Let's start by connecting our terminal to RouterA. Type the show isdn status command. This command enables you to view the operational status of the BRI circuit that is terminated on the router. The command's output displays layers 1, 2, and 3 ISDN status. We see from the following screen print that layer 1 is active on this circuit. This means that the router senses the 2B1Q line coding of the BRI circuit. Layer 2 status indicates that a TEI has been assigned for both B channels. We also see that the SPIDs for both B channels have been sent to the switch and are valid.
RouterA#show isdn status
The current ISDN Switchtype = basic−ni1 ISDN BRI0/0 interface
Layer 1 Status:
ACTIVE
Layer 2 Status:
TEI = 64, State = MULTIPLE_FRAME_ESTABLISHED TEI = 65, State = MULTIPLE_FRAME_ESTABLISHED Spid Status:
TEI 64, ces = 1, state = 8(established) spid1 configured, spid1 sent, spid1 valid Endpoint ID Info: epsf = 0, usid = 70, tid = 1 TEI 65, ces = 2, state = 8(established)
spid2 configured, spid2 sent, spid2 valid Endpoint ID Info: epsf = 0, usid = 70, tid = 2 Layer 3 Status:
0 Active Layer 3 Call(s) Activated dsl 0 CCBs = 0 Total Allocated ISDN CCBs = 0
Type the show interface bri 0/0 command. We see that the interface is in an up/up(spoofing) state. This means that the D channel is active on the BRI circuit. The D channel is said to be spoofing because it is a local control circuit between the router and the ISDN switch.
RouterA#show interface bri 0/0
BRI0/0 is up, line protocol is up (spoofing) Hardware is QUICC BRI with U interface Internet address is 196.1.1.1/24
MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set
. .
On this ISDN BRI circuit, the actual BRI interface is referenced as bri 0/0. As we saw above, this refers to the D channel of the ISDN circuit. The status of each of the two B channels can also be displayed. This is
accomplished by using the show interface bri 0/0:1 and the show interface bri 0/0:2 commands for channels B1 and B2, respectively. We see that both of these interfaces are in the down/down state. This is because there are no active calls on the BRI circuit at this time.
RouterA#show interface bri 0/0:1
BRI0/0:1 is down, line protocol is down Hardware is QUICC BRI with U interface .
.
RouterA#show interface bri 0/0:2
BRI0/0:2 is down, line protocol is down Hardware is QUICC BRI with U interface .
.
The show dialer command displays the dial and timer status of each B channel that is defined on the router.
We see that there have been 0 attempted calls to 8995201 since the router was last booted. We also see that each B channel will drop its call after 90 seconds of inactivity.
RouterA#show dialer
BRI0/0 − dialer type = ISDN
Dial String Successes Failures Last called Last status 8995201 0 0 never − 0 incoming call(s) have been screened.
BRI0/0:1 − dialer type = ISDN
Idle timer (90 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re−enable (15 secs) Dialer state is idle
BRI0/0:2 − dialer type = ISDN
Idle timer (90 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re−enable (15 secs) Dialer state is idle
The show ppp multilink command will display any active MLPPP bundles on the router. Since there are no active calls, we see that there are no active bundles at this time.
RouterA#show ppp multi No active bundles
Now let's connect to RouterB. The BRI circuit on RouterB is also configured and active as indicated by the show isdn status command shown below.
RouterB#show isdn status
The current ISDN Switchtype = basic−ni1 ISDN BRI0/0 interface
Layer 1 Status:
ACTIVE
Layer 2 Status:
TEI = 64, State = MULTIPLE_FRAME_ESTABLISHED TEI = 65, State = MULTIPLE_FRAME_ESTABLISHED Spid Status:
TEI 64, ces = 1, state = 8(established) spid1 configured, spid1 sent, spid1 valid Endpoint ID Info: epsf = 0, usid = 70, tid = 1 TEI 65, ces = 2, state = 8(established)
spid2 configured, spid2 sent, spid2 valid Endpoint ID Info: epsf = 0, usid = 70, tid = 2 Layer 3 Status:
0 Active Layer 3 Call(s) Activated dsl 0 CCBs = 0 Number of active calls = 0
Number of available B−channels = 2 Total Allocated ISDN CCBs = 0
The show dialer command shows that RouterB will drop a B channel after 90 seconds of inactivity.
RouterB#show dialer
BRI0/0 − dialer type = ISDN
Dial String Successes Failures Last called Last status 0 incoming call(s) have been screened.
BRI0/0:1 − dialer type = ISDN
Idle timer (90 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re−enable (15 secs) Dialer state is idle
BRI0/0:2 − dialer type = ISDN
Idle timer (90 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re−enable (15 secs) Dialer state is idle
The BRI interface status for RouterB is identical to the status of the BRI interfaces that we just examined on Router A. The bri 0/0 interface refers to the D channel of the circuit. This is shown to be in an up/up(spoofing state), indicating that the D channel is active.
RouterB#show interface bri 0/0
BRI0/0 is up, line protocol is up (spoofing) Hardware is QUICC BRI with U interface Internet address is 196.1.1.2/24
MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set
. .
Now let's reconnect to RouterA. Try to ping the ISDN interface of RouterB at IP address 196.1.1.2. Notice that this ping causes RouterA to place two calls to RouterB.
