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Full Discussion: ping blocking
Special Forums IP Networking ping blocking Post 302531666 by programAngel on Friday 17th of June 2011 12:06:38 PM
Old 06-17-2011
Quote:
Originally Posted by Corona688
If you can get it, the arping utility is useful for telling between obnoxious firewalls and actual network problems. A client can't ignore ARP and still communicate over IP, afterall.

[edit] It of course only can send arp over a local subnet, though.

Some distributions of linux do block ping. Can your client ping you? If so it's not likely to be blocked since they're the same distro.

If your client is behind NAT you may not be able to directly ping it from the host.
the network setting of the VM is bridge so they are not behind NAT.

When I do ping to the VM from the command line it is working as well as from the other direction (from the VM to the host OS(of the guest VM)).

However the nmap can not find any host behind the IP.
I get the following message :
Code:
Starting Nmap 5.21 ( http://nmap.org ) at 2011-06-17 18:58 IDT
Note: Host seems down. If it is really up, but blocking our ping probes, try -PN
Nmap done: 1 IP address (0 hosts up) scanned in 0.04 seconds

---------- Post updated at 07:05 PM ---------- Previous update was at 06:59 PM ----------

---------- Post updated at 07:06 PM ---------- Previous update was at 07:05 PM ----------

Quote:
Originally Posted by Corona688
Repeating the same questions doesn't us the information we need to help you.
Thank you.


what is the information you need for helping me?

I basically run ubuntu as the OS of my computer.
I have installed virtual box and created two VM.
Both scientific linux, one was installed as a web server and the other was installed as a developing station.

In the VM network setting I give both of them bridge.

And when I do ifconfig both show legal internal IP address just link my host OS (ubuntu).
All of the the host OS and the two guest OS have the same three first octet of the IP address.

I can do ping from and to the guest OS as well as the host OS.

However nmap claim that there is no host behind the IP of the guest OS or that something blocking ping.

However this is weird because I am able to do ping to the guest OS.

due you need any more information?

What do you think can make this problem?
 

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ping(8) 						      System Manager's Manual							   ping(8)

Name
       ping - send ICMP ECHO_REQUEST packets to network hosts

Syntax
       /etc/ping [ options ] host [ datasize [ npackets ]]

Description
       The  DARPA  Internet  is  a large and complex network of hardware connected together by gateways.  The command utilizes the ICMP protocol's
       mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from a host or gateway.	ECHO_REQUEST datagrams (pings) have an IP and ICMP
       header,	followed  by  a  struct timeval, and then an arbitrary number of pad bytes used to fill out the packet.  The length of the default
       datagram 64 bytes, but this may be changed using the command-line option.

       Typing ``ping host'' without any options will either report ``host is alive'' or ``no answer from host''.  To get more statistics  use  the
       -l option or one of the other options.

       When  using  for  fault	isolation,  it should first be run on the local host to verify that the local network interface is up and running.
       Then, hosts and gateways further and further away should be pinged.  The command with options sends one datagram per second and prints  one
       line  of  output  for every ECHO_RESPONSE returned.  No output is produced if there is no response.  If an optional npackets is given, only
       that number of requests is sent.  Round-trip times and packet loss statistics are computed.  When all responses have been received  or  the
       program times out with npackets specified, or if the program is terminated with a SIGINT, a brief summary is displayed.

Options
       -d   Turns on SO_DEBUG flag on the socket.

       -l   Gives more statistics than if is used without options.  Long output.

       -r   Bypasses  the  normal  routing  tables and sends directly to a host on an attached network.  If the host is not on a directly-attached
	    network, an error is returned.  This option can be used to ping a local host through an interface that has no route through  it.   For
	    example, after the interface was dropped by

       -v   Lists ICMP packets other than ECHO RESPONSE that are received. Verbose output.

Restrictions
       This  program is intended for use in network testing, measurement, and management.  It should be used primarily for manual fault isolation.
       Because of the load it could impose on the network, it is unwise to use during normal operations or from automated scripts.

See Also
       netstat(1), ifconfig(8c)

																	   ping(8)
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