Don't get me wrong.  There are definite times to use ISIS, there are 
definite times to use OSPF, and there are times either will work just 

>Russ Meyer <[EMAIL PROTECTED]> wrote
>IS-IS is considered more stable because you can manually set the refresh
>time as far out as 18 + hours.

This is desirable when the underlying routers and links are stable, 
which is the typical case inside a provider network. A widely 
distributed enterprise network, however, may need a reality check 
more frequently.

>Also, it is more secure, because routing
>updates are transmitted via a layer 2 transport, (CLNS).

True, ISIS runs over the data link layer (not CLNP). In one sense, 
you can argue that is more secure because updates are limited to one 

But OSPF and EIGRP have their IP hop count set to 1, so that will 
limit them to one link as well.

>Also, IS-IS can
>support over 850 routers in a single area.

The more basic question is when is it desirable to support that many 
routers in a single area? It can be appropriate in some provider 
networks, but it tends to be a terrible idea in enterprise networks. 
That being said, there's at least one highly tuned OSPF network that 
runs 1000 or so routers in area, generally an insane idea. 
Most carriers using ISIS, according to Dave Katz, use a single area.

>Try doing that with OSPF, also
most enhancements that are added to OSPF are also added to IS-IS.

Basic ISIS non-backbone areas behave like OSPF totally stubby areas. 
Obviously, there are cases in which totally stubby areas are very 
useful.  It's only recent, however, that there's starting to be 
controlled L2 injection into ISIS level 1 areas.  Without such a 
feature, you are limited to a cold potato/closest exit routing policy.

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