Broadcast
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Thread: Broadcast

  1. #1
    AO French Antique News Whore
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    Broadcast

    In a normal subnet of 192.168.1.* with a subnet mask of 255.255.255.0, the broadcast address should be 192.168.1.255. I'm trying to ping my network using my this address without succes. Why?

    Where can I find a program that will brodcast a ping or a TCP Port? If you answer me Nmap, please tell the command line or a page where I can find the information! Thank.
    -Simon \"SDK\"

  2. #2
    Just a Virtualized Geek MrLinus's Avatar
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    What are the devices on the network? Generally using ping 192.168.1.255 -t (windows) or ping 192.168.1.255 -b (linux) should work unless ping is surpressed by router/switch/firewall.

    And I'm not sure what you mean by broadcasting a ping or a TCP port. No TCP port can be broadcast so to speak. If you mean broadcasting a ping to a TCP port, IIRC, ICMP is a protocol on it's own and doesn't go to a specific port.
    Goodbye, Mittens (1992-2008). My pillow will be cold without your purring beside my head
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  3. #3
    AO French Antique News Whore
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    Ping 192.168.1.255 -t doesn't work either. I get Request timed out. I'm sure that my Switch doesn't block me because I have a program that do a Broadcast and that work. I'm trying to make this program work across VPN/Subnet and I'm unable so that why I'm looking for a utilites to do the same to locate the problem. The first step is to be find that program and make it work since my own subnet.
    -Simon \"SDK\"

  4. #4
    Just a Virtualized Geek MrLinus's Avatar
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    Have you run arp -a after the ping broadcast just to see if anything is actually being picked up after the fact? What kind of VPN is it? If it's a router-to-router setup, is it possible that one is blocking it? (my gut says something is blocking). Have you done a sniff of the network to see what/where packets are going and other activity that might be going on?
    Goodbye, Mittens (1992-2008). My pillow will be cold without your purring beside my head
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  5. #5
    AO French Antique News Whore
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    I'm pretty sure the VPN is blocking the broadcast. But I'm also sure that the broadcast is NOT block in my local subnet. Right now, I only want to be able to broadcast a ping or an UDP port inside my local subnet. After I'm able to do that, I'll attack myself to get the broadcast work across the VPN.
    -Simon \"SDK\"

  6. #6
    Just Another Geek
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    192.168.1.255 is a subnet broadcast. 255.255.255.255 is a broadcast address.

    What OSs are there on that subnet? If it consists of windows only machines you'll never get a response. A Windows machine will not respond to a broadcast ping (by default). A linux machine may respond depending on the configuration (read: distro). Both have the option to turn it on or off.

    Please note: You should make sure it's turned off. If it's turned on your network is vulnerable to a smurf attack.

    As for nmap, try nmap -sP -vv -n 192.168.1.255

    Originally posted here by MsMittens
    No TCP port can be broadcast so to speak.
    Try and send a SYN packet to 192.168.1.255/port 80 i.e. and see what happens..not sure what should though..

    nmap -sS -vv -n -p80 -P0 192.168.1.255 should do the trick.
    Oliver's Law:
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  7. #7
    AO French Antique News Whore
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    Can I broadcast over a UDP port? Will I get answer from service listening over that port?

    I try doing a nmap -sU -p***** -v -P0 255.255.255.255
    Starting nmap 3.75 ( http://www.insecure.org/nmap ) at 2004-11-04 10:31 Eastern
    Standard Time
    Initiating UDP Scan against 255.255.255.255 [1 port] at 10:31
    The UDP Scan took 2.06s to scan 1 total ports.
    Host 255.255.255.255 appears to be up ... good.
    Interesting ports on 255.255.255.255:
    PORT STATE SERVICE
    *****/udp open|filtered unknown

    Nmap run completed -- 1 IP address (1 host up) scanned in 2.235 seconds
    -Simon \"SDK\"

  8. #8
    Just a Virtualized Geek MrLinus's Avatar
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    nmap -sS -vv -n -p80 -P0 192.168.1.255
    I would have thought that it would have been more like nmap -sS -vv -n -p80 -P0 192.168.1.0/24 sent out over the network rather than the broadcast to get all hosts to respond to a probe of port 80.

    Perhaps someone should get TH13's opinion?
    Goodbye, Mittens (1992-2008). My pillow will be cold without your purring beside my head
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  9. #9
    Just Another Geek
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    If there's something listening, it's highly probably that it'll respond.
    It might be a good idea to keep a sniffer running when doing these scans.
    It'll give you more detailed information on what's happening.

    nmap -sS -vv -n -p80 -P0 192.168.1.0/24
    That would scan all addresses in the 192.168.1.0-192.168.1.255 range.
    It would be the same as using 192.168.1.*

    Oliver's Law:
    Experience is something you don't get until just after you need it.

  10. #10
    AO French Antique News Whore
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    I try those command and both work

    nmap -sU -p42508 -P0 -S 192.168.1.18 -vv 192.168.1.1-10

    nmap -sU -p42508 -P0 -S 192.168.1.18 -vv 192.168.2.50-65

    Does I need the answer to this question : Can I broadcast over a UDP port? If yes, how?

    What I find stranage also is doing a nmap -sU -p42508 -P0 -S 192.168.1.18 -vv 255.255.255.255 only return me one host. This, I don't understand at all.
    -Simon \"SDK\"

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