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New Member

ISDN BRI idle-timeout problem [BRI as a backup interface]

Hello to everybody,

Let me explain the problem:

On a Cisco 2600 router, "Interface Serial1/1" is the primary link to HQ. BRI0/0 is configured as a backup interface of Ser1/1. EIGRP is the dynamic routing protocol in between the brach and HQ. BRI initializes itself in just 10 seconds after Ser1/1 goes down. Upto now, everything seems o.k. However, ISDN link goes down/and gets up immediately within 120 seconds after the BRI interface is comming up. And whole scenerio repeats itself in every 120 sec period.

It is not an expected action indeed. Because dialer idle-timeout equals to 600 sec, and all ip traffic is interesting (please check dialer-list 1). Besides, EIGRP hellos should make the ISDN link up until the primary link goes up again, shouldn't it?

I could not conclude in a meaningful reason for this problem. IOS version of the branch router is 12.1(4) IP Plus feature set [c2600-is-mz.121-4.bin]. I have a doubt on IOS bug.

Relevant config can be seen below. Any help will be useful.

Onur

******************

interface BRI0/0

ip unnumbered Loopback0

encapsulation ppp

dialer idle-timeout 600

dialer string 902123501900

dialer load-threshold 180 either

dialer-group 1

isdn switch-type basic-net3

no cdp enable

ppp authentication chap

ppp multilink

!

!

interface Serial1/1

backup delay 10 15

backup interface BRI0/0

ip unnumbered Loopback0

no ip mroute-cache

no fair-queue

!

!

router eigrp 1200

network 30.0.0.0

no auto-summary

no eigrp log-neighbor-changes

!

dialer-list 1 protocol ip permit

******************

8 REPLIES
New Member

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

I have seen something similar to this before.

If you are dialing from a bri to a pri,I think IP needs to be enabled and enter the BRI interface in the EIGRP 30.0.0.0 network.

Do a show ip EIGRP interfaces to see if the bri interface is in the routing table,it is not going to be because it has not been defined by the EIGRP routing process. This method is not useful if you are dialing into a pri.

I dont think you will be able to route any traffic on layer 3 if the main interface goes down.

Bronze

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

The first question is who is intiating the disconnect (the 2600 or the other end); "debug isdn q931" would confirm that. If it's the 2600, "debug dialer" might indicate why. Regardless, if it is the 2600 it looks like a bug, since as you say all IP is interesting and the idle-timer is 600. Would it be possible to upgrade the 2600 to the latest 12.1 code?

Silver

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

This behavior is consistent with the called router not being configured to recognize that the traffic on the dial link is "interesting." Remember that either end can hang up the call. This would be apparent from a "debug isdn events" at either end which will tell you which end of the link is hanging up the call.

You can also so a "show dialer" at each end and see which end is idling out.

Good luck and good hunting!

VIncent C Jones

www.networkingunlimited.com

New Member

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

ur backup delay command in the int s1/1 has very poor parameters

try giving atleast 20-30 s of difference between the two like

backup delay 10 35

New Member

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

I think that what you said is not related with the problem. Because I have tried ISDN connection without the use of backup interface command, and the same problem occured again.

Here is the config of the router on my side:

!

interface BRI0/0

bandwidth 64

ip address 10.100.125.25 255.255.255.252

ip nat outside

encapsulation ppp

dialer idle-timeout 600

dialer string 902123501900

dialer load-threshold 180 either

dialer-group 1

isdn switch-type basic-net3

no cdp enable

ppp authentication chap

ppp multilink

!

I have changed the IOS of 2600 router to 12.1.(5)T9 IP feature set. However, it still cuts the connection after 120 seconds. Other side is a Dialer interface, and interesting traffic is defined for all IP packets on that Dialer (as "dialer-list 1 protocol ip permit"). Besides, there is not any "dialer idle-timeout" command on the other side.

Instead of 600 seconds, why does it cut the connection after 120 seconds? Problem is still on air..

Onur

Bronze

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

Again, "debug isdn q931" will confirm who is initiating the disconnect. Please try the latest version of 12.1 Mainline, not 12.1T.

New Member

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

You are absolutely right, connection was resumed by the peer side. Here is the log output of my router:

*********************************

Nov 14 19:20:49 Turkey: ISDN BR0/0: RX <- DISCONNECT pd = 8 callref = 0x84

Nov 14 19:20:49 Turkey: Cause i = 0x8190 - Normal call clearing

Nov 14 19:20:49 Turkey: %ISDN-6-DISCONNECT: Interface BRI0/0:1 disconnected from 902123501900 MERKEZ_DISASTER, call lasted 120 seconds

Nov 14 19:20:49 Turkey: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to down

Nov 14 19:20:49 Turkey: ISDN BR0/0: TX -> RELEASE pd = 8 callref = 0x04

Nov 14 19:20:49 Turkey: Cause i = 0x8090 - Normal call clearing

Nov 14 19:20:49 Turkey: ISDN BR0/0: RX <- RELEASE_COMP pd = 8 callref = 0x84

Nov 14 19:20:49 Turkey: Cause i = 0x8190 - Normal call clearing

Nov 14 19:20:50 Turkey: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:1, changed state to down

Nov 14 19:20:50 Turkey: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, changed state to down

*********************************

I will get contact and be checked the configuration of the peer router. Still, I do not know what causes this result on the remote side?

Bronze

Re: ISDN BRI idle-timeout problem [BRI as a backup interface]

Actually, the same advice applies: debug isdn q931at the remote to verify that it is disconnecting (it can be the network that is disconnecting both sides, although unlikely); then review the config to see that it has a dialer-group and dialer-list. Finally, ensure you have most recent 12.1 code, just to be safe.

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