In our system, the Windows PC has two NICs, one for WAN and one for LAN (no gateway). For the LAN side, a Linux PC is connected through two switches. Also, switch2 is powered on/off with the Linux PC. (WAN)
        PC1 (Windows) (LAN)
        Switch 1
            | (below switch and linux pc are powered on/off together)
        Switch 2
            | (LAN)
        PC2 (Linux)


PC1 can ping PC2 ( successfully when the whole system powers on while PC1 can't ping PC2 if we only shutdown and re-power on the PC2 (with switch 2).

In this case:


通过最多 30 个跃点跟踪

  1     5 ms    11 ms     3 ms
  2     6 ms     1 ms     1 ms
  3     *        *        *     请求超时。
  4     *        *        *     请求超时。
  5     *        *        *     请求超时。
  6     *     ^C

In this case, when we re-plugged the PC1's NIC to the WAN (, PC1 will be able to ping PC2 successfully again.

Don't know why this happens since the route table doens't have any change before and after the re-plugging -- both have the line " 在链路上 266":

 17...0c c4 7a 0d c9 ad ......Intel(R) 82574L Gigabit Network Connection #3
 13...0c c4 7a 0d c9 ac ......Intel(R) 82579LM Gigabit Network Connection
  1...........................Software Loopback Interface 1
 12...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
 16...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2
 15...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface
IPv4 路由表
网络目标        网络掩码          网关       接口   跃点数
     10            在链路上    266            在链路上    266            在链路上    266            在链路上    306            在链路上    306            在链路上    306            在链路上    266            在链路上    266            在链路上    266            在链路上    306            在链路上    266            在链路上    266            在链路上    306            在链路上    266            在链路上    266

Also, in our another system, only the switch2 is provided (no switch1). The same problem doesn't happen there. The only difference I know is that in this another system the LAN side NIC would be deactivated when switch2 is powered off. (WAN)
        PC1 (Windows) (LAN)
            | (below switch and linux pc are powered on/off together)
        Switch 2
            | (LAN)
        PC2 (Linux)

Any suggestion is greatly appreciated.

closed as off-topic by Ron Maupin, YLearn Jun 13 '16 at 14:12

This question appears to be off-topic. The users who voted to close gave this specific reason:

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If this question can be reworded to fit the rules in the help center, please edit the question.

  • Welcome to NE, we hope you will both contribute to and learn from this community. NE is a site to ask and provide answers about professionally managed networks. This question seems to be more related to server/computer configuration which is off topic as defined by the community. Please see What topics can I ask about here? for more details. This does not appear to be a network problem. You could try posting this on a different site on the network, such as Super User. – YLearn Jun 13 '16 at 14:12

It appears that when you are performing the trace route, the path is taken out of your WAN interface rather than your LAN side.

Each time you are powering off PC2 and SWITCH2, you are clearing the learned routes on PC1 I think and only when you remove the WAN interface it will try to learn the path to PC2 because it's the only interface available. Once it has learned both paths, it can choose where to send the PINGS correctly based on the PC1's routing table.

What you could perhaps do is setup a static route on PC1 using the following command

route -p add mask IF <InterfaceNumber> metric 2

We are using as the nexthop so that we can tell Windows to use a specific interface. You can find the interface number listed when you route print.

Alternative you can specify PC2 as the next hop if there are no other PC's you need to get to using route -p add mask metric 2

Give this a go and see how this works for you. If this does not work, you can remove the static route using the following command

route delete

Hope this helps you on your quest.


  • Thanks, I'll give it a try the next day. Still don't understand why the static route would work differently with the " 在链路上 266" which exists even before I re-plugs the cable for the LAN side. – Gang Yin Jun 11 '16 at 0:13

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