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isdn loop question??


when I use isdn to my backup line on router,and finish to setup isdn configuration,and try to connect isdn,I find can't connect isdn,and I find this messege below..

BRI0/0 is up, line protocol is up (spoofing)

BRI0/0:1 is up, line protocol is down (looped)

my question is why bri0/0:1 will show looped,is the ISP problem or my isdn conf is wrong?

here is my isdn config

interface BRI0/0

description ISDN NO:04-8111-193

bandwidth 128

ip unnumbered Loopback0

ip access-group 109 out

no ip directed-broadcast

encapsulation ppp

no ip mroute-cache

dialer idle-timeout 180

dialer string 0422109152

dialer string 0422109138

dialer string 0281711953

dialer string 0281711942

dialer load-threshold 160 either

dialer-group 1

isdn switch-type basic-net3

ppp authentication chap

ppp multilink


you have used "dialer load-threshold 160 either " command which means that second B channel will be triggered only when inbound or outbound load on first B channel is more than approx 63%, due to which I feel you are observing second B channel as looped.

you said that you are configuring ISDn as backup. what is the primary link config? can you post config of your router?


here is my serial interface conf

interface Serial0/0

bandwidth 512

backup interface BRI0/0

ip address

no ip directed-broadcast

encapsulation ppp

no ip mroute-cache

priority-group 1

traffic-shape group 103 144000 148000 152000 1000

traffic-shape group 102 128000 132000 136000 1000

traffic-shape group 101 224000 228000 232000 1000

could you post the output from the commands 'show isdn status' and 'show int bri0/0'? Looped could be a telco issue.

can you share complete output of show interface bri0/0, show interface bri0/0:1 and show isdn status?

if primary link goes down, is traffic shifting to backup link or not?


here is bri 0/0:1 and isdn status


BRI0/0:1 is administratively down, line protocol is down

Hardware is PQUICC BRI

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 Closed, multilink Closed


Last input 01:12:50, output 01:12:50, output hang never

Last clearing of "show interface" counters 16:31:45

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

1654 packets input, 37327 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

1654 packets output, 37327 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

151 carrier transitions


isdn status

Global ISDN Switchtype = basic-net3

ISDN BRI0/0 interface

dsl 0, interface ISDN Switchtype = basic-net3

Layer 1 Status:


Layer 2 Status:

Layer 2 NOT Activated

Layer 3 Status:

0 Active Layer 3 Call(s)

Activated dsl 0 CCBs = 0

The Free Channel Mask: 0x80000003

Number of L2 Discards = 30, L2D_Task Discards = 29

please attend to it is none isdn dialup status.

BRI0/0:1 is administratively down. You need to do "no shut" the interface. once done check the interface status and see if it works.

if not, please paste the output of interface and isdn status again.

hope it helps ...


From the output which you have pasted i feel your ISDN interface is shut make sure that your giving no shut command under the main physical bri interface to make it up..