nmap from net a to net B, don't work, but ping yes - Networking

This is a discussion on nmap from net a to net B, don't work, but ping yes - Networking ; I have 4 pc pc1 10.10.10.100 pc2 10.10.1.101 pc3 10.10.1.102 pc4 10.10.1.103 pc2 have this routing table: 10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 ...

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Thread: nmap from net a to net B, don't work, but ping yes

  1. nmap from net a to net B, don't work, but ping yes

    I have 4 pc

    pc1 10.10.10.100
    pc2 10.10.1.101
    pc3 10.10.1.102
    pc4 10.10.1.103

    pc2 have this routing table:
    10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
    10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
    0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth1

    it'is a router between 10.10.1.0/24 and 10.10.10.0/24
    i do in pc2: sysctl -w net.ipv4.ip_forward=1

    when i ping from pc1 to pc3 it works fine

    but if i do from pc1 to 10.10.1.0/24
    nmap -sS -A 10.10.1.0/24

    it find only pc2 (router) because it have eth1 in the same network of pc1

    in the same time if i do from pc2:
    tcpdump -n -i eth0
    it don't capture nothing

    but
    tcpdump -n -i eth1
    capture the traffic

    why this behavior?

    thanks a lot and scuse me for my bad english

    --
    Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
    sul http://www.iltermitano.it/)

    A computer is like an air conditioner,
    it stops working when you open Windows.
    Registered Linux user #457776

  2. Re: nmap from net a to net B, don't work, but ping yes

    RicK_Murphy wrote:
    > I have 4 pc


    > pc1 10.10.10.100
    > pc2 10.10.1.101


    What's pc2's other IP address (on the 10.10.10.0/24 network)?


    > pc3 10.10.1.102
    > pc4 10.10.1.103


    > pc2 have this routing table:
    > 10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
    > 10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
    > 0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth1


    > it'is a router between 10.10.1.0/24 and 10.10.10.0/24
    > i do in pc2: sysctl -w net.ipv4.ip_forward=1


    > when i ping from pc1 to pc3 it works fine


    > but if i do from pc1 to 10.10.1.0/24
    > nmap -sS -A 10.10.1.0/24


    > it find only pc2 (router) because it have eth1 in the same network of pc1


    What are the routing tables on pc1, pc3, and pc4? It looks like you may
    have forgotten routes to pc2 for the "other" network.

    Chris

  3. Re: nmap from net a to net B, don't work, but ping yes

    Chris Davies wrote:

    > RicK_Murphy
    >


    > wrote:
    >> I have 4 pc

    >
    >> pc1 10.10.10.100
    >> pc2 10.10.1.101

    >
    > What's pc2's other IP address (on the 10.10.10.0/24 network)?


    eth1 of pc2: 10.10.10.101


    >> pc3 10.10.1.102
    >> pc4 10.10.1.103

    >
    >> pc2 have this routing table:
    >> 10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0
    >> eth0
    >> 10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0
    >> eth1
    >> 0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0
    >> eth1

    >
    >> it'is a router between 10.10.1.0/24 and 10.10.10.0/24
    >> i do in pc2: sysctl -w net.ipv4.ip_forward=1

    >
    >> when i ping from pc1 to pc3 it works fine

    >
    >> but if i do from pc1 to 10.10.1.0/24
    >> nmap -sS -A 10.10.1.0/24

    >
    >> it find only pc2 (router) because it have eth1 in the same network of pc1

    >
    > What are the routing tables on pc1, pc3, and pc4? It looks like you may
    > have forgotten routes to pc2 for the "other" network.


    in pc1:
    10.10.1.0 10.10.10.101 255.255.255.0 UG 0 0 0 eth1
    10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1
    0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth1

    in pc3, pc4:
    10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
    0.0.0.0 10.10.1.101 0.0.0.0 UG 0 0 0 eth0

    observe that ping works fine

    >
    > Chris

    thanks
    --
    Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
    sul http://www.iltermitano.it/)

    A computer is like an air conditioner,
    it stops working when you open Windows.
    Registered Linux user #457776

  4. Re: nmap from net a to net B, don't work, but ping yes

    Hi. I find that, sometimes, ping lies. Are you, for example, able to
    actually ssh from pc1 to pc3? I'm guessing no. That being said, I'd
    be interested in knowing what the routing tables on pc2, and pc3 are;
    do you have 10.10.1.101 as their default gateway? And how about pc1?
    You don't state what the IP address for eth1 on pc2 is, but that had
    better be the default gateway on pc1 or else things won't work right.
    So, to summarize:
    1) What are your routing tables on pc1, pc3 and pc4?
    2) What is eth1's IP address on pc2?

    -Ken

    On Sep 24, 6:26*am, RicK_Murphy

    wrote:
    > I have 4 pc
    >
    > pc1 10.10.10.100
    > pc2 10.10.1.101
    > pc3 10.10.1.102
    > pc4 10.10.1.103
    >
    > pc2 have this routing table:
    > 10.10.1.0 * * * 0.0.0.0 * * * * 255.255.255.0 * U * *0 * * *0 * * * *0 eth0
    > 10.10.10.0 * * *0.0.0.0 * * * * 255.255.255.0 * U * *0 * * *0 * * * *0 eth1
    > 0.0.0.0 * * * * 10.10.10.1 * * *0.0.0.0 * * * * UG * *0 * * *0 * * * *0 eth1
    >
    > it'is a router between 10.10.1.0/24 and 10.10.10.0/24
    > i do in pc2: sysctl -w net.ipv4.ip_forward=1
    >
    > when i ping from pc1 to pc3 it works fine
    >
    > but if i do from pc1 to 10.10.1.0/24
    > *nmap -sS -A 10.10.1.0/24
    >
    > it find only pc2 (router) because it have eth1 in the same network of pc1
    >
    > in the same time if i do from pc2:
    > tcpdump -n -i eth0
    > it don't capture nothing
    >
    > but
    > tcpdump -n -i eth1
    > capture the traffic
    >
    > why this behavior?
    >
    > thanks a lot and scuse me for my bad english
    >
    > --
    > Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
    > sulhttp://www.iltermitano.it/)
    >
    > A computer is like an air conditioner,
    > it stops working when you open Windows.
    > Registered Linux user #457776



  5. Re: nmap from net a to net B, don't work, but ping yes

    Ravenpi wrote:

    > Hi. I find that, sometimes, ping lies. Are you, for example, able to
    > actually ssh from pc1 to pc3? I'm guessing no.


    I tryed
    ssh root@10.10.1.103
    it's work fine

    > 1) What are your routing tables on pc1, pc3 and pc4?


    in pc1:
    10.10.1.0 * * * 10.10.10.101 * *255.255.255.0 * UG * *0 * * *0 * * * *0 eth1
    10.0.0.0 * * * *0.0.0.0 * * * * 255.0.0.0 * * * U * * 0 * * *0 * * * *0 eth1
    0.0.0.0 * * * * 10.10.10.1 * * *0.0.0.0 * * * * UG * *0 * * *0 * * * *0 eth1

    in pc3, pc4:
    10.10.1.0 * * * 0.0.0.0 * * * * 255.255.255.0 * U * * 0 * * *0 * * * *0 eth0
    0.0.0.0 * * * * 10.10.1.101 * * 0.0.0.0 * * * * UG * *0 * * *0 * * * *0 eth0

    > 2) What is eth1's IP address on pc2?


    10.10.10.101


    --
    Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
    sul http://www.iltermitano.it/)

    A computer is like an air conditioner,
    it stops working when you open Windows.
    Registered Linux user #457776

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