MAC to IP matching

Started by jvz

jvz

MAC to IP matching   31 December 2016, 02:03

Hi all,

I just bought 2 of you programs (Network Scanner and Switch Port Mapper) and I think they Network Scanner has a feature that can make Switch Port Mapper more powerful.

Let me explain:
The Switch Port Mapper needs access to a router to do MAC to IP matching using the ARP table from the router (logical because the router "knows" all IP addresses and the MAC address that uses it), but what if SNMP is not enabled on the router or there is no router on the network (unlikely nowadays but anyway)?

Network Scanner scan the network and build its own MAC and IP table. What if that feature was build into Switch Port Mapper? I know it will take more time but Network Scanner does a real good job resolving the info.

grtx Johan
SoftPerfect Support forum - Andrew avatar image

Re: MAC to IP matching   31 December 2016, 10:26

Hi Johan,

This functionality is already present. You can turn it on and off in the settings as shown below:

SoftPerfect support forum

When it is turned on and no router information is provided, the Port Mapper will scan your local subnet for MAC-to-IP address mappings. If you are connected to more than one network, it will display a pop-up asking to choose which network to scan:

SoftPerfect support forum
jvz

Re: MAC to IP matching   02 January 2017, 21:20

Hi Andrew,

I already ticked that option on but what if the application is located on a different subnet, the switch is queried correctly but no mapping can be done due to local ARP cache is only local to the subnet

grtx Johan
SoftPerfect Support forum - Andrew avatar image

Re: MAC to IP matching   02 January 2017, 23:04

Unfortunately it's only possible to obtain MAC-to-IP-address mappings within the local subnet.

Unless specifically configured, a router doesn't forward ARP traffic, which makes it impossible to find out the MAC address of a device in another network. There's a bit of discussion about getting a MAC address of an IP address from behind a router, if you are interested in details.
jvz

Re: MAC to IP matching   03 January 2017, 19:05

Hi Andrew,

That's exactly my point, why not build the networkscan from networkscanner into switch port mapper to actively get the ip/mac and cross-reference them with the switch.

grtx Johan
SoftPerfect Support forum - Andrew avatar image

Re: MAC to IP matching   03 January 2017, 20:22

As I explained in my message earlier, it's not possible to reliably resolve IP address to MAC addresses in a different subnet. Our Port Mapper and Network Scanner use a similar code, with one exception:

Port Mapper resolves IPs to MACs with:
  1. ARP scanning
  2. Query router with SNMP

Network Scanner resolves IPs to MACs with:
  1. ARP scanning
  2. Query router with SNMP
  3. NetBios datagrams

Methods (a) and (b) are identical, but method (c) allows us to get MACs from some Windows machines (only) that have NetBios enabled. Is this what you want see ported from Network Scanner to Port Mapper?
jvz

Re: MAC to IP matching   03 January 2017, 21:23

Hi Andrew,

because most end-points are windows computers in our orginazation it would be a great benefit to have this feature, so yes if it is possible .. at the moment I need to cross-reference them by hand which is very unpractical

grtx Johan
SoftPerfect Support forum - Andrew avatar image

Re: MAC to IP matching   04 January 2017, 18:23

Please try the latest build, it now uses NetBios to obtain MAC addresses and host names that are not accessible otherwise.

Granted your Windows computers have file sharing enabled, this should reveal at least some MAC addresses.
jvz

Re: MAC to IP matching   06 January 2017, 19:13

Hi Andrew,

you probably meant IP addresses, but yeah it works, it takes a while to resolve the ip addresses and hostnames but this is a valuable addition to the program. btw it is not confined to windows computers only even printers / and polycom telephone devices report their ip address (they even report their LLDP)

the only remark I have is the network scanning box, maybe you should add the ip subnet where the managed switch belongs to.

thank you very much for this great addition.

grtx Johan
SoftPerfect Support forum - Andrew avatar image

Re: MAC to IP matching   07 January 2017, 13:24

No worries, it's also a great idea to add the switch's network in the network scanning dialog. We've implemented that in the latest update.

SoftPerfect support forum

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