1841 router isdn interface up but fail to dial.

[jacksonc]

Hi,

Recently we have purchased some 1841 routers with Serial and ISDN modules. The 1841 is to replace the 1760 router (out of sales) due to our network expansion.

We noticed the ISDN interface Bri0/1/0 and BRI0/1/0:1 interface is up but did not dial. Only when the ISDN cable is unplug and plug back then it starts to dial and connect successfully to our core router.

I have tested the 1760 with 123-14.T7 ISO code, no problem at all. The ISDN is able to dial automatic with out unplugging and reconnect back.

Below are the results of the test and the Serial/ISDN configuration. Please advice.

1. Using 1760 router with c1700-y-mz.123-14.T7.bin

No problem encounter, everything working as per normal. Able to ping to core router after ISDN connection kicks up (ping test perform to the core router).

2 Using 1841 router with c1841-ipbase-mz.124-1c.bin (default IOS come with router)

Pull out the serial cable by simulate serial connection fail. We noticed the ISDN * BRI0/1/0 is up but not BRI0/1/0:1

3. Using 1841 router with c1841-entbase-mz.123-14.T7.bin.

Pull out the serial cable by simulate serial connection fail. We noticed the ISDN interface BRI0/1/0 and BRI0/1/0:1 is up but dialing intermittent. 1st time unplugged the serial, it will auto dial and connect successful. But fail on second time onwards.

4. Using 1841 router with c1841-entbase-mz.124-8c.bin

Pull out the serial cable by simulate serial connection fail. We noticed the ISDN interface BRI0/1/0 and BRI0/1/0:1 is up but fail to dial. Only when the ISDN cable is unplug and plug then it starts to dial and connect successfully to our core router (ping test perform to the core router)

!

interface Serial0/0/0

bandwidth 64

backup delay 30 30

backup interface BRI0/1/0

backup load 80 30

ip address XX.X.XXX.XXX 255.255.XXX.XXX

ip access-group 110 in

no fair-queue

no cdp enable

!

interface BRI0/1/0

ip address XX.X.XXX.XXX 255.255.XXX.XXX

ip access-group 110 in

encapsulation ppp

dialer idle-timeout 300

dialer string 65529092

dialer-group 1

isdn switch-type basic-net3

isdn point-to-point-setup

ppp authentication chap

!

ip route XX.X.XXX.XXX 255.255.0.0 Serial0/0/0

ip route XX.X.XXX XXX 255.255.0.0 BRI0/1/0

!

Best regards,

Jackson

[paolo bevilacqua]

Hi,

there may be bug in ISDN driver. Can you upgrade to latest 12.4 and check again ?

Also try configuring "isdn tei-negotiation preserve".

Hope this helps, please rate post if it does!

[jacksonc]

Hi,

Where to add the "isdn tei-negotiation preserve"? Under the Bri0/1/0 statement? Please advice (Will try)

I thought of isdn bug also but the TAC Support told me that they have no problem on their end (they did test on their lab).

Th Tac support suspect it may be the isdn module faulty and a replacement is on the way.

According to my experience and testing, it may be the router and the ISO version problem because our existing routers are 1700 series and ISO version are YXX-12.3.

Sudden change from 1800 series and 124 maybe to big jump. I am worry the existing NT box (ISDN moden) maybe not compatiable with new 1800 router and ISO.

Best regards,

Jackson

[paolo bevilacqua]

yes like all isdn command, "tei-negotiation" is configured under interface.

Please collect output of "debug isdn q921" and "debug isdn q931" when attempting a call.

[spremkumar]

Hi Jackson

Can you remove backup interface/load command under the serial interface and modify the static route pointing towards bri 0/1/0 with some admin distance attached to it either 10 or 20 ?

Once you are done with the same try to swich off the csu/dsu device and check whether the fall back is happenining or not..

regds