Rediscovering Switches

Answered Question
Jun 6th, 2008

Hello,

In user tracking, all host names and IP addresses went away (6000+ devices). Thinking it was an issue with my device discovery (switches, in particular) I deleted all of the switches (thinking) that it would rediscover them. After several discoveries, the switches have not come back. What can I do to resolve these issues?

I have this problem too.
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Correct Answer by Joe Clarke about 8 years 6 months ago

This tells me that you're using two CDP seed devices, .13 and .15. You've configured a hop count of 2, so this means that these seed devices plus all devices that are at most two hops away will be discovered (and no further). So, make sure that all the devices you want to discover are within two CDP hops of these two seed devices. If you need to go further, increase or remove the hop count.

Also, you're using one SNMP community string for all devices. Make sure this is the correct community string. Even though you've configured default credentials, Discovery will only use the one community string you've configured in its SNMP Settings screen.

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David Stanford Fri, 06/06/2008 - 05:00

What version of LMS?

You can add seed devices and run a discovery to map out the topology again. How many seeds have you added?

davepeat2 Fri, 06/06/2008 - 05:04

I have added three. One is the core that owns all of the networks.

Joe Clarke Fri, 06/06/2008 - 08:46

Actually, for CDP discovery, we do recommend a core or distribution switch as they tend to have the most CDP neighbors, and can kick off multiple parallel threads more quickly. For other algorithms, a router may be preferred.

davepeat2 Fri, 06/06/2008 - 09:04

Neither way seems to be working. It's as if since it knew them and I deleted them it won't discover them again. I did not exclude them but that's how it is acting. Any suggestions?

Joe Clarke Fri, 06/06/2008 - 09:06

You're mixing terminology here. It sounds like the problem you're facing is solely with UT. That is, you're missing IP and hostname data for your end hosts. If so, this has nothing to do with discovery.

Just so we're not trying to troubleshoot the wrong problem, please post a screenshot which illustrates your problem as it is now.

davepeat2 Fri, 06/06/2008 - 09:18

Actually, I have two problems.

First, my switches are not being discovered. I deleted them yesterday afternoon.

There is no "Switches" category - which there used to be.

Second, I am missing the Hostname and IP in UT. That is why I deleted my switches in the first place. I thought that might have been the reason.

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Joe Clarke Fri, 06/06/2008 - 09:27

You have LMS 3.0, but what version of Common Services and Campus Manager do you have?

Joe Clarke Fri, 06/06/2008 - 09:37

Please post NMSROOT/conf/csdiscovery/CSDiscovery-conf.xml file.

Correct Answer
Joe Clarke Fri, 06/06/2008 - 09:59

This tells me that you're using two CDP seed devices, .13 and .15. You've configured a hop count of 2, so this means that these seed devices plus all devices that are at most two hops away will be discovered (and no further). So, make sure that all the devices you want to discover are within two CDP hops of these two seed devices. If you need to go further, increase or remove the hop count.

Also, you're using one SNMP community string for all devices. Make sure this is the correct community string. Even though you've configured default credentials, Discovery will only use the one community string you've configured in its SNMP Settings screen.

davepeat2 Fri, 06/06/2008 - 10:25

O.K., now I didn't change the read community string and it is starred out so I can't verify, but I re-entered it and now it is discovering my switches again. It shouldn't have changed - but I guess the end justifies the means!

Thanks for all your help!

Any idea about the Host names and IP addresses in UT? They used to be there. I checked the server and it can resolve and does have the correct DNS servers specified.

Joe Clarke Fri, 06/06/2008 - 10:29

IP and hostname information in UT has nothing to do with the switches. This is all dependent on having routers data collected which have the ARP entries corresponding to the end host MAC addresses in UT. So, check the Campus Manager Topology Map, and make sure your routers are all showing up with green router icons.

If the routers are there, then perform another UT acquisition, and the IP addresses should show up. The hostnames will then be derived from the IP addresses using DNS or local hosts file name resolution. So make sure your DNS is properly configured on your server.

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