To identify IP host port for the L2 switch?

There is a remote end point connection diagram: router->switch->host s
On the switch:
raised DHCP server
is enabled DHCP snooping,
The IP host is bound or if it is set to statics added to exclude.

Added another host(Win), it's all set to static and set the IP from those that have already been issued or is bound, i.e. there is a conflict of IP addresses. Famous port of and MAC. How to determine what IP it is set?

PS the Task is not as simple as it seems. The host can be shipped, but look at it IP impossible. In ip dhcp conflict it shines not, because DHCP discover when enabling no host(IP is set to static)
3 answers
July 4th 19 at 23:04
Solution
In short the solution was)).
In the ARP table of the router will be only one match MAC/IP because the host when enabled, sends ARP for 0.0.0.0, and finds that the IP that is assigned to it is already on the Internet, then it assigns itself an IP network 169.254.0.0/16. No matching MAC and IP for this host in the ARP I will not find.
What I did: Raised the L3 on the router from the range 169.254.0.0/16, the computer gives me arp:
Protocol Address Age (min) Hardware Addr Type Interface
Internet 169.254.0.1 - 0006.52 bd.XXXX ARPA Vlan1000
Internet 169.254.248.116 1 001f.c68b.XXXX ARPA Vlan1000

I natu on the outside interface and route 169.254.248.116 am able to announce/32 with the router itself.
And RDP fail on this host and accordingly change/look desired IP
July 4th 19 at 23:06
As an option - pinguim network range (scanning range). then "arp -a >arp_table.txt" from there Graham ip mac. So you can see who else belongs to this guy
Access to this host and others are not. This feature only works on Router and switch - Alexander.Brek commented on July 4th 19 at 23:09
and I'm not talking about the host. a managed switch has a command to display the arp table - Gillian_Trantow commented on July 4th 19 at 23:12
Did so already, there should be two entries
IP MAC
192.168.1.10 XXXX.XXXX.XXXX
192.168.1.10 XXXX.XXXX.YYYY
But in the table there are records with the IP odinakovym - Alexander.Brek commented on July 4th 19 at 23:15
he mac address of the desired appears in the table? - Gillian_Trantow commented on July 4th 19 at 23:18
On the switch there is only the comparison of the port-MAC. About the IP he knows nothing, sees only the router. - morris commented on July 4th 19 at 23:21
cool. now artificially created conflict - ping -a [ip] was allowed in the name of the new and the mac the old ones. - Gillian_Trantow commented on July 4th 19 at 23:24
In short the solution was)).
In the ARP table of the router will be only one match MAC/IP because the host when enabled, sends ARP for 0.0.0.0, and finds that the IP that is assigned to it is already on the Internet, then it assigns itself an IP network 169.254.0.0/16. No matching MAC and IP for this host in the ARP I will not find.
What I did: Raised the L3 on the router from the range 169.254.0.0/16, the computer gives me arp:
Protocol Address Age (min) Hardware Addr Type Interface
Internet 169.254.0.1 - 0006.52 bd.XXXX ARPA Vlan1000
Internet 169.254.248.116 1 001f.c68b.XXXX ARPA Vlan1000

I natu on the outside interface and route 169.254.248.116 am able to announce/32 with the router itself.
And RDP fail on this host and accordingly change/look desired IP - Alexander.Brek commented on July 4th 19 at 23:27
: if that can not be repeated, we both see both lines :). Then unfold and the intrigue that piece of hardware? - Gillian_Trantow commented on July 4th 19 at 23:30
Have sublinual comment to response to the notifications affected.
Nothing supernatural:
router - cisco 2811
switch - 2960 lan base
PC win 7 - Alexander.Brek commented on July 4th 19 at 23:33
so for me, too, 2960, only sh arp, it shows the corresponding Mac and IP addresses. - Gillian_Trantow commented on July 4th 19 at 23:36
if I'm driving in the car, half an hour will be able to properly respond - Gillian_Trantow commented on July 4th 19 at 23:39
router 2851 - Gillian_Trantow commented on July 4th 19 at 23:42
You carefully read the conditions of the problem. You receive the host in the network with the IP(set statically), which is already assigned to another host in the network. Since this IP is already there, the OS will assign it an IP from the pool 169.254.0.0/16, above I described. So I've been told that the task was not as simple as it seems - Alexander.Brek commented on July 4th 19 at 23:45
Well, Yes. Called both busy. Find out FE, which is occupied through the static compliance of the Mak, Yip put in the exceptions and our DHCP piece of iron gets the FE of the allowed pool non-confrontational. Not? - Gillian_Trantow commented on July 4th 19 at 23:48
After a match of the Mac??? Again, if the host(Win) set the IP statically, it sends ARP for 0.0.0.0. It sees that this IP is busy and the OS naznachat him IP from the range 169.254.0.0/16. No corresponding WT host and given him the IP in the ARP table will not be - Alexander.Brek commented on July 4th 19 at 23:51
OK. Now compulsory dance will end and I'll try to simulate the situation on a real piece of hardware. In office as if no one is, even if you break, tomorrow morning, correct. :) - Gillian_Trantow commented on July 4th 19 at 23:54
Looks like I just lost a physical machine, the main thing tomorrow before anyone else in the office to appear. But the basic idea understood/the challenge felt :) it's called "the hard way". Well or to try Your method, which is called "test practice". But on the basis of everyday logic - the direction most likely correct. By the way, I never thought that "static" such a mess in DHCP networks. Somehow not accounted for.... - Gillian_Trantow commented on July 4th 19 at 23:57
July 4th 19 at 23:08
If you know MAC, look at the router's ARP (show arp table) directly after the scan the entire DHCP range
Did so already, there should be two entries
IP MAC
192.168.1.10 XXXX.XXXX.XXXX
192.168.1.10 XXXX.XXXX.YYYY
But in the table there are records with the IP odinakovym - Alexander.Brek commented on July 4th 19 at 23:11
But You said that MAC is known for - filter the output on it - Gillian_Trantow commented on July 4th 19 at 23:14
In short the solution was)).
In the ARP table of the router will be only one match MAC/IP because the host when enabled, sends ARP for 0.0.0.0, and finds that the IP that is assigned to it is already on the Internet, then it assigns itself an IP network 169.254.0.0/16. No matching MAC and IP for this host in the ARP I will not find.
What I did: Raised the L3 on the router from the range 169.254.0.0/16, the computer gives me arp:
Protocol Address Age (min) Hardware Addr Type Interface
Internet 169.254.0.1 - 0006.52 bd.XXXX ARPA Vlan1000
Internet 169.254.248.116 1 001f.c68b.XXXX ARPA Vlan1000

I natu on the outside interface and route 169.254.248.116 am able to announce/32 with the router itself.
And RDP fail on this host and accordingly change/look desired IP - Alexander.Brek commented on July 4th 19 at 23:17

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