Find ip address of connected device

[svetoslav141]

Hello,

I have to find the ip of a switch that is connected to an ISR.

How can I find this ip? Right now I only have the IP if the ISR and i can only log into the ISR but i need to log into the switch.

The connection between the 2 devices is with trunk on the switch.

[paul driver · Accepted solution]

Hello

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@svetoslav141 wrote:

The connection between the 2 devices is with trunk on the switch.

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If this the case then i assume the interface on the ISR has sub-interfaces correct?

ISR
sh arp <interface>x/x.y
sh cdp neighbor <interface> detail | in IP

[svetoslav141]

Thank you for  the provided information it was very useful.

[Seb Rupik]

Hi there,

Assuming the switch has an IP in a mangment VLAN and that VLAN is part of the trunk link, check the mac-address table on the ISE filtering for both the VLAN and the interface:

sh mac-address vlan <management_vlan_id> | inc <interface>

Now assuming your ISR has an IP in the management VLAN, you can then check its ARP cache and filter on the MAC address:

sh ip arp | inc <mac_address_from_previous_step>

cheers,

Seb.

[svetoslav141]

The problem is that trere are a lost of IPs in the arp table and i can't ssh tonone of them

[paul driver]

Hello

You should be able to filter on interface as shown, try those two commands i have posted, as for gaining ssh access you sure remote access is enabled for either ssh or telnet?

[Seb Rupik]

As shown, filter out the layer2 address from the mac-address using VLAN and interface. Once you have the mac-address select it from the ARP cache.

All being well you can filter from 000's to just one entry.

[paul driver]

@Seb Rupik 

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@Seb Rupik wrote:

As shown, filter out the layer2 address from the mac-address using VLAN and interface. Once you have the mac-address select it from the ARP cache.

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On a router?

[Seb Rupik]

Ah, I am too used to play with switching modules ;)

[paul driver]

@Seb Rupik 

TBH mate it may have sw module in so its still valid

[svetoslav141]

Hello,

Thank you for that it was really helpful.
I found the IP of the switch.