How to get all arp entries for a certain network

Discussion in 'Linux Networking' started by Zahi Shahak, Sep 2, 2004.

  1. Zahi Shahak

    Zahi Shahak Guest

    How can I get my arp table to fill up with all the objects in a
    certain network(which I have the network/netmask). The only way I
    found is pinging all the objects in the network one by one....I know
    there's a better way. Using redhat , perl solutions are welcome !
    10x in advance
    Zahi Shahak, Sep 2, 2004
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    Hash: SHA1
    NotDashEscaped: You need GnuPG to verify this message

    man ping

    Michael Heiming (GPG-Key ID: 0xEDD27B94)
    mail: echo | perl -pe 'y/a-z/n-za-m/'
    Version: GnuPG v1.2.4 (GNU/Linux)

    -----END PGP SIGNATURE-----
    Michael Heiming, Sep 2, 2004
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  3. Zahi Shahak

    James Knott Guest

    You can do a broadcast ping, to the broadcast address.
    James Knott, Sep 2, 2004
  4. Zahi Shahak

    Moe Trin Guest

    Ping the broadcast (ping -b), but don't do this very much, as it can
    generate a lot of traffic. And remember:

    1. Some hosts will not respond to a broadcast ping, though they _will_
    respond to a unicast ping (to their speciifc address).

    2. Some hosts have firewalls configured to block/ignore pings.

    A less invasive technique is to just run a sniffer like tcpdump
    looking for ARP request/reply packets. I used to run an application
    that monitored the ARP cache of the routers and DNS servers (then
    comparing the results with a data base to detect "unusual" events)
    for security purposes. 'arpwatch' is somewhat similar in function.

    Old guy
    Moe Trin, Sep 3, 2004
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