Learning by Doing: CISCO Certified Network ... - SCN Research

In line 1 we see our Q931 requesting (transmission: TX) a handshake procedure to setup
an ISDN connection with certain parameters. Here the source is asking “can I connect to
you?” Line 2 is the reception of the setup request to allow the “call to proceed.” In
other words, the destination is responding with “I am not busy so you can connect to me.”
Line 3 is our source actually connecting to the destination. Line 4-5 shows us the line
coming up and connected with a number (555-1234). Line 6 is our destination telling the
source “the line is established so you can bring up your interface and start sending
information.” Line 7 shows us the source BRI is brought up and we can now transmit our
data.
Data Link Layer:
Let’s start with our LAP-D negotiation (Q.921). This will negotiate the setting up of our
SPID’s. Again, I used a BRI that was not connected, enabled the debug isdn q921, and
then pinged the other BRI. (Don’t forget to turn off debug from the last step…it would
be too confusing).
kissane#debug isdn q921
ISDN Q921 packets debugging is on
kissane#ping 192.168.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 32/32/32 ms
01:52:21: ISDN BR0/0:TX -> INFOc sapi = 0 tei = 64 ns = 22 nr = 20 i = 0x0
8010805040288901801832C0735353531323334
01:52:90194354176: ISDN BR0/0: RX INFOc sapi = 0 tei = 64 ns = 23 nr = 22 i = 0x0
801080F
01:52:90194313216: ISDN BR0/0: RX