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back up link for fast ethernet

Unanswered Question
May 2nd, 2006
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hi,

the scenario is like this that i have two 1841 routers, one is at the branch end an the other is at the central office, each having the bri wic, both the routers are connected through DSL modem on fast ethernet ports, the problem is that i want to setup a redundant link for backup puropse using the bri 1/0 on the both the routers, ppp is not running on the fastethernet. the question is how will the router tell the bri to initiate an isdn call in case of the failure of the fast ethernet link? Also, how how will the call to the destination be actually placed? Please reply with configurations if possible.

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ankurbhasin Tue, 05/02/2006 - 02:47
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Hi Friend,


I think we can play around with flotating static route.


Configure 2 static routes one for fast ethernet interface and another pointing to bri interface with higher admin distance.


Something like this


ip route 0.0.0.0 0.0.0.0

ip route 0.0.0.0 0.0.0.0 250


If the fast ethernet interface goes down the default static route with higher admin dist will be preferred.


Regards,


Ankur

waqasashraf1 Tue, 05/02/2006 - 03:05
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/Can this also be done with the dial watch if i use dial watch conf do i have to use PPPoE (ppp on ethernet)or will the normal ppp do the trick. can you provide me a sample conf for the dial watch, if possible. also, thanks for the prompt reply and helps alot, one thing that incase of the failure of the ethernet will the other route be choosen automatically and also do i need to configure the bri interface as backup interface ? (b/c i dont think we donot need to do that)

spremkumar Tue, 05/02/2006 - 02:58
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Hi


You need to have a mechanism in place to detect the link failures with ethernet interfaces.


Etherenet interface will remain up/up though your link is off or down so to really detect the failures and establish the back up connectivity you can make use of Object Tracking feature available in cisco IOS.


This feature can help in detecting the link failures between locations with the tracking feature configured on the routers..


http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html


if you are using simple dialers instead for both DSL and BRI then you can simply define 2 routes one thru the dialer created over DSL and the backup route thru the dialer created over the bri interface.


regds


waqasashraf1 Tue, 05/02/2006 - 03:41
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can you please elaborate the following statement

if you are using simple dialers instead for both DSL and BRI then you can simply define 2 routes one thru the dialer created over DSL and the backup route thru the dialer created over the bri interface


how can this be done? should i use the normal backup technique (dialers and etc)? or are there modifications to it ? again how will the backup interfce BRI know if the fast ethernet port has gone down? Is EOT neccessary to implement this or is there any way around it? i wish to use DDR, is it possible.

spremkumar Tue, 05/02/2006 - 04:18
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Hi


In this case you have one more option left which is again creating a simple GRE tunnel over the primary and secondary and route the traffic with normal static routes as i hve mentioned in my previous post.

That will also help you to get the redundant links available for the remote destination.


I mentioned to have 2 routes assuming that your primary dialer interface built over DSL goes off/down when theres no connectivity..


regds


waqasashraf1 Tue, 05/02/2006 - 05:50
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thanks for the help, can you tell me how to set up a dialer interface over a fast ethernet. dsl is connected to the fast ethernet. secondly can the floating static routes be used? MY biggest concern is that how will the bri interface know if the primary link through dsl(fast ethernet) has gone down (b/c ethernet stays up/up) and then dial the remote sites string? b/c bri will be nactive and t needs to be activated(dial) when it is chosen as the best route to the remote site? Is EOT the only solution for this?

spremkumar Tue, 05/02/2006 - 21:08
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hi


Can you post out the current config you have in place ? so that suitable suggestions can be given ..


regds


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