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Is it possible to get a remote client to send a DHCP-style request to a server (which you're on) to test the network routes are open? I can check from server to client, but different ports are used on the opposite direction (i.e. client to server). We're trying to avoid RDP-ing into the client to do this test.

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  • If you can get from the server to the client then a route indeed exists between the two.
    – joeqwerty
    Oct 2 '14 at 13:23
  • @joeqwerty I was under the impression that the ping packets return on different ports so proving it Server->Client is not the same as Client->Server since certain ports might be blocked on the firewalls. Or am I wrong?
    – Watters
    Oct 3 '14 at 7:48
  • Are you trying to determine whether a route exists between the two or are you trying to determine what ports are open on each end, because those are completely different things. The route is the physical path between the two endpoints, regardless of what ports are open. If you can get from the server to the client then a route (physical path) indeed exists. Now if you need to know what ports are open on each endpoint that's a different matter entirely.
    – joeqwerty
    Oct 3 '14 at 14:32
  • @joeqwerty I'm trying to make sure that a client can communicate with the DHCP server for DHCP requests and that this isn't blocked by any firewalls. (But I'm trying to do it without logging onto the client, but I can log onto the server, and trying to do it in advance of the DHCP server actually being used to allocate addresses)
    – Watters
    Oct 3 '14 at 16:08
  • OK. First of all, if these machines are on different networks then you'll need to set up a DHCP relay agent so that the DHCP client requests can reach the server. Secondly, if you're trying to do this across the internet then you may have problems with intermediate routers forwarding the DHCP traffic. Thirdly, DHCP clients don't send DHCP requests to a server (at least not during the initial DORA process), they broadcast a message to the local network to locate a DHCP server.
    – joeqwerty
    Oct 3 '14 at 16:18
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On *nix-based machines, way to go is dhcping:

dhcping -h CLIENT_MAC_ADDRESS -c CLIENT_IP -s SERVER_IP

you'd have to setup a fix address on the server, of course.

On Windows machines there's also a handy tool:

http://blog.thecybershadow.net/2013/01/10/dhcp-test-client/

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