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I have weird situation where a single machine on my home network can't access another. The network is provided by TP-Link WR841ND router to following machines:

  • A - 192.168.1.117 - Win8.1 machine, wired connection,
  • B - 192.168.1.200 - Ubuntu 12.04 server machine, wired connection,
  • C - 192.168.1.111 - Macbook, wireless connection,
  • D - 192.168.1.210 - Raspberry Pi, wireless connection.

The problem is that A and B can't ping each other, both with Destination host unreachable error.

  • A can ping C and D.
  • B can ping C and D.
  • C can ping A, B, D.
  • D can ping A, B, C.

If I take wireless dongle from D and use it on A, everything suddenly works - it's only when both A and B are connected via wired connection the problems arise.

arp -a on box A doesn't list B: Interface: 192.168.1.117 --- 0xa Internet Address Physical Address Type 192.168.1.1 *mac-address* dynamic 192.168.1.111 *mac-address* dynamic 192.168.1.210 *mac-address* dynamic

arp -a on box B lists A, but with <incomplete> where mac addresses of other devices are: A (192.168.1.117) at <incomplete> on eth0 C (192.168.1.111) at *mac-address* [ether] on eth0 router (192.168.1.1) at *mac-address* [ether] on eth0 D (192.168.1.210) at *mac-address* [ether] on eth0

arp -a on box C lists everything: router (192.168.1.1) at *mac-address* on en0 ifscope [ethernet] A (192.168.1.117) at *mac-address* on en0 ifscope [ethernet] B (192.168.1.200) at *mac-address* on en0 ifscope [ethernet] D (192.168.1.210) at *mac-address* on en0 ifscope [ethernet]

The router is running DD-WRT v24-sp2 (06/23/14) firmware. Resetting factory settings didn't help, neither did disabling SPI firewall, toggling AP isolation on or off, or poking other buttons in frustration.

Any suggestions?

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  • Can you post the revalant parts of IPCONFIG on the windows computer and IFCONFIG on the Linux machine? – Nate Sep 30 '14 at 19:33
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It turned out to be bug in DD-WRT router firmware. Appears that this old bug is back in builds dated after 29.03.2014

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  • Did upgrading the firmware fix it? – Seth Apr 28 '18 at 4:44
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On the router, you may want to check that both wired and wireless connection are on the same firewall zone (lan) and that both wired connection are on the same vlan, inside the lan firewall zone.

You may want to check one computer didn't ban the other automatically for some reason (aggressive blocking policy from some security solutions), did you try pinging machine B from A when running in safe mode with networking to exclude third services on the windows machine ? Did you try disabling firewall completely on both to test ?

This is not a strict answer, just some paths to poke on if you didn't already.

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