RouterA#ping 196.1.1.2
Type escape sequence to abort.
Sending 5, 100−byte ICMP Echos to 196.1.1.2, timeout is 2 seconds:
%LINK−3−UPDOWN: Interface BRI0/0:1, changed state to up
← Call #1
%LINK−3−UPDOWN: Interface Virtual−Access1, changed state to up
%LINEPROTO−5−UPDOWN: Line protocol on Interface BRI0/0:1, changed state to up
%LINEPROTO−5−UPDOWN: Line protocol on Interface Virtual−Access1, changed state to up
%LINK−3−UPDOWN: Interface BRI0/0:2, changed state to up
← Call #2
%LINEPROTO−5−UPDOWN: Line protocol on Interface BRI0/0:2, changed state to up
%ISDN−6−CONNECT: Interface BRI0/0:2 is now connected to 8995201 RouterB
The ping will be partially successful because some of the ping packets will be sent when the call is being made.
..!!!
Success rate is 60 percent (3/5), round−trip min/avg/max = 20/21/24 ms
After the call has connected, another ping should be 100 percent successful.
RouterA#ping 196.1.1.2
Type escape sequence to abort.
Sending 5, 100−byte ICMP Echos to 196.1.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round−trip min/avg/max = 20/22/24 ms
The show dialer command will now indicate that two successful calls have been made. We see that interface bri 0/0:1 and interface bri 0/0:2 are both online. The dial reason for the call occurring on BRI channel B1 is shown as being traffic from 196.1.1.1 to 196.1.1.2. This was our ping to 196.1.1.2. The dial reason for BRI channel B2 was multilink bundle overload. This overload is determined by the dialer load−threshold command in the router's configuration. The time until each B channel is disconnected is also displayed. Any interesting traffic will reset these numbers to the idle timer.
RouterA#show dialer
BRI0/0 − dialer type = ISDN
Dial String Successes Failures Last called Last status 8995201 2 0 00:00:10 successful 0 incoming call(s) have been screened.
BRI0/0:1 − dialer type = ISDN
Idle timer (90 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re−enable (15 secs) Dialer state is physical layer up
Dial reason: ip (s=196.1.1.1, d=196.1.1.2) ← Reason for dialing was our ping Time until disconnect 76 secs ← Disconnect time
Current call connected 00:00:11 Connected to 8995201 (RouterB)
BRI0/0:2 − dialer type = ISDN
Idle timer (90 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re−enable (15 secs) Dialer state is physical layer up
Dial reason: Multilink bundle overloaded Time until disconnect 77 secs
Current call connected 00:00:12 Connected to 8995201 (RouterB)
Issuing the show ppp multilink command will now show that we have an MLPPP bundle consisting of two members. The two members are bri 0/0:1 and bri 0/0:2.
RouterA#show ppp multi
Bundle RouterB, 2 members, Master link is Virtual−Access1 Dialer Interface is BRI0/0
0 lost fragments, 0 reordered, 0 unassigned, sequence 0x24/0x26 rcvd/sent 0 discarded, 0 lost received, 1/255 load
Member Links: 2
BRI0/0:1 ← These two interfaces make up the MLPPP bundle BRI0/0:2
The D channel of the BRI, shown as bri 0/0, will still indicate that it is in a spoofing state.
RouterA#show interface bri 0/0
BRI0/0 is up, line protocol is up (spoofing) Hardware is QUICC BRI with U interface Internet address is 196.1.1.1/24
MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set
. .
Each of the B channels on the BRI will now be in an up/up state. Notice that both of these B channels have negotiated the multilink protocol with the far−end router.
RouterA#show interface bri 0/0:1 BRI0/0:1 is up, line protocol is up Hardware is QUICC BRI with U interface
MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec)
LCP Open, multilink Open ← MLPPP
Last input 00:00:02, output 00:00:02, output hang never Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec 1191 packets input, 67466 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 1198 packets output, 69418 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets 0 output buffer failures, 0 output buffers swapped out 6 carrier transitions
RouterA#show interface bri 0/0:2 BRI0/0:2 is up, line protocol is up Hardware is QUICC BRI with U interface
MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec)
LCP Open, multilink Open ← MLPPP .
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The show ppp multi, show isdn status, and show interface bri commands on RouterB will display similar output with respect to what we just examined on RouterA.
After the idle timeout period (90 seconds without interesting traffic), the call will disconnect. The following screen print shows the call being brought down and both B channels on the BRI (bri 0/0:1 and bri 0/0:2) being changed to a down state.
%LINEPROTO−5−UPDOWN: Line protocol on Interface Virtual−Access1, changed state to down
%LINK−3−UPDOWN: Interface Virtual−Access 1, changed state to down
%ISDN−6−DISCONNECT: Interface BRI0/0:1 disconnected from 8995201 RouterB, call lasted 99 seconds
%ISDN−6−DISCONNECT: Interface BRI0/0:2 disconnected from 8995201 RouterB, call lasted 96 seconds
%LINK−3−UPDOWN: Interface BRI0/0:1, changed state to down
%LINK−3−UPDOWN: Interface BRI0/0:2, changed state to down
%LINEPROTO−5−UPDOWN: Line protocol on Interface BRI0/0:1, changed state to down
%LINEPROTO−5−UPDOWN: Line protocol on Interface BRI0/0:2, changed state to down