View Dial Backup Status

Problem

You want to check on the dialer status of a router.

Solution

Here are some useful commands for looking at the status of a dial backup link. For dial backup that uses the floating static or dialer watch type configurations, you can use the show dialer command:

Router1#show dialer

For dial configurations that use the backup interface configuration, you can use the show backup command:

Router1#show backup

And, for backup configurations that use ISDN, you can get some additional information from the show isdn status, show isdn active, and show isdn history commands:

Router1#show isdn status
Router1#show isdn active
Router1#show isdn history

 

Discussion

The show dialer command provides a lot of useful information about existing dial sessions, as well as some historical statistics:

Router1#show dialer
BRI0 - dialer type = ISDN

Dial String Successes Failures Last DNIS Last status
0 incoming call(s) have been screened.
0 incoming call(s) rejected for callback.

BRI0:1 - dialer type = ISDN
Idle timer (300 secs), Fast idle timer (20 secs)
Wait for carrier (30 secs), Re-enable (15 secs)
Dialer state is data link layer up
Dial reason: ip (s=10.1.99.55, d=224.0.0.10)
Interface bound to profile Dialer1
Current call connected 00:03:18
Connected to 95551212 (dialhost)

BRI0:2 - dialer type = ISDN
Idle timer (120 secs), Fast idle timer (20 secs)
Wait for carrier (30 secs), Re-enable (15 secs)
Dialer state is idle

Dialer1 - dialer type = DIALER PROFILE
Load threshold for dialing additional calls is 100
Idle timer (300 secs), Fast idle timer (20 secs)
Wait for carrier (30 secs), Re-enable (15 secs)
Dialer state is data link layer up
Number of active calls = 1
Number of active circuit switched calls = 0

Dial String Successes Failures Last DNIS Last status
95551212 2 0 00:03:19 successful Default
Router1#

There is a lot of useful information in this output. First, notice that there is an active dial session on the first B channel of this ISDN BRI interface, BRI0:1. It has been connected for a little more than three minutes, and you can see the dial string that represents the remote telephone number. The second ISDN B channel, BRI0:2, is not connected, presumably because the router has yet not seen the minimum traffic threshold that we specified for bringing up the second channel, or perhaps it isn't configure for PPP multilink.

But there is another extremely important piece of information here. Notice the line marked "Dial reason." This shows the source and destination IP addresses of the packet that originally caused the router to start the dial session. In this case, the source IP address is 10.1.99.55, which is the IP address of the dial interface itself. The destination IP address is 224.0.0.10, which is extremely interesting because this is the multicast IP address that EIGRP uses to talk between routers. This is fine if we intended for this dial connection to remain up all the time. However, if this router was supposed to only dial when a primary link failed, then looking at this output should tell you that the dialer list configuration is wrong.

The bottom of the display includes some historical information about each of the configured dial strings, and how often the router has been able to connect successfully using each string. In this case, there is only one dial string, but if there were several, they would all appear with their respective totals.

The show backup command is only useful when you use the backup interface configuration, which is discussed in Recipe 13.4:

Router1#show backup

 
Primary Interface Secondary Interface Status
----------------- ------------------- ------
Serial0/0 BRI0/0 active backup

In this case, the interface BRI0/0 is actively operating as a backup for the primary interface, Serial0/0, because it has become unavailable. If the primary interface is working properly, the Status column will say "normal operation." In this case, the backup interface will go into a standby mode:

Router1#show interface bri0/0
BRI0 is standby mode, line protocol is down 
 Hardware is BRI
 Internet address is 10.1.99.55/24
 MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, 
 reliability 255/255, txload 1/255, rxload 1/255
 Encapsulation PPP, loopback not set
 Last input never, output never, output hang never
 Last clearing of "show interface" counters never
 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
 Queueing strategy: weighted fair
 Output queue: 0/1000/64/0 (size/max total/threshold/drops) 
 Conversations 0/0/16 (active/max active/max total)
 Reserved Conversations 0/0 (allocated/max allocated)
 Available Bandwidth 48 kilobits/sec
 5 minute input rate 0 bits/sec, 0 packets/sec
 5 minute output rate 0 bits/sec, 0 packets/sec
 0 packets input, 0 bytes, 0 no buffer
 Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
 0 packets output, 0 bytes, 0 underruns
 0 output errors, 0 collisions, 7 interface resets
 0 output buffer failures, 0 output buffers swapped out
 0 carrier transitions
Router1#

If you are using ISDN for dial backup in any of the configurations discussed, you can get other useful information through the various show isdn commands:

Router1#show isdn status
Global ISDN Switchtype = basic-ni
ISDN BRI0/0 interface
 dsl 0, interface ISDN Switchtype = basic-ni
 Layer 1 Status:
 ACTIVE
 Layer 2 Status:
 TEI = 89, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
 TEI = 90, Ces = 2, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
 TEI 89, ces = 1, state = 8(established)
 spid1 configured, spid1 sent, spid1 valid
 Endpoint ID Info: epsf = 0, usid = 70, tid = 1
 TEI 90, ces = 2, state = 8(established)
 spid2 configured, spid2 sent, spid2 valid
 Endpoint ID Info: epsf = 0, usid = 71, tid = 2
 Layer 3 Status:
 1 Active Layer 3 Call(s)
 Activated dsl 0 CCBs = 1
 CCB:callid=801A, sapi=0, ces=1, B-chan=1, calltype=DATA
 The Free Channel Mask: 0x80000002
Total Allocated ISDN CCBs = 2
Router1#

This example shows a single active call on one of the ISDN B channels. The lines that say that each SPID was configured, sent, and considered "valid" by the switch are also useful. In this case, we were connected to a basic-ni type switch, which requires us to manually configure SPIDs. It is important to check that the switch accepted these values.

If there are active calls, then the output of show isdn active can also be useful:

Router1#show isdn active
--------------------------------------------------------------------------------
 ISDN ACTIVE CALLS
--------------------------------------------------------------------------------
History table has a maximum of 100 entries.
History table data is retained for a maximum of 15 Minutes.
--------------------------------------------------------------------------------
Call Calling Called Remote Seconds Seconds Seconds Charges
Type Number Number Name Used Left Idle Units/Currency
--------------------------------------------------------------------------------
Out [phone] dialhost 207 0 0 
--------------------------------------------------------------------------------

Router1#

Here you can see that there is a single active call. This output also tells you exactly how long the call has been connected, and whether it was an in- or outbound connection. You can also get some potentially useful historical information about previous calls from the show isdn history command:

Router1#show isdn history
--------------------------------------------------------------------------------
 ISDN CALL HISTORY
--------------------------------------------------------------------------------
History table has a maximum of 100 entries.
History table data is retained for a maximum of 15 Minutes.
--------------------------------------------------------------------------------
Call Calling Called Remote Seconds Seconds Seconds Charges
Type Number Number Name Used Left Idle Units/Currency
--------------------------------------------------------------------------------
Out Failed 
Out [phone] dialhost 20 0 
Out [phone] dialhost 219 0 0 
--------------------------------------------------------------------------------

Router1#

This router has attempted to make three outbound calls. The first call failed, the second lasted 20 seconds before disconnecting, and the third lasted 219 seconds. This command can be particularly useful if you think your router might be dialing too often, or that it might be frequently dialing and dropping calls. You can also look in the router's logging buffer for log messages. By default, every time the router dials, it generates at least one log message. Please refer to Chapter 18 for more information on logging.

See Also

Recipe 13.4; Chapter 18