frame Relay there are two encapsulation types:
Cisco and Internet Engineering Task Force (IETF). The following router output shows these
two different encapsulation methods when Frame Relay is chosen on your Cisco router:
RouterA(config)#int s0
RouterA(config-if)#encapsulation frame-relay ?
ietf Use RFC1490 encapsulation
TABLE 1 1 . 6 Frame-Relay Encapsulation Commands
Command Meaning
interface interface Chooses your interface
encapsulation frame-relay Sets the Frame Relay encapsulation to Cisco
encapsulation frame-relay ietf Sets the Frame Relay encapsulation to IETF
The default encapsulation is Cisco unless you manually type in ietf, and Cisco is the type
to use when connecting two Cisco devices. You’d opt for the IETF-type encapsulation if you
needed to connect a Cisco device to a non-Cisco device with Frame Relay. Whichever you
choose, make sure the Frame Relay encapsulation is the same on both ends.