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Modem DDR question

ciscoguy888
Level 1
Level 1

My company has just upgraded their 1760 router to use a WIC 1T DSU instead of an external CSU/DSU. However, with this new config, I am unable to make the dial backup modem kick in. I've tried manually shutting down the serial interface, pinging to bring up interesting traffic, reloading the router several times, and upgrading the IOS, but I'm still not having any luck. When I go back to my old config of using an external CSU/DSU with the same router, the modem DDR works perfectly fine. Any tips or suggestions? My config is below. Thanks in advance!

version 12.2

service timestamps debug datetime

service timestamps log datetime

service password-encryption

!

hostname test

!

logging queue-limit 100

logging buffered 4096 debugging

enable secret 5

!

username cisco password

username c password

memory-size iomem 25

ip subnet-zero

!

!

no ip domain lookup

ip host c3 192.168.15.45

!

!

chat-script default ABORT ERROR ABORT BUSY ABORT "NO ANSWER" "" "ATDT\T" TIMEOUT 60 CONNECT \c

!

!

!

interface FastEthernet0/0

description connected to EthernetLAN

ip address

ip helper-address

speed auto

!

interface Serial0/0

description

no ip address

encapsulation frame-relay IETF

no ip mroute-cache

no fair-queue

service-module t1 timeslots 1-2

cdp enable

!

interface Serial0/0.1 point-to-point

ip address

frame-relay class LINKWATCH

frame-relay interface-dlci 53

!

interface Serial1/0

physical-layer async

description dial backup line

ip address

encapsulation ppp

dialer in-band

dialer idle-timeout 300

dialer map ip 192.168.45.9 name c modem-script default broadcast 13105551212

dialer hold-queue 10

dialer-group 1

no keepalive

cdp enable

ppp authentication chap

!

interface Serial1/1

no ip address

!

ip classless

ip route 0.0.0.0 0.0.0.0 192.168.45.9 200

no ip http server

!

!

!

!

map-class frame-relay LINKWATCH

frame-relay end-to-end keepalive mode request

dialer-list 1 protocol ip permit

!

snmp-server community public RO

snmp-server packetsize 2048

snmp-server enable traps tty

banner motd ^CCCCCCC

\\\///

/ _ _ \

(| (.)(.) |)

-----------------.OOOo--()--oOOO.--------------------------------

------------------.oooO------------------------------------------

( ) Oooo.

\ ( ( )

\_) ) /

(_/

^C

!

line con 0

exec-timeout 0 0

login local

line 2

flush-at-activation

modem InOut

modem autoconfigure type usr_sportster

transport input all

stopbits 1

speed 57600

flowcontrol hardware

line aux 0

login local

modem InOut

modem autoconfigure type usr_sportster

speed 57600

flowcontrol hardware

line vty 0 4

login local

!

no scheduler allocate

ntp clock-period 17178900

ntp peer 192.168.3.4

end

5 Replies 5

Hello,

can you post the output of:

debug dialer events

debug ppp negotiation

debug ppp authentication

By the way, did this configuration work as is with the external DSU/CSU ? I can see only a default route pointing to the async line, and no default route to anything else. Also, if you place the command:

backup interface serial 1/0

in the Serial0/0.1 config, the backup line automatically kicks in when the main line goes down.

Regards,

Georg

Georg,

The config I used for the external DSU/CSU is practically the same as the one I posted except that there isn't a WIC 1T DSU interface (Serial 0). I used the "backup interface serial1/0" command on the serial0/0.1 interface (as you suggested) but when I bring the main link down, I get a message saying:

Interface serial1/0, changed state to standby mode/disable

The modem doesn't try to dial out. And I don't see any debug outputs. Any other suggestions? Thanks for all your help.

Hello,

just to be sure, how do you bring down the primary line ? I guess you are aware that administratively shutting down the line will not work, this is Cisco-specifc I guess, the backup interface does not consider this a failure. You will need to unplug the cable. If you have done that and it still does not work, can you post the output of the debugs mentioned earlier ?

Regards,

Georg

Georg,

Here's my output when I unplugged the cable to the main link.

*Mar 1 00:50:45: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to down

*Mar 1 00:50:52: Se1/0 DDR: re-enable timeout

g620#

*Mar 1 00:53:22: %LINK-3-UPDOWN: Interface Serial0/0, changed state to down

The modem just won't dial out. I have no problems at all with an external DSU/CSU.

Georg,

Turns out that I didn't have a default route pointing to serial1/0 (backup interface). Thanks for all your help!