ISDN problem

Unanswered Question
Feb 12th, 2007


Can any one help me , i m facing one problem , im using ISDN line & leased line .Everything going smooth when using leased line (All aplication and VOIP phone working properly.)but when i switch over to ISDN line (For backup purpose) connectivity very slow and VOIP phone not working properly. Is that due to routing table problem?

Plz help me


I have this problem too.
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spremkumar Mon, 02/12/2007 - 21:50

Hi Manoj

do revert back how you want to have your traffic routed ..

If you are going to use the GRE tunnel for forwarding the traffic to your remote location then make sure that your default route pointing towards the tunnel 0.

To reach the tunnel destination via serial and bri create static routes one with admin distance via BRI the other one without any admin distance via serial.

If you still have ips to be routed then point them via serial with a backup route pointing thme via bri.

ip route Tunnel10

ip route Serial 0/0

ip route BRI1/0 100


smothuku Mon, 02/12/2007 - 21:51

Hi ,

In config file I observed that you have give same subent to leased line and isdn line.


interface Serial0/0

description *****LL to xx 2MB ******

bandwidth 128

ip address


interface BRI1/0

ip address

encapsulation ppp

Configure different subent for bri1/0 and chec the issue.



spremkumar Mon, 02/12/2007 - 22:25

Hi Satish

Since hes using backup interface command under serial interface having the same ip address wont have any effect on the routing table.

The bri interface will be considered shut till the serial is up once the serial goes down then only the bri interface will be activated.

I have seen this kinda config in working environments also better to have the same ip on both serial and bri to have single end to end tunnel created between the peers.

Also if we want to have ipsec vpn then this kinda config comes handy...



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