Second B Channel causes connection to drop

[trismegistus]

Hi
We have a 1700 series supplying a DDR link to a server. It transports mainly http and ftp. We use bandwidth on demand to initiate the second channel. The second channel does come up, with no problem actually coming up.

The problem is that the initiation of the second B channel causes all connections through the router to drop. Browser reports page unavailable, ftp server reports dropped connection etc.

I have posted the config below, any ideas would be extremely welcome before I get burned at the stake....

!
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
no service tcp-small-servers
no service udp-small-servers
!
hostname Router
!
enable password xxxxxx
!
no ip name-server
!
isdn switch-type basic-net3
!
ip subnet-zero
no ip domain-lookup
ip routing
!
interface Dialer 1
description connected to Internet
ip address negotiated
ip nat outside
no ip split-horizon
encapsulation ppp
dialer in-band
dialer idle-timeout 120
dialer string xxxxxxxxxxxxxx
dialer hold-queue 10
dialer load-threshold 10
dialer-group 1
ppp authentication chap pap callin
ppp chap hostname leiston
ppp chap password xxxxxxxx
ppp pap sent-username leiston password xxxxxxxxx
ppp multilink
no cdp enable
!
interface FastEthernet 0
no shutdown
description connected to EthernetLAN
ip address xxxxxxxxxxxx 255.255.255.0
ip nat inside
keepalive 10
!
interface BRI 0
no shutdown
description connected to Internet
no ip address
dialer rotary-group 1
!

!

access-list 1 permit xxxxxxxxxxxxx 0.0.0.255
!
!
!
dialer-list 1 protocol ip permit
!
!
ip nat translation timeout 86400
ip nat translation tcp-timeout 86400
ip nat translation udp-timeout 300
ip nat translation dns-timeout 60
ip nat translation finrst-timeout 60
ip nat inside source list 1 interface Dialer 1 overload
!

!
service dhcp
ip dhcp excluded-address xxxxxxxxxxxxxxxxxxxxxxxx
ip dhcp excluded-address xxxxxxxxxxxxxxxxxxxxxxxx
xip dhcp excluded-address xxxxxxxxxxxxxxxxxxxxxxx
ip dhcp pool 1
network xxxxxxxxxxxxxxx 255.255.255.0
domain-name students
default-router xxxxxxxxxxxxxxx
dns-server xxxxxxxxxxxxx xxxxxxxxxxxxxx
!
router rip
version 2
network 192.168.220.0
passive-interface Dialer 1
no auto-summary
!
!
ip classless
!
! IP Static Routes
ip route 0.0.0.0 0.0.0.0 Dialer 1
no ip http server
snmp-server community public RO
no snmp-server location
no snmp-server contact
!
line console 0
exec-timeout 0 0
password xxxxx
login
!
line vty 0 4
password xxxxxx
login
!
memory-size iomem 25
!
end

 

[KiscoKid]

I used to get exactly this issue with certain versions of IOS for the 1700.

Debug would show the 2nd multilink connection kick in but mysteriously wouldn't get added to the existing bundle. The link would drop and connectivity would be lost.

I contacted TAC and they recommended (eventually) I try IOS 12.2(10a) and now it works fine for me.

My config was fairly similar to yours. I would try upgrading your IOS and let us know if it makes a difference.