Frame Relay encapsulation

wpharaon · ‎02-18-2007

Hello experts,

Playing around with Frame Relay, I noticed that setting an end to IETF encapsulation, while other end configured to CISCO encapsulation, won't do any harm: s

2691#sh frame- map

Serial1/0 (up): ip 172.16.0.1 dlci 301(0x12D,0x48D0), static,

broadcast,

CISCO, status defined, active

7206#sh frame-rel map

Serial3/0.101 (up): ip 172.16.0.1 dlci 102(0x66,0x1860), static,

IETF, status defined, active

Serial3/0.101 (up): ip 172.16.0.2 dlci 102(0x66,0x1860), static,

broadcast,

IETF, status defined, active

Serial3/0.101 (up): ip 172.16.0.3 dlci 103(0x67,0x1870), static,

broadcast,

IETF, status defined, active

7206#ping 172.16.0.3

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.0.3, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 116/148/188 ms

7206 can ping 2691, and vice versa is correct

Any explanation for this?

wpharaon · ‎02-19-2007

After some debugging of Frame Relay packets, I found what exactly is going around.

Simply Cisco Routers understands both encapsulations whatever we configure; So setting encapsulation only influence outgoing packets not how to analyse incoming packets, (incoming type is irrelevant for Cisco routers).

Both configured to Cisco encapsulation:

04:14:12: Serial3/0(i): dlci 103(0x1871), pkt type 0x800, datagramsize 104

04:14:12: Serial3/0.101(o): dlci 103(0x1871), pkt type 0x800(IP), datagramsize 104

Local set to IETF encapsulation (outgoing packets), other end to Cisco, So local will receive Cisco encapsulated packets and sends packets using IETF encapsulation "NLPID"

04:15:11: Serial3/0(i): dlci 103(0x1871), NLPID 0x3CC(IP), datagramsize 104

04:15:11: Serial3/0.101(o): dlci 103(0x1871), pkt type 0x800(IP), datagramsize 104

On receiving router:

Serial1/0(i): dlci 301(0x48D1), pkt type 0x800, datagramsize 104

Serial1/0(o): dlci 301(0x48D1), NLPID 0x3CC(IP), datagramsize 104

gokula_chandran · ‎02-19-2007

To add to these i agree that Cisco Routers understands both encapsulations whatever we configure;setting encapsulation only influence outgoing packets if its a non cisco device.

It depends on the remote device response, if its cisco it holds the same encapsulation otherwise it will take IETF.