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

From: "Suresh Boddapati" <[email-masked]>
Date: Thu, 28 Feb 2002 00:32:37

I guess my whole doubt is related to the isisCircIndex being an index of the 
table. Per the MIB, isisCircIndex is defined as
"The identifier of this circuit, unique within the instance of the protocol. 
This object follows the index behavior. This is for SNMP purposes only and 
has no relation to any protocol value".

isisCircIndex is one of the indices into the isisCircTable.
Note this is not isisCircIfIndex which is a member of the isisCircTable (not 
an index) and is defined as
"The value of ifIndex for the interface to which this circuit corresponds. 
This object cannot be modified after creation"

Now if you say
>This is the index of the circuit leading to the router in the other
>domain, serving the external addresses.
and if ISIS need not be enabled on that interface, then how can there be an 
index for that interface because a  row corresponding to that interface does 
not exist in the isisCircTable.

If we take an example,

-------Router-------
   if1          if2
   ISIS

if1 has ISIS enabled which caused a row to be created in the Circ table with 
circindex say id1. if2 does not have ISIS enabled and therefore does not 
have any index corresponding to that circuit in the isisCircTable because 
the row does not exist.

If if2 is the interface leading to the external destination, how can you 
represent the circIndex for that interface.

One could argue this is implementation dependent; one could always create 
rows in the ISIS circ table for all the interfaces in the system and mark 
them as not in service, I suppose, but is this a good design of the MIB 
table? If all one wanted is to know all the external destinations that ISIS 
has learned from other protocol, why not index it without using the 
circIndex and list the outgoing interface as one of the members in the table 
and make it isisCircIfIndex instead of isisCircIndex? Am I missing 
something. Thanks.

Regards,

Suresh

>From: Jeff Learman <[email-masked]>
>To: "Suresh Boddapati" <[email-masked]>
>CC: [email-masked]
>Subject: Re: [Isis-wg] IP Reachable Address MIB table
>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.
> >
> >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)?
>
>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.
>
>
> >Maybe I am totally off. Any help is appreciated. Thanks.
> >
> >Regards,
> >
> >Suresh
> >
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---

From: "mukula" <[email-masked]>
Date: Thu, 28 Feb 2002 16:24:53 +0530

Hi all,
I am doing ISIS testing here. To test point-to-point functionality of ISIS I
am getting use of serial link of cisco router with ppp encapsulation.
At other side i am running pppd software freely available. so my doubt is
whether pppd support ISIS or not.
Because for this i think pppd has to negotiate OSINLCP (osi network layer
control protocol) in NCP phase of PPP, which pppd does not support.

Can any one help me out in this wheather i am correct or not.
Is there any other ppp freeware is available ?

Regards,
-Mukul

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]]On Behalf Of Suresh Boddapati
Sent: Thursday, 28 February 2002 12:33 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: [Isis-wg] IP Reachable Address MIB table

Now if you say

If we take an example,

-------Router-------
   if1          if2
   ISIS

Regards,

Suresh