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Routes to dialer interfaces

I am probably supposed to know this already, but I shall swallow my pride and ask anyway:

Suppose I have an ISDN primary rate interface with 30 channels, which provides a dialer pool. I then have several dialer profile interfaces that use that pool. I then make a static route to one of those dialer interfaces, say ip route 192.168.42.0 255.255.255.0 Dialer 6. So far so good ... pretty standard stuff.

I then want to redistribute that static route into, say, OSPF. But I want to arrange it so that if there are no channels in the dialer pool, for example if the ISDN primary rate connection is down, then the route is not redistributed, or even better if it disappears from the access router altogether?

What I am saying is: how can I arrange for a dialer interface to be effectively down whenever the physical interfaces in its dialer pool are down?

N.B. I do not want ODR, because I do not want to receive routes through the dialer, for security reasons. The redistributed routes must be generated as statics in the access router (which is under my control), then redistributed into my OSPF, but depending on the state of the dialer pool.

Thanks in advance.

Kevin Dorrell

Luxembourg

7 REPLIES

Re: Routes to dialer interfaces

Reliable Static Routing Using Object Tracking should accomplish the desired outcome. The route won't exist in the routing table if the object tracked can't be reached. The question of static route getting redistributed into OSPF doesn't arise if the route doesn't exist in the routing table.

Here's the CCO link:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html#wp1071672

HTH,

Sundar

*Please rate all helpful posts.

Re: Routes to dialer interfaces

Sundar,

That is helpful, but it doesn't quite fit the bill. The example they give is pinging an IP address to track a remote oobject. In my case, the remote objects are on the other side of a dialer link, so it wouldn't really be appropriate to ping them in this way.

Is it possible, perhaps, to track an interface object instead? For example, I want the static routes to track the state of the ISDN PRI that is supplying the dialer pool for the dialer profiles. If the PRI is down, I want to remove any static routes that point to the dialer profiles.

My main problem is that dialer profile interfaces are always spoofed "up". If I have a static route to a serial line, and the serial line is down, then the static route disappears. If I have a static route to a dialer profile, and the dialer pool goes down, then the static route remains. I want it to disappear in the same way a route to a serial would.

Do you have any other ideas how I could achieve this?

Kevin Dorrell

Luxembourg

Re: Routes to dialer interfaces

Bump.

Does anyone have an idea how I could do this? I don't think I can do it by tracking a remote object because it is a dialup interface, and it would be too costly to dial every few seconds just to track the PRI availability.

To expand on the architecture, I have two sites: a main site and a backup site. The sites are connected together by a Gig link, so I can run VLANs between the sites. Dialin/dialout services must be assured at all times. My idea was to have a remote access router on each site, connected to the PTSN via a PRI. On the outside, the PRI provider can arrange to redirect the number if the main site is down.

Each remote access router has some static routes pointing to dialer profile interfaces. On the inside, each remote access router must redistribute these static routes into OSPF, with the main site having a lower metric than the backup site. But if the main site PRI goes down, the main site router must stop advertising its routes.

How can I achieve that, bearing in mind that the static routes point to spoof-up dialer interfaces?

Kevin Dorrell

Luxembourg

Re: Routes to dialer interfaces

Hello Kevin,

I think Ive already posted it before, but for the object tracking part.

just to remimd you that tracking can be done in different ways than just pinging.

Tracking the IP-Routing State of an Interface

Tracking the Line-Protocol State of an Interface

Tracking IP-Route Reachability

Tracking the Threshold of IP-Route Metrics

Check this link:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541be.html

Not all IOS and platform accept this feature though,

HTH,

please rate this post if it does,

Vlad

Re: Routes to dialer interfaces

Vlad,

Thank you. At first sight, that would seem to solve the problem. The previous poster was on the right track (no pun untended), but the 12.3 document mentioned only tracking by ICMP. Evidently I need my routes to track the state of my PRI. I shall study the 12.4 version of the doc today, and let you know if it fits.

On one hand its a pity because my router does not support 12.4 - it's an old 2610, with too little memory. On the other hand, it's a good thing because I now have a good reason to ask the management to buy me a new 2811!

Kevin Dorrell

Luxembourg

Re: Routes to dialer interfaces

This feature is not only IOS specific but platform too.

I'd recommend searching your router hardware on CISCO FEATURE NAVIGATOR.

Ive found 2610XM not sure if this is yours, but 12.3T already have this feature.

c2600-entbase-mz.12.3-8.T.bin for instance, 96mb dram/32mb flash

I ran into a problem trying to use this on CATALYST 4506. I've posted 3 posts here, looking for a solution, and no good.

Anyway, remember to rate any helpful post. I'd really appreciate

Thanks, Vlad

Re: Routes to dialer interfaces

Vlad,

Thank you for the information so far. I am almost there, but unfortunately none of my equipment supports the feature yet, so cannot play with the feature yet. (My 2610 is one of the older non-XM models.) So I have a couple more questions.

OK, so I understand how I can create a track object to represent the state of my ISDN PRI interface. I understand how I could use that track object to control the priority of HSRP, just like I used to when the feature was kind-of built into the standby coommand. But that is not quite what I am after.

What I need to know now is this: I have some static routes pointing to my always-up dialer interfaces. These statics are redistributed into OSPF. In fact, I have two routers doing this, and I want to choose the one whose ISDN line is working. Can I use a distribute-list and a route-map to influence their redistribution metric depending on the state of the tracked object, i.e.the state of the ISDN PRI? If so, can you point me to a configuration example how this might be done?

Thanks in advance.

Kevin Dorrell

Luxembourg

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