eth0:1 and nmap?

Discussion in 'Linux Networking' started by iksrazal, May 18, 2004.

  1. iksrazal

    iksrazal Guest

    I'm trying to troubleshoot a network, and ifconfig gave me a response
    I've never seen:


    eth0 Link encap:Ethernet HWaddr 00:01:03:34:6C:B4
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:34648 errors:0 dropped:0 overruns:1 frame:0
    TX packets:21424 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:3085669 (2.9 Mb) TX bytes:3113240 (2.9 Mb)
    Interrupt:10 Base address:0xec00

    eth0:1 Link encap:Ethernet HWaddr 00:01:03:34:6C:B4
    inet addr:192.168.238.60 Bcast:192.168.238.255
    Mask:255.255.255.0
    UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
    RX packets:34648 errors:0 dropped:0 overruns:1 frame:0
    TX packets:21426 errors:0 dropped:0 overruns:0 carrier:0
    collisions:0 txqueuelen:100
    RX bytes:3085669 (2.9 Mb) TX bytes:3113572 (2.9 Mb)
    Interrupt:10 Base address:0xec00


    1) What does eth0:1 mean? Could it be ip aliasing? I'm running RH9 - a
    stock kernel I believe, which I don't think has ip aliasing support
    because its deprecated, but I'm not sure.

    2) How can I fix nmap in this case:
    /usr/local> nmap -p 389 192.168.238.61

    Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
    Failed to lookup device subnet/netmask: eth0: no IPv4 address assigned
    QUITTING!

    /usr/local> nmap -e eth0:1 -p 389 192.168.238.61

    Starting nmap V. 3.00 ( www.insecure.org/nmap/ )
    I cannot figure out what source address to use for device eth0:1, does
    it even exist?
    QUITTING!

    iksrazal
     
    iksrazal, May 18, 2004
    #1
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  2. iksrazal

    Cameron Kerr Guest

    It certainly does. Under IPv4, each interface can have only one address
    attached to it. (IPv6 doesn't have this limitation). To get around this,
    we make virtual interfaces, giving each one its own seperate address.
    You must assign eth0 an interface if you want to use it meaningfully,
    otherwise the packets won't have a valid source address.
    This is a bug. Report it.

    You can work around it by telling nmap which source address to bind to,
    by using the -S option.
     
    Cameron Kerr, May 19, 2004
    #2
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  3. IP aliasing is not depreciated. What may be depreciated is having to add
    it to the kernel, because I believe it is native now (always there). Why
    are you using an alias without assigning an IP to eth0?
    You might try -S which is just before -e in 'man nmap'.
     
    David Efflandt, May 26, 2004
    #3
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