Configuring DDR Pots as a backup to an ISDN connection

[Mark_Matthias]

I am attempting to back up an ISDN link with a floating static DDR POTS line route.

and am using the example in Document ID: 10214 {Configuring ISDN Backup for WAN Links Using Floating Static Routes} as a reference assuming most concepts will be similar.

In the example, there is an information line stating "bandwidth is adjusted for rapid backup of this link'.

I would assume I need to do this to my primary link (the ISDN BRI port). What bandwidth should I use? Something less than 56 or 128?

FYI: I am using RIP and not EIGRP. The document indicates this does not matter.

Also, in the same example, it is indicated that the administrative distance for the primary (Frame-relay) route is 90 {" EIGRP learnt route will be installed in the routing table because of its lower administrative distance 90"}. Where can I find out what the default administrative weights are? What would the weight be of my primary link ISDN, in a RIP situation?

Here's a link to the example I am referencing:

http://www.cisco.com/en/US/tech/tk713/tk237/technologies_configuration_example09186a00800a3b77.shtml

Thanks

Mark Matthias

[Richard Burts]

Mark

The default administrative distance for RIP is 120. This link leads to a pretty good article which describes the functionality of administrative distance and has a nice chart summarizing the various administrative distances:

http://www.cisco.com/en/US/partner/tech/tk365/technologies_tech_note09186a0080094195.shtml

I have looked at the link that you referenced. It adjusts bandwidth because EIGRP uses bandwidth for several of its calculations. If you are using RIP instead of EIGRP then I see no reason to manipulate the bandwidth, since RIP does not calculate anything with bandwidth.

And their example has the access list for interesting traffic deny EIGRP as interesting which you should change to make RIP not interesting. Note that denying the routing protocol in the access list does not mean that the routing protocol can not be transmitted over the ISDN link. It only means that it can not bring the link up (or keep it up).

As a side note: I notice in the link that you reference that they set the administrative distance of the floating static route to 200. That is a fairly safe value, but it does happen to equal the administrative distance for IBRP routes (which may or may not matter depending on the particular environment of your network). I prefer to use a value greater than 200 for floating static routes so that there is no possibility of a dynamic routing protocol entry with administrative distance equal or greater than the floating static.

HTH

Rick

HTH

Rick