[CentOS] Network conections problems

[Anthony K]

On 23/02/17 17:54, Anthony K wrote:
> On 23/02/17 08:27, Rommel Rodriguez Toirac wrote:
>> The solution was another IP address to this network device and then 
>> everything work fine.
>>   Why this happend? How I can erase the link beteewn MAC 
>> 00:1D:09:FF:44:4B and IP 192.168.41.4? Where can be stored this link?
>>   Right now in the network is not assignet the IP address 
>> 192.168.41.4 to no one device (printserver, switch, router, 
>> workstation or server) and still whe I make arping have the answer:
>>
>> rommel at p6:~$ arping 192.168.41.4
>> ARPING 192.168.41.4 from 192.168.41.6 enp3s0
>> Unicast reply from 192.168.41.4 [00:1D:09:FF:44:4B]  0.631ms
>> Unicast reply from 192.168.41.4 [00:1D:09:FF:44:4B]  0.623ms
>> Unicast reply from 192.168.41.4 [00:1D:09:FF:44:4B]  0.623ms
>> Unicast reply from 192.168.41.4 [00:1D:09:FF:44:4B]  0.691ms
>> ^CSent 4 probes (1 broadcast(s))
>> Received 4 response(s)
>
> One thing to try if you have access to the switch where all the 
> devices are plugged in:
> *$ sudo ping -f 192.168.41.4*
>
> Then watch the switch for a lot of activity on 2 ports - the one you 
> are plugged into and another.  The other busy port will be the one 
> that's causing you grief.  If you have daisy chained switches, then it 
> might take a little longer to track it down.
>
> Happy hunting - :).
> _______________________________________________ 
Another solution, if you are the admin with access to the router, is to 
null route the packets from that IP.  The person using that device will 
let you know shortly after (lack of Internet access is the quickest way 
to get the attention of users on the network):

$ sudo ip r a blackhole 192.168.41.4