SPUG: I must be missing something with Net::Ping

Alyssa Harding alyssa at atuin.net
Mon Oct 8 19:07:03 CDT 2001

Hi List,

Maybe someone else can look at this and tell me I'm missing something 

I've got a script which runs on a server outside the firewall and pings 
certain servers.  i'm using Net::Ping to do the pinging but I'm coming 
up with wierd results.

use Net::Ping;

my $isp = '<ip address of isp router>';
my $outside='www.yahoo.com';

my $p = Net::Ping->new();  # by default uses icmp protocol

if($p->ping($isp)) {
  print "isp reached\n";
} else {
  print "isp not reached\n";

if( $p->ping($outside)) {
  print "outside reached\n";
} else {
  print "outside not reached\n";


When I run the script I get the following output:
isp reached
outside not reached

In other words, I can ping our ISP's router but I can't ping yahoo.com.
So I tried on the command line (HPUX v10.20 seems to have the same ping 
as my Red Hat 7.1 box with different option flags - they are 
functionally the same though):
ping <isp's router>
and got a response just fine - good.  I expected that. So I tried:
ping www.yahoo.com
and got a response just fine - hmmmm.  

Why won't the script do what the command line does when they are both 
using the same protocol to do the same thing?  Traceroute shows the 
first hop being to the ISP's router and then about 18 more hops and #20 
is yahoo.

Any ideas?

Alyssa Harding
"Why's it called Ming?" said the Archchancellor, on cue.
The Bursar tapped the pot. It went *ming*.
        -- Discworld archeology revealed
           (Terry Pratchett, Moving Pictures)

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