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Hi, I've got a dual port Nic on my server. I'm using port 1 to push data to my remote box and port 2 for accessing the unit over web ...
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  1. #1
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    Question dual port


    Hi,

    I've got a dual port Nic on my server. I'm using port 1 to push data to my remote box and port 2 for accessing the unit over web interface. But i'm noticing reduced performance when data is being transmitted, so wondering whether data is being pushed through port 2 as opposed to port 1. Is there anyway to find out?
    Any linux commands that could help me here?

  2. #2
    Trusted Penguin Irithori's Avatar
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    Code:
    man tcpdump
    I would use it to monitor the second nic for ports, that are used by the data connections.
    You must always face the curtain with a bow.

  3. #3
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    Google and netstat.

    If the NIC's are on the same VLAN, you likely don't control which NIC is used unless you have set a specific IP to use in the application.

    For NIC's on different VLAN's, NIC selection happens by name resolution - hostname > IP > routing table > NIC selection.

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  5. #4
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    For NIC's on different VLAN's, NIC selection happens by name resolution - hostname > IP > routing table > NIC selection.
    NICs are on different VLANS.

    netstat -nr:
    Kernel IP routing table
    Destination Gateway Genmask Flags MSS Window irtt Iface
    16.131.152.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
    192.168.127.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
    0.0.0.0 16.131.152.1 0.0.0.0 UG 0 0 0 eth0

    eth0 is 100Mbps while eth1 is 1G link, does above suggest all traffic is routed through eth0??
    and thats reason I find very slow data rates, i was hoping all data will only pass through eth1 and eth0 is just for admin/GUI purposes..

  6. #5
    Trusted Penguin Irithori's Avatar
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    The default gateway is on eth0,
    so any traffic other than the net attached to eth1 (192.168.127.0/24)
    will go through eth0
    You must always face the curtain with a bow.

  7. #6
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    Agree. But is there a way to find which traffic is going to eth1 as well?
    my server from which i can administer/access GUI is also on dual port.
    is there a way for me to know which port it is using to push data and which port for web?

  8. #7
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    But is there a way to find which traffic is going to eth1 as well?
    Google and netstat - tcpdump as well.

    Re-read what Irithori posted and *understand* it. If the destination of your "data" is NOT on the network 192.168.127.0, the connection will be made using eth0.

  9. #8
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    tcpdump on eth0 can help you in analyzing tx and rx packets perinterface.

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