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Backup Router Query

‎10-14-2010 01:43 AM

Hello community

 

I am trying to understand a certain things about the backup router.

 

As far as my understanding goes if u have router A connected directly to router B in your network then you can configure

 

Router B as backup router to reach certain destinations.

 

What if both router A and B are connected to an ISP for internet reachability then i cant list all the destination reachable at internet through router B .

 

In the case we dont specify the destination a default router will be installed but juniper gives a precaution of not to install a default route in forwarding table.

 

My questions are

 

1- Is there any specific risk when u install a default route in the forwarding table eventhough it is removed from the

     forwarding table once the RPD of router A restarts

 

2-what should be the backup router IP The IP address of the interface directley connected to router A or loopback

 

3- What if i install router A as backup for router B and router B backup for router A

 

Thanks & Regards

 

Malik

3 REPLIES 3
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Junos

Re: Backup Router Query

‎10-14-2010 08:47 AM

Dear Malik,

 

check the below link. i hope it will resolve the issue.

 

http://www.juniper.net/techpubs/en_US/junos9.6/topics/task/configuration/backup-router-configuring.h...

 

Regards

 

Farooq

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Junos

Re: Backup Router Query

[ Edited ]
‎10-23-2010 06:51 AM

Hello Farooq

 

Thank you for the reply.

Actually the link provided doesn't actually satisfies my question .

What more i learned was that backup router only works when there are 2 routing engines Why is it so ??

Secondly the backup router should be the out of band IP of the directly connected router for that you need a static route towards the fxp of your directly connected router.

 

Thirdly backup router is just configured to genrate trap not to forward traffic to backup router is it true. Fourth documentaton confuses me Duh . It some time feels as that you configure backup to access the management of the router whose RPD restarts. Can you please clear these points.

 

Thanks & Regards

Malik

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Junos

Re: Backup Router Query

‎10-25-2010 03:37 PM

The purpose of the backup-router statement is not to forward transit/pfe traffic.  This is for local management of the router, via the out of band interface (fxp0).  It allows the router to install a default or static route to a destination, before the routing protocol process (rpd) is up and running.  My answers to your questions are below.

 


malik1 wrote

 ...

My questions are

 

1- Is there any specific risk when u install a default route in the forwarding table eventhough it is removed from the

     forwarding table once the RPD of router A restarts

 

2-what should be the backup router IP The IP address of the interface directley connected to router A or loopback

 

3- What if i install router A as backup for router B and router B backup for router A

 

Thanks & Regards

 

Malik


 

A1. There shouldn't be any risks assoicated with doing this.  Just make sure the backup router address specified is reachable and directly connected.  When RPD starts, the backup route is removed.  And, any default static, or protocol learned route will be installed.  In the case of a backup routing-engine (usually RE1), the backup router remains active, unless Nonstop Routing is configured.

 

A2. The backup router address should be an address that is directly connected to fxp0.

 

A3. This can work if the fxp0 of each router is connected to aninterface on the other router, that provides the reachability you need.

 

This is probably a good time to point out that traffic is not forwarded between pfe and fxp0 interfaces.

 

 

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