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Community Member

ISDN Huge bill

I replaced the router with a 1750 router with ISDN as backup (T1 primary) I forgot to put backup delay command under serial int (as shown below) the isdn kept connecting/disconnecting within seconds and we got like $23k for isdn bill I am wondering if it was just due to that one line or why will it keep connecting again.. Please help

interface Serial0/0.1 point-to-point

bandwidth 1536

( backup delay 45 60)

backup interface Dialer1

ip address x.y.x.y 255.255.255.248

ip access-group 199 in

no ip redirects

ip nat outside

ip inspect AM-firewall out

no ip mroute-cache

ntp disable

no cdp enable

frame-relay interface-dlci 500 IETF

crypto map AM-region

----------------------------------------------------------

interface Dialer1

description connected to AM

ip unnumbered Ethernet0/0

encapsulation ppp

no ip route-cache cef

no ip split-horizon

dialer in-band

dialer idle-timeout 60

dialer string 12141112222 class 2JerichoBRI

dialer string 12141112222 class 2JerichoBRI

dialer string 12141112222 class 2JerichoBRI

dialer string 12141112222 class 2JerichoBRI

dialer string 12141112222 class 2JerichoBRI

dialer string 12141112222 class 2JerichoBRI

dialer hold-queue 10

dialer load-threshold 2 either

dialer-group 1

no cdp enable

ppp authentication chap

---------------------------------------------------------------------------

Apr 27 13:50:20.900: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 12141112222 N/A

Apr 27 13:50:21.396: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down

Apr 27 13:50:25.548: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up

Apr 27 13:50:25.548: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 12141112222 N/A

Apr 27 13:50:26.048: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down

Apr 27 13:50:30.348: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up

Apr 27 13:50:30.348: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 12141112222 N/A

Apr 27 13:50:30.848: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down

Apr 27 13:50:34.848: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up

5 REPLIES
Hall of Fame Super Silver

Re: ISDN Huge bill

Hello ManjinderPal,

what is the interesting traffic definition

dialer-list 1 ?

I see you have no ip split horizon if you use RIP you need to deny RIP as interesting traffic or it will keep up the link.

However, this quick up/downs look like not ruled by DDR because your idle timeout is 60 seconds it should stay up for 60 seconds after a successful call.

I would use

debug isdn q921

debug isdn q931

debug dialer

to see why these calls are started and why are terminated so quickly

Hope to help

Giuseppe

Community Member

Re: ISDN Huge bill

The dialer list is

dialer-list 1 protocol ip permit

Actually I even the backup interface command was not there.

The quick up/downs really surprises me (split second).. I am running Eigrp through GRE tunnel..

I can't run debug because the line is disconnected.. Any clue

Thanks

Blue

Re: ISDN Huge bill

Hi:

Giuseppe is right.

You have to figure out which traffic is bringing the dialer interface up. This traffic is known as "interesting traffic." You want to make sure that you create an ACL for your dialer-list that will deny the kind of traffic that the router will broadcast or multicast out all interfaces, like eigrp traffic.

You can take 2 approaches, either permit exactly what you want and let the implicit deny handle the rest. Or you can specifically deny the traffic you know will bring up the interface and permit everything else.

You need to turn on debugging, configure ip accounting, use a sniffer, etc, to examine the ISDN traffic.

By the way, I used to troubleshoot such problems after receiving an incredibly high bill all the time. It can be fun, playing detective. :-)

Good luck.

Victor

Community Member

Re: ISDN Huge bill

but why was it dialing every split second??

Blue

Re: ISDN Huge bill

TURN DEBUGGING ON TO FIND OUT.

Excuse the CAPS, but the recommendation has been made 3 times, so I am wondering if youre seeing it or not. :-)

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