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Two LAN Connections (Local + Internet), Suddenly Can't Access Internet

Tags:
  • NAS / RAID
  • Connection
  • Networking
  • Ethernet Card
  • Internet
Last response: in Networking
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September 26, 2014 6:09:36 AM

Here's the situation:

  • Windows 8.1 Desktop PC with two gigabit ethernet connections
  • DSL modem/ router
  • Asus Gigabit Switch
  • Synology NAS box with two gigabit ethernet connections


  • Since I need to access files on the NAS all the time, I have one ethernet port on the PC set to 192.168.4.x, with a direct connection to one port on the NAS also set to 192.168.4.x.

    The DSL modem/router is on 192.168.2.x - and both the PC and NAS have their other ports set to 192.168.2.x.

    For a long time this setup has worked really well - fast NAS connection, and able to connect to the internet no problem. Then this week (probably Thursday) following a reboot I lost the internet connection. Now, I can only connect to the internet if I disable the ethernet connection to the NAS.

    I'm not sure what changed, but there must be some way to handle or manage the routing so that internet traffic is sent through the 192.168.2.x port, right? I'm not sure why the PC suddenly started trying (and clearly failing) to access the web via the local connection.

    Thanks!
  • More about : lan connections local internet suddenly access internet

    September 26, 2014 6:17:51 AM

    What is your default gateway set to? It should be 192.168.2.xxx. You don't have a DHCP server on the NAS as well as the router do you?
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    September 26, 2014 6:48:48 AM

    Kanewolf is onto something and it's coming from the end going to the NAS.

    Make sure DHCP is off and your IP's are set statically
    You could use it the following way

    Computer Setting:
    IP 192.168.4.1
    subnet 255.255.255.0
    Gateway 192.168.4.2

    NAS
    IP address 192.168.4.2
    Subnet 255.255.255.0
    Gateway 192.168.4.1
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    Related resources
    September 26, 2014 7:02:12 AM

    Beachnative said:
    Kanewolf is onto something and it's coming from the end going to the NAS.

    Make sure DHCP is off and your IP's are set statically
    You could use it the following way

    Computer Setting:
    IP 192.168.4.1
    subnet 255.255.255.0
    Gateway 192.168.4.2

    NAS
    IP address 192.168.4.2
    Subnet 255.255.255.0
    Gateway 192.168.4.1


    Here is the Microsoft help for having multiple networks...
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    September 26, 2014 8:41:09 AM

    This is interesting ... nether Ethernet connection is holding the values. They were set manually, and I went to verify them again and found they were set to Obtain Automatically. However, Status still shows them using the correct settings.

    I'm going to try reinstalling the device drivers, and I'll check out the article @kanewolf linked to.
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    September 26, 2014 10:12:03 AM

    Well, I got it working - for just a minute.

    After all the clever stuff I tried didn't work I went back to basics and uninstalled both devices. Reboot, detected, re-installed, done. Right? But the connections were both set to DHCP, so I had to set the local connection the NAS to a static IP. Done, still working.

    Lastly, the ethernet connection for the network & internet had to be set to static because there are a number of incoming port forwarding rules that apply to that specific IP address. I made that change, and was right back to where I started - lost all internet connectivity (until I disable the NAS connection).

    So, no further along yet.
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    September 26, 2014 10:35:54 AM

    Make sure you only have a default gateway on the connection that goes your internet. If you are learning a default gateway via DHCP that you do not want you can use the ROUTE DELETE command from a CMD prompt you launch in admin mode.
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    September 26, 2014 11:37:08 AM

    Thanks, @bill001g, good idea but no joy.

    Ethernet 2 (connected to swtich -> router/modem)
    Manually set to:
    IP 192.168.2.100
    Mask 255.255.255.0 (also tried 255.255.0.0, as we have a some devices on 192.168.3.x, but that's another story)
    Gateway 192.168.2.1 (router)

    Ethernet 3 (direct to NAS)
    192.168.4.100
    255.255.255.0
    gateway empty

    Both are set to use 8.8.8.8, 8.8.4.4 for DNS. (also tried leaving DNS blank on Ethernet 3)

    It does appear this might be some kind of DNS issue, as I can connection to devices on both subnets, and on the internet, when both connections are active ... but can't pull up anything by domain name.
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    September 26, 2014 11:43:31 AM

    Forgot to mention, the "route print" command shows only one persistent route (I deleted all, added back 0.0.0.0, 0.0.0.0, 192.168.2.1, 1).
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    September 26, 2014 11:44:44 AM

    netstat /r in a cmd shell will show you all the routing information.
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    !