System information

Troubleshooting ATM Switching Environments
Book Title
21-446
ATM Switching: Virtual Circuit Fails to Be Created
Symptom: A Frame Relay, frame forwarding, UNI, or constant bit rate (CBR) virtual circuit fails to
be created.
Table 21-6 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 21-6 ATM Switching: Virtual Circuit Fails to Be Created
Possible Problem Solution
LMI
1
type mismatch
1 LMI = Local Management Interface
Step 1
Use the show port port-number all command to see whether the
Normal Packets Received counter is incrementing. A packet should
be received every 10 seconds from the Frame Relay host.
Step 2 If the counter is not incrementing, check the Discarded Received
Packets statistic. If the Discarded Received Packets entry is
incrementing, the packets are coming in but on a different DLCI
2
.
This occurs when there is an LMI type mismatch.
Step 3 Make sure that both the Frame Relay port and the Frame Relay host
are configured to use the same LMI protocol (FRIF, ANSI T1 617D,
or Q933A). Use the show port c.p framerelay command to check
the LightStream 2020 port. For information on checking and
configuring the LMI type on the Frame Relay host, refer to the
vendor documentation.
Step 4 Change the LMI type on the port using the set port c.p framerelay
lmiconfig {none | frif | ansi_t1_617d | q933a} command and see
whether the port becomes active. If the LMI does not come up, make
sure that packets are being received on the LMI DLCI. The FRIF
LMI uses DLCI 1023. The ANSI and Q933A LMIs use DLCI 0.
2 DLCI = Data Link Connection Identifier
Port protocol incorrect Step 1 Use the show port c.p framerelay command to make sure that the
LightStream 2020 port is correctly configured as a UNI
3
port or an
NNI
4
port.
In general, ports should be configured to use the UNI protocol. The
NNI protocol is designed for network device–to–network device
connection and is rarely used.
Step 2 If the port protocol is incorrect, use the set port port-number
framerelay netinterfacetype {nni | uni} command to reconfigure
it.
3 UNI = User-Network Interface
4 NNI = Network-to-Network Interface
DLCI is not activated Step 1 Use the show port c.p listdlci command to see whether the Frame
Relay DLCI is deactivated. The output will show an uppercase I in
front of the DLCI entry if it has been manually deactivated.
Step 2 If the DLCI is deactivated, use the set port port-number dlci
dlci-number activate command to activate the DLCI.