CSDiscovery: How to determine management IP and display name

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May 30th, 2008
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this is what I currently found about the new CSDiscovery and how the management IP and the Display Name are determined (mainly from what jclarke wrote on the forum);

I am not sure if it is correct and covers every aspect but *ANY* comment on this is highly appreciated


- I add it as an attachment so comments can be made if necessary -


I found a main difference for 'Resolve by Loopback' in the documentation and in some threads here on the forum.

In some threads it states that the lowest ifIndex determines which loopback is choosen - in the documentation I found the statement that it is the loopback with the highest address...

("If there are multiple loopback IP addresses, the highest loopback address is used to manage the device" - http://www.cisco.com/en/US/docs/net_mgmt/ciscoworks_common_services_software/3.1.1/user/guide/dcr.html#wp1469536)


WHAT IS CORRECT ??

????????

and if it IS the highest address, what is higher 19.61.20.75 or 119.61.20.75 - because sometimes alphabetical sorting is used (from a programmatically view)- an was used for most parts of LMS (at least until LMS 2.6)

????????


A LAST QUESTION:

Will the Discovery Filters now come into play AFTER the determination of the management IP or BEFORE (when the first IP of a device is found) ???



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Joe Clarke Fri, 05/30/2008 - 10:14
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It's important to realize that the behavior changed between Campus Discovery and CS Discovery. This violates POLA, but it's too late to change back now as that would mean another POLA violation.


CS Discovery looks for the highest IP address, and it does octet numeric comparisons so 119.61.20.75 > 19.61.20.75.


Your other question actually raises a bug of mine. I found that IP address INCLUDE filters come into play after the device is contacted, and its ipAddrTable and ifTable are polled. So, if any of the addresses on the device match the include filter, then they will be included (even though the management IP address might not be the one in the include filter list). Exclude filters apply before the device is contacted, and operate on the IP address by which the device entered Discovery.


The basic flow is:


* Apply Exclude IP address filter

* Poll ifTable

* Poll ipAddrTable

* Check filters

* Determine preferred management address

* Determine management hostname


The hostname is obtained if the preferred management address was found successfully, and the resolution scheme is loopback of sysName. If the preferred management address was not found, or the resolution scheme is by name, then a lookup is performed on the IP address by which the device was found.

m.sobolev Tue, 06/03/2008 - 23:16
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Is it possible to get the name of the devices by sysName (snmp). Not by DNS lookup?

Joe Clarke Tue, 06/03/2008 - 23:23
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This is not possible. While Discovery will poll sysName, it will still require that sysName be configured in DNS or in the server's local hosts file.

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