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Cisco Routers

Routing with Cisco 1720 Router for Multi-Service

Basic Troubleshooting Guide

After the router configuration is complete, check the status of the ISDN line by issuing the show isdn status command:

Router1#show isdn status
The current ISDN Switchtype = basic-ni1
ISDN BRI0 interface
  Layer 1 Status:
     ACTIVE
  Layer 2 Status:
    TEI = 70, State = MULTIPLE_FRAME_ESTABLISHED
    TEI = 71, State = MULTIPLE_FRAME_ESTABLISHED
  Layer 3 Status:
    No Active Layer 3 Call(s)
  Activated dsl 0 CCBs = 0
  Total Allocated ISDN CCBs = 0

If layer 1 is not showing ACTIVE, check all cabling from the router to the ISDN jack. Make sure the NT1 has no error lights. Failure to bring up layer 1 means that the router is not detecting a physical link. This could be the result of:

A bad cable
An out-of-service ISDN line
A malfunctioning NT1
A bad BRI interface on the router

If layer 1 is ACTIVE, check Layer 2 status to see if the unit is synchronized with the telco ISDN switch. If you do not see an established frame (as shown above) for each B-Channel, check to see that the SPID numbers and switch type in the router config are in the exact format provided by your telco. You may have to contact your telco to re-verify these parameters.

Layer 3 shows any established connections. If layers 1 and 2 have proper status, you are now ready to establish a connection. From the router, issue a ping to force a call:

Router1#ping 38.9.211.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 38.9.211.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Router1#

The first set of pings will most likely timeout while the router is establishing a connection. The router will signal when the BRI interface is connected:

%LINK-3-UPDOWN: Interface BRI0: B-Channel 1, changed state to up..
%ISDN-6-CONNECT: Interface BRI0: B-Channel 1 is now connected to 2707020
%LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0: B-Channel 1, changed state to up..

Following the established call and authentication, you should have successful pings:

Router1#ping 38.9.211.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 38.9.211.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/188/712 ms
Router1#

If the connection fails and you are still unable to ping out, check all PPP settings. Make sure the login ID and password are entered correctly in your router configuration (BOTH ARE CASE SENSITIVE). Turn on PPP debugging and try to ping out again. Look for errors in the debug output:

Router1#clear counters
Router1#debug ppp negotiation
PPP protocol negotiation debugging is on
Router1#ping 38.9.211.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 38.9.211.2, timeout is 2 seconds:

If there are no errors, yet the pings still fail, try connecting at 56k instead of 64k:

Router1#config t
Enter configuration commands, one per line. End with CNTL/Z.
Router1(config)#no dialer map ip 38.1.1.1 speed 64 name <ACCT ID> < phone #>
Router1(config)#dialer map ip 38.1.1.1 speed 56 name <ACCT ID> < phone #>
Router1(config)#^Z
Router1#wr mem

If pings still fail, contact Technical Support for further assistance.

Cisco 1720: Advanced Troubleshooting

Installation of WIC Interfaces

All Cisco routers will be shipped with the appropriate WIC interfaces installed. The WIC interfaces will be installed in the appropriate slots. Special care must be taken when the WIC interfaces must be changed. Changes may occur if a customer changes from one service to another.

The configuration of the Cisco 1720 is based on the WIC card configuration (i.e. which slots they are inserted in). If the cards are moved around, some configuration lines may be lost upon startup. You will certainly want to save the configuration before changing the WIC interfaces. However, it is best to change the WIC and then erase the startup configuration and reboot. This will ensure that the configuration will match the WIC interface hardware configuration. You may then use the saved configuration to help recover connectivity.

Troubleshooting Serial WIC Interfaces

The physical parameters of the serial interfaces are configured differently than those of a typical Cisco router used for PSINet services. The physical attributes do not display when using the show interface command. The following command can be used to view the detailed physical configuration of the WIC T1 and WIC 56K interface:

show service-module serial [SERIAL INSTANCE]

The WIC T1 DSU can provide a payload loop back. A loop back button is receded on the visible side of the WIC T1 card. Using a pen or a small screw driver press the button once. A LED labeled LP will illuminate orange when the loop back is enabled. To disable the loop back press the loop back button again.

The integrity of the serial WIC interfaces can be tested using the following command:

test service-module serial

The debug command can be used with the serial WIC interfaces:

debug service-module

ISDN WIC Interface

The troubleshooting commands used for the WIC UBRI interface are the similar to those used with any Cisco shipped with PSINet services. A bug was found in the 12.0(7)T IOS.

The command show isdn status resulted in the following:

Global ISDN Switchtype = basic-ni
ISDN BRI0 interface
dsl 0, interface ISDN Switchtype = basic-ni
Layer 1 Status:
ACTIVE
Layer 2 Status:
TEI = 88, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
TEI = 97, Ces = 2, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
TEI 88, ces = 1, state = 8(established)
spid1 configured, spid1 sent, spid1 NOT valid
TEI 97, ces = 2, state = 8(established)
spid2 configured, spid2 sent, spid2 NOT valid
Layer 3 Status:
2 Active Layer 3 Call(s)
Activated dsl 0 CCBs = 2
CCB:callid=8004, sapi=0, ces=1, B-chan=1, calltype=DATA
CCB:callid=8005, sapi=0, ces=2, B-chan=2, calltype=DATA
The Free Channel Mask: 0x80000000
Total Allocated ISDN CCBs = 2

Notice the lines that seem to indicate an invalid SPID (in bold). These lines appear even though there is a connection established using the ISDN interface. This is important to remember when troubleshooting a dial-up connection.