[c-nsp] MAC-to-IP script on IOS

[Hansen, Ulrich Vestergaard B. (E W EN R&D DT ES 1 2)]

Hi All

Thank you very much everyone. Its simple and not at the same time. The ip address are NOT in the ARP table, and sometimes not active so collecting mac addresstable through snmp might not work. 

Ive got exactly what i was hoping for; some inspiration!
Thank you all for the help.

Sent from my iPad

On 25/05/2012, at 12.22, "Phil Mayers" <p.mayers at imperial.ac.uk> wrote:

> On 05/25/2012 07:27 AM, Hansen, Ulrich Vestergaard B. (E W EN R&D DT ES
> 1 2) wrote:
>> Gents,
>> 
>> Have anyone come across a script that could yield the IP address of a
>> given mac-address when invoked on a Layer 3 Router? I would assume
>> that you would have to select the given interface (as it could be any
>> interface) and the router should start arp-ing all hosts on a given
>> subnet returning the result when finished executing the script?
>> 
>> Assumptions is that you know the logical subnet where the mac-address
>> reside or maybe it could be invoked with a "all" interface command to
>> run the script on all logical interfaces. Anyone seen it?
> 
> This is such a simple question I feel sure I am misunderstanding it.
> 
> It seems you are assuming the IP will NOT be in the ARP table. If that's 
> the case, why do you assume that "arp"ing all hosts in a subnet would 
> make it appear in the ARP table.
> 
> Put another way: why do you need to know the IP of a MAC that *isn't* in 
> the ARP table?
> 
> You might want to investigate "netdisco" which maintains historical 
> IP/MAC mappings by way of the ARP table. We run something similar locally.
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