make correspondance

[shinji7800]

Hello I have an architecture like this : 

Two L3 switchs (C6506) and access switches (C3750x) are connected on my C6506. My access Switch(AS) works by two and generally manage only one VLAN (one VLAN by specific application).

On my access switch there are host but I don't know their IP@

So I would like to find a way to make a correspondance with access switch port, mac @ and IP@.

I took ARP table from my C6506, Mac address table from 3750 and trunk interfaces from 3750.

To make a good correspondance I think to take @mac in mac addresse table who is not learned by a trunk interface, looking for it in the ARP table, and finally find is IP@@

Do you think it is the best way. there are risks to make correspondance like this ?

best regards.
I'm French, I apologize for my approximate English.

[Jon Marshall · Accepted solution]

If I understand you want to work out which port an IP address is on ?

If so assuming your 6500s are doing the inter vlan routing then -

1) check the arp table on the 6500 HSRP active switch and find the mac address of that IP

2) check the mac address table of the 6500 and see which port it is recorded on.

That port will probably lead to an access switch so use "sh cdp neigbor detail" to get the IP address of the access switch.

3) connect to the access switch and look for the mac address in the mac address table and this should give you the physical port.

If I have misunderstood your question please clarify.

Your English is much better than my French :-)

Jon

[shinji7800]

thanks a lot for your reply !

that's exactelly what I did. so there is not an another way to do it !

it is possible to make a interpretation mistake ?

P.S.:  cdp is disable on our network (security I guess)

[Masoud Pourshabanian · Accepted solution]

Hello,

Jon just memtioned CDP to find out the IP address of a specific switch. If you have a map of your network and switch connections and IP addresses, you can find out the IP addresses of other switches easily.

I you just chech ARP table, you might miss some mac addresses so if you can complete somehow your ARP table, the precedure has better result. You can go on your 6500 switches and ping for example 192.168.1.255(broadcast address). All clients with the IP in that range will reply so your arp table will have more entries.

Another way is using wireshark (packet sniffer) and inspecting ARP packets.

Masoud