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Backup link bouncing up and down

Unanswered Question
Nov 28th, 2013
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Hello,

we have primary MPLS link and backup ISDN on our Cisco 1921 routers, i have noticed that logs show ISDN link keeps going up, and then down after a couple of seconds. I dont see any reason for this happening since our primary link seems to be working fine. Any ideas? Im pasting relevant information below, thank you for reading.


....

Nov 27 13:32:49: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 86 changed to down

Nov 27 13:36:28: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 87 changed to up

Nov 27 13:36:43: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 87 changed to down

Nov 27 13:39:06: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 88 changed to up

Nov 27 13:39:21: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 88 changed to down

Nov 27 13:46:16: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 89 changed to up

Nov 27 13:46:31: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 89 changed to down

Nov 27 13:56:13: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 90 changed to up

Nov 27 13:56:28: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 90 changed to down

Nov 27 13:59:40: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 91 changed to up

Nov 27 13:59:55: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 91 changed to down

Nov 27 14:07:51: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 92 changed to up

...


????#sh isdn status

Global ISDN Switchtype = basic-net3

ISDN BRI0/0/0 interface

        dsl 0, interface ISDN Switchtype = basic-net3

    Layer 1 Status:

        ACTIVE

    Layer 2 Status:

        TEI = 72, Ces = 1, SAPI = 0, State = TEI_ASSIGNED

    Layer 3 Status:

        0 Active Layer 3 Call(s)

    Active dsl 0 CCBs = 0

    The Free Channel Mask:  0x80000003

    Total Allocated ISDN CCBs = 0



.....





interface BRI0/0/0

no ip address

encapsulation ppp

dialer pool-member 1

isdn switch-type basic-net3

isdn point-to-point-setup

ppp authentication chap

no cdp enable

!

interface Dialer1

bandwidth 64

ip address **** 255.255.255.0

ip flow ingress

encapsulation ppp

no ip route-cache cef

no ip route-cache

ip summary-address eigrp **** 255.255.252.0

dialer pool 1

dialer order round-robin

dialer string 03*******

dialer string 03*******

dialer string 03*******

dialer string 03*******

dialer string 03*******

dialer hold-queue 40

dialer load-threshold 220 outbound

dialer-group 1

ppp authentication chap

ppp multilink

fair-queue

no cdp enable

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Richard Burts Thu, 11/28/2013 - 06:36
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I would suggest running the debug for ISDN Q931. Perhaps also the debug dialer. These should show whether it is something from your side bring up the interface or whether it is responding to something from outside.


HTH


Rick

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