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New Member

ISIS Routing. Max areas.

I am currently researching a management/dcn solution for managing network elements, which use the OSI protocol (Alcatel Litespan Nodes)

I am intending to transport the OSI management link via an atm pvc to a central site terminating on a Cisco 3662 router (Telco option).

Potentially there could be up to 250 atm subinterfaces configured, which are mapped to the above managemnt links (pvc's).

My intention is to configure ISIS routing on each sub interface (atm pvc) and have each network element in its own unique isis area.

I also will need to configure under the "router isis" process a NET for each terminating isis area. This potentiall could result with up to 250 NET's being configured.

1/ Is this a viable solution using the 3662 with the Telco feature and extending the "max-area-addresses" under the "router isis" process to cater for the no. of attached area's ?

2/ Are there other options I should persue ?

3/ If 1 above is a viable solution, will each network element in each of the unique areas cache info about the other network elements in those area's other than itself's area.


Re: ISIS Routing. Max areas.

1. You cannot, even with the Multiarea feature , configure 250 Areas per router.

2. Other options would be something like this.

Have your 3662 be in one area

Have routers that terminate your Atm pvc (Assume this is the case) be in

one of your 250 management areas (L2 only to the 3662 and L1 to your

Managed devices)

3. 1 is not a viable solution since that many (250) areas cannot be defined on one router. Devices in one area do not cache things within another outside of it's own area. L1 devices within an area only know about devices within and the router, that will allow it outside of it's area by using the Attach bit in the LSP.

Hope this helps you,


New Member

Re: ISIS Routing. Max areas.

Don ...

Thanks for the info.

I had an inkling that this solution was not viable, but needed to confirm.

Would terminating the atm vc's on a single router (3662 Telco) and then setting the pvc's up such they were in say 3 bridge groups and configuringing 3 area addresses on the router work ?



area 1 --- 80 pvcs in bridge group one


area 2 --- 80 pvc's in bridge group two


area 3 --- 80 pvc's in bridge group three

What is the max recommended area's that the 3662 telco router can support ?

Many Thanks.


Re: ISIS Routing. Max areas.

Three areas can be supported normally without multiarea feature enabled on a router. Multiarea will allow up to 20 something areas but only one L2 instance and all the rest are L1 only.

Bridging in your solution would make me very nervous, in your solution. I would say that you could terminate all 250 ISO devices (assuming they could all play in 1 (or up to 3 areas) area with L1's to each. 250 ESs are alot but should be able to work.

My intial proposal with having your 3660 in one area L2 to the rest of your routers and L1 from your routers to your end devices is the way I would do it. This would enable Multiarea support and conform to ISO design.

Hope this helps you,


New Member

Re: ISIS Routing. Max areas.

Don ....

Many thanks for your advice/info.

We currently have an OSI network based on the "Cisco" model, but run ISO-IGRP within its core to allow for filtered re-distribution between ISIS and ISO-IGRP and works well.

However with the introduction of these new network elements, they have introduced difficulties when trying to integrate them into our current network, hence the options of exploring other alternatives.



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