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Community Member

ISDN BRI interface & Gigabit interface failover

Hi All,

I have Cisco 3845 with MPLS on its Gig0/1 interface and ISDN on its BRI 0/2/0 interface is configured.

I am unable to configure its backup failover between the two interfaces means, if MPLS link goes down,BRI should be UP and when it comes UP again, BRI must be Down.

I am using BGP on MPLS link and OSPF over ISDN BRI interfaces.

Further, when this router reboots, till the BGP routes comes up, BRI is connected till the period automatically. How can I stop this problem?

Please suggest / sample configuration..


Anil K.


ISDN BRI interface & Gigabit interface failover

Suggestion would to use OSPF demand on Circuit. Below is a link to read.

Remember, OSPF keeps sending hellos every 10 seconds and freshes the LSA database in 30 mins which may cause your ISDN to fire up abruptly making you pay more $$'s unncessarily.

Hope this helps.



Community Member

ISDN BRI interface & Gigabit interface failover

Hi Vivek,

No, the router is same.

I am facing two issues, first , I want to configure Bri 0/2/0 as a backup of Gig 0/1 ( this is MPLS link) and secondly, whenever this router reboots, instead gig0/1 , Bri0/2/0 will become UP and ISDN call is connected till the BGP routes are learned.

Below is sample config:

interface BRI0/2/0
description ISDN NO:**********
no ip address
encapsulation ppp
dialer rotary-group 1
dialer-group 1
isdn switch-type basic-net3
isdn point-to-point-setup
crypto map XXXXX
interface Dialer1
bandwidth 128
ip address 10.X.X.38
encapsulation ppp
ip ospf network point-to-multipoint
dialer in-band
dialer enable-timeout 320
dialer string 0***********
dialer load-threshold 150 either
dialer watch-group 1
dialer-group 1
ppp multilink
crypto map XXXXX

dialer watch-list 1 ip 10.X.X.X
dialer watch-list 1 delay route-check initial 320
dialer watch-list 1 delay connect 320
dialer watch-list 1 delay disconnect 50
dialer-list 1 protocol ip list 120

Re: ISDN BRI interface & Gigabit interface failover

Ofcourse ISDN interface will be up till the time BGP routes are learnt. I believe once the BGP routes are in, you would have your traffic route via MPLS automatically? Configuration looks Ok to me.

Re: ISDN BRI interface & Gigabit interface failover

Dailer watch-list is kind of a backup itself. If you were to loose the route for your 10.x.x.x (which you learnt via BGP) then your ISDN interface would trigger on the condition that you have a valid "10.x.x.x" route from a different path. Make sure the subnet mask you defined under the dialer watch list is correct & is learnt the same way what you defined.

I hope the ACL 120 has a deny statement to mark OSPF as uninteresting traffic.

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