How and which device IP is collected by DCR during discovery ?

[aringanisation]

we have more than 200 routers in our network, I have checked the Prefered Management IP  option to None . after discovery was finished some devices are discovered with their lookpack address some of them with their FastEthernet0/1 address !!

I would like to know how DCR collects device IP's ?

Thank you 

[Vinod Arya]

Hi Ali,

You can check these documents which talks in-depth about Ciscoworks Discovery Process :

Working with Common Services Device Discovery

Understanding LAN Management Solution (LMS) Discovery

Hope it helps.

-Thanks

Vinod

[Michel Hegeraat]

It will pick the device IP address, it learns from the CDP table of a previous learned, other device. If that IP address is the first time it see that device then it will use that address as the management address.

Cheers,

Michel

[aringanisation]

Let me shed a light on my scenario;

I have a seed device Number1( 192.168.100.1 ) which has CDP neighbor device Number2 with IP of 172.28.0.1 (which was unnumbered for loopback12)on serial link between them.

so Number1 knows Number2 with CDP neighbor IP of 172.28.0.1, so LMS will add 172.28.0.1 from seed device of 192.168.100.1. if I change the serial IP to be unnumbered from loopback12 to fastethernet0 which its IP is 10.0.1.2 then the neighborship between Number1 and Number2 will change, and Number1  knows Number2 with the IP of 10.0.1.2.

my question is if this happens after discvoery will LMS add duplicate devices because the device IP has changed ??

thank you

[Michel Hegeraat]

LMS will see the new IP 10.0.1.2 but it will query that device IP Table and then find it also has the IP 172.28.0.1 which is a known device so it won't add the device again and keep the previously found address.

Cheers,

Michel

[aringanisation]

Thank you Michel,

If it is a must to change the IP address of the device which is known by LMS, what should I do ?? Although I changed the device IP address (device identity in DCR) , after discoery it will automatically change to its previous IP.

thank you

[Michel Hegeraat]

In my understanding it will not change the IP address

If you alter the IP addres in LMS, and the device is discovered via another IP address, then the IP table will contain the IP address under which LMS already knows the device. LMS will keep that address.

However, if you delete the device then it may get rediscovered with another IP address, since LMS has no preference.

That is why I create a DNS or Hosts entry for each device with the IP address I want LMS to use for management and the device name, which is the same as the systemname/hostname on the device.

I then tell LMS to resolve the system name and use that as the prefered management IP address during discovery.

Cheers,

Michel

[Vinod Arya]

Your settings are being changed due to your Discovery Settings.

Make sure you dont have Update DCR Display Name check box selected in LMS Discovery Global Settings in both Discovery Setting and Discovery Schedule, as Schedule discovery has its own independent settings.

Which will restrict the chnages once you custom update the Device Display Name in DCR:

-Thanks

Vinod