Problem with automatic ISDN BRI U Backup Interface

[jmarin]

I have a cisco 1700 router running 12.1(3) that has one Serial interface for a point-to-point T1, and one BRI U interface for a backup ISDN BRI if the serial interface goes down. Here's my running config:

Current configuration:

!

version 12.1

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

!

hostname sub-aquatics

!

enable secret xxx

enable password ******

!

username irim-max6k-alpha password 0 ******

!

!

!

!

memory-size iomem 25

ip subnet-zero

ip name-server 69.x.64.8

ip name-server 69.x.64.9

!

isdn switch-type basic-ni

!

!

!

interface Serial0

description Jade Inc.

backup delay 30 60

backup interface BRI0

ip address 69.46.x.x.255.255.252

encapsulation ppp

load-interval 30

no fair-queue

service-module t1 timeslots 1-24

!

interface BRI0

description Backup to Jade

ip address 69.x.x.x.255.255.252

encapsulation ppp

dialer idle-timeout 2000000

dialer string 5527100

dialer load-threshold 1 either

dialer-group 1

isdn switch-type basic-ni

isdn spid1 xxxx

isdn spid2 xxxx

isdn send-alerting

isdn sending-complete

no cdp enable

ppp authentication chap pap callin

ppp chap hostname SubAquatics

ppp chap password xxxx

ppp pap sent-username xxx password xxx

ppp multilink

!

interface FastEthernet0

ip address 69.x.x.x.255.255.192

load-interval 30

speed auto

!

ip classless

ip route 0.0.0.0 0.0.0.0 Serial0

ip route 0.0.0.0 0.0.0.0 BRI0 200

no ip http server

!

snmp-server engineID local xxxx

snmp-server community public RO

!

line con 0

transport input none

line aux 0

line vty 0 4

password ******

login

!

no scheduler allocate

end

I pulled this config from another 1700 which is performing this fine, but for some reason when I shutdown the serial interface, or unplug the T1 from it to bring it down, the BRI is not Activating and trying to dial. It just sits there. Can anyone tell me if there's something wrong with my config? Am I missing a command to tell the backup interface to start dialing once the serial is down?

Any help will be appreciated!

[tyoung008]

Can you give me more details on what you mentioned as the best practice?

Certainly!

For your configuration, I would use this command, "dialer map ip 69.x.x.x name irim-max6k-alpha broadcast 5527100" instead of the dialer string command. It is the traditional way to configure BRI. It creates a static dialer map, where the dialer string is dynamic. I have occasionally seen problems with the dialer string command on the BRI interface. For the command, the IP address would be of the remote router. The "name" keyword is needed because you are using CHAP authentication. The "broadcast" keyword is only needed if you want to send broadcast or multicast traffic over the circuit (e.g., routing protocol).

Thanks,

Tom

[b-watkins]

Whoever told you that the BRI will show as Layer 1 DEACTIVATED when it's in backup mode is wrong. Here is the result of a show isdn status on one of my routers that is configured almost exactly like yours:

ISDN BRI0/0 interface

dsl 0, interface ISDN Switchtype = basic-ni

Layer 1 Status:

ACTIVE

Layer 2 Status:

TEI = 122, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

I_Queue_Len 0, UI_Queue_Len 0

TEI = 123, Ces = 2, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

I_Queue_Len 0, UI_Queue_Len 0

Spid Status:

TEI 122, ces = 1, state = 5(init)

spid1 configured, spid1 sent, spid1 valid

Endpoint ID Info: epsf = 0, usid = 70, tid = B

TEI 123, ces = 2, state = 5(init)

spid2 configured, spid2 sent, spid2 valid

Endpoint ID Info: epsf = 0, usid = 71, tid = B

Layer 3 Status:

0 Active Layer 3 Call(s)

Activated dsl 0 CCBs = 0

Total Allocated ISDN CCBs = 0

As you can see, all looks well. In fact, the BRI interface is actually up/up but the bearer channels are not. This is what you should see.

[jmarin]

I just wanted to let everyone know that I was able to get this working once I upgraded to 12.2. I had to make some other small config changes, so I'm not sure whether it was those changes or the upgrade that fixed my problem, or even if it was just adding in the dialer-list command, but everything is up and running now. Thanks again