Subject: [Isis-wg] IP Reachable Address MIB table

From: "Suresh Boddapati" <[email-masked]>
Date: Wed, 27 Feb 2002 20:17:10

I am a little confused about the IP Reachable Address MIB table. The table 
description says
"The table of IP Reachable Addresses to networks, subnetworks or hosts 
either manually configured or learned from another protocol"

The indices of this table are SysInstance, CircIndex, IPRAType and 
IPRAIndex.

Can someone clarify the following:
1) What does manual configuration mean in this context? Is it referring to 
the internal reachability (the IP subnets of the circuits - represented by 
circIndex - on which ISIS is enabled)?
2) What does "learned from another protocol" mean in this context? Is it the 
redistributed routes from another protocol. If so, what is isisCircIndex 
doing as an index? Does it mean only those redistributed routes that can be 
reached over a ckt that has ISIS enabled on it?

Maybe I am totally off. Any help is appreciated. Thanks.

Regards,

Suresh

_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com

_______________________________________________
Isis-wg mailing list  -  [email-masked]
http://spider.juniper.net/mailman/listinfo/isis-wg

---

From: Jeff Learman <[email-masked]>
Date: Wed, 27 Feb 2002 18:34:21 -0500

At 03:17 PM 2/27/2002, Suresh Boddapati wrote:
>I am a little confused about the IP Reachable Address MIB table. The table description says
>"The table of IP Reachable Addresses to networks, subnetworks or hosts either manually configured or learned from another protocol"
>
>The indices of this table are SysInstance, CircIndex, IPRAType and IPRAIndex.
>
>1) What does manual configuration mean in this context? Is it referring to the internal reachability (the IP subnets of the circuits - represented by circIndex - on which ISIS is enabled)?

No, these are destinations that are called "reachable address prefixes" in
section 6.3 of 19589.  They are typically addresses that are outside the
routing domain (autonomous system in IP parlance), ones that are NOT
subnet addresses of directly attached subnets.

>2) What does "learned from another protocol" mean in this context?

An example would be if you're running BGP and IS-IS level 2 on the same
router (which would be a boundary intermediate system, BIS.)  BGP learns
about routes in the "outside world", IS-IS propagates this knowledge to
other L2 routers so that all L2 routers can figure out the closest BIS
serving that address.  (Note: with clever use of metrics it may be
possible to provide a shortest path to the destination, rather than a
shortest path to a BIS serving the destination -- I don't know.)

>Is it the redistributed routes from another protocol. If so, what is isisCircIndex doing as an index?

This is the index of the circuit leading to the router in the other
domain, serving the external addresses.

>Does it mean only those redistributed routes that can be reached over a ckt that has ISIS enabled on it?

No, the circuit does not have to be one that has IS-IS enabled.