UDP packets to IP addresses other than specific ones not arriving and not shown in Wireshark

Posted by Max on Server Fault See other posts from Server Fault or by Max
Published on 2012-12-17T02:49:58Z Indexed on 2012/12/17 5:04 UTC
Read the original article Hit count: 486

Filed under:

firewall

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ip

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routing

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udp

I'm writing a service using UDP, but I can't manage to reply to the client.

When sending to the client via the DHCP-assigned IP (192.168.1.143) Wireshark shows no sent packets. The server receives and Wireshark shows any packet sent by the client (broadcasted).

If I send to a random, unassigned IP Wireshark doesn't show it. I thought the NIC would happily send it, since there is a router in the way - shouldn't Wireshark show it, even though it cannot possibly be received by a remote endpoint?

If I send to either the router IP or another (specific, there is only one other) computer, the packet is shown in Wireshark.

I am running Windows 7, the firewall is turned off using the control panel.

Does the fact that wireshark doesn't show these packets mean that they aren't sent? What reason could there be for showing packets to one IP, but not another, on the same subnet?

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