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IMC Discovery Gets Netmask Wrong

 
James-A-Robbins
Frequent Visitor

IMC Discovery Gets Netmask Wrong

For two UPSs on my network IMC Auto Discovery got the netmask wrong.  I have checked the UPSs and they are configured correctly.  Other UPSs of the same model show the correct netmask.  Can I edit the incorrect entries?  Where is IMC picking up this incorrect information?

6 REPLIES
Neelixx
Frequent Advisor

Re: IMC Discovery Gets Netmask Wrong

James, any way you can include a screenshot to show what you are looking at?

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Aaron Paxson
@Neelixx
James-A-Robbins
Frequent Visitor

Re: IMC Discovery Gets Netmask Wrong

Here is  a screen shot showing 5 network address masks where there should only be two (128.146.232.0/21 and 172.24.0.0/16).  The 128.0.0.0/8, 128.146.0.0/16 and 172.0.0.0/8 addresses all have bad net masks.  When I check the devices they are setup correctly.  There does not seem to be a way to edit the database to correct this.

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James A. Robbins

 

Neelixx
Frequent Advisor

Re: IMC Discovery Gets Netmask Wrong

I'm guessing here... and this is only a guess.... 

 

Is it possible that the iMC is scanning routing tables of neighboring routers or systems?  If so, it may find those routes/networks via SNMP discovery.  Looking into the routing tables of systems.

 

This is common, because routers often summarize networks.  

 

Maybe the iMC found the summary network, and is putting those devices into it?  Or, maybe 1 device has an improper netmask, and iMC is grouping the other devices into the larger network?

 

Without knowing much of your network, it's hard to say.

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Aaron Paxson
@Neelixx
James-A-Robbins
Frequent Visitor

Re: IMC Discovery Gets Netmask Wrong

I don't have the credentials to have access to the router so I don't think it is supplying any information to IMC.  Maybe it is getting bad info from some ARP table or routing table in a device?

 

In any case I sure wish there were an easy way to correct the misinformation.

 

I just tried deleting one of the devices then re-discovering it, specifying the netmask.  It added it again with no net mask.

--

James A. Robbins

 

Neelixx
Frequent Advisor

Re: IMC Discovery Gets Netmask Wrong

I'm not so sure that it affects the operations in a negative manner, other than just being annoying.  It looks like it's just summary info.

 

From the config_db database:

 

select dev_ip_mask from imc_config.tbl_dev where dev_ip = '1.2.3.4';

 

update imc_config.tbl_dev set dev_ip_mask = '255.255.255.0' where dev_ip = '1.2.3.4';

 

This fixed the problem, but as soon as you hit "synchronize" and "refresh", it goes back.  That tells me it's getting it from somewhere on the device.

 

So, I did a packet capture after a "synchronize" and found that it's getting the data using SNMP from RFC1213 MIB in the ipaddrTable.  (1.3.6.1.2.1.4.20.1.3.10.8).

 

I hope this helps.

 

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Aaron Paxson
@Neelixx
James-A-Robbins
Frequent Visitor

Re: IMC Discovery Gets Netmask Wrong

Thanks for the help.  At least now I know where it is coming (or not coming) from.

I'll check the devices that are sending the wrong info a bit closer.

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James A. Robbins