Discussions are a very strong key to gain information, yesterday during a discussion with some of my friends about Frame-Relay -Thanks to everyone of them- and the reasons that could make a Frame-Relay connection to become down everyone agreed that LMI mismatch and wrong Mapping are the main known reasons, Then the below question has been raised “Is Frame-Relay encapsulation mismatch could be a reason?” – the answer is definitely NO, but Why? we are here to answer this question 🙂
There are two types of Frame-Relay encapsulations, IETF “Global Standard” and Cisco. Sure Cisco devices can encapsulate packets using any of the two standards and other vendors like “Juniper, HP, Huawei,etc…” can only use the global standard IETF and to answer the mentioned question we firstly have to know how it works.
Frame-Relay encapsulation is end-to-end between DTE “FR client routers“, in short the configured way of encapsulation means how to encapsulate the OUTGOING packets only not the way of Decapsulating the incoming packets, applying this logic if both ends are Cisco devices you can configure one end to encapsulate the outgoing packets using Cisco standard while the other end uses IETF. Sure without mentioning that if both devices don’t belong to the same vendor you have to configure them to use IETF encapsulation as at least one end won’t understand Cisco encapsulation.
|NETSCOUTS2#show run int ser 1/0
Building configuration…Current configuration : 146 bytes
ip address 10.10.10.2 255.255.255.0
serial restart-delay 0
frame-relay interface-dlci 75
endNETSCOUTS2#show int ser 1/0 | i Encaps
Encapsulation FRAME-RELAY, crc 16, loopback not set
NETSCOUTS2#ping 10.10.10.1Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/48/80 ms
|NETSCOUTS1#show run int ser 1/0
Building configuration…Current configuration : 151 bytes
ip address 10.10.10.1 255.255.255.0
encapsulation frame-relay IETF
serial restart-delay 0
frame-relay interface-dlci 50
NETSCOUTS1#show int ser 1/0 | i Encaps
Encapsulation FRAME-RELAY IETF, crc 16, loopback not set
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.2, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/38/52 ms