$ host nasa.gov
nasa.gov mail is handled by 10 ndjsnpf01.ndc.nasa.gov.
nasa.gov mail is handled by 10 ndjsnpf02.ndc.nasa.gov.
nasa.gov mail is handled by 10 ndjsnpf03.ndc.nasa.gov.
nasa.gov mail is handled by 10 ndmsnpf01.ndc.nasa.gov.
nasa.gov mail is handled by 10 ndmsnpf02.ndc.nasa.gov.
nasa.gov mail is handled by 10 ndmsnpf03.ndc.nasa.gov.
So you can send mail to username@nasa.gov
, but there is no machine nasa.gov
to connect to.
$ host www.nasa.gov
www.nasa.gov is an alias for www.nasa.gov.speedera.net.
www.nasa.gov.speedera.net is an alias for www.nasa.gov.edgesuite.net.
www.nasa.gov.edgesuite.net is an alias for a1718.x.akamai.net.
a1718.x.akamai.net has address 92.122.213.138
a1718.x.akamai.net has address 92.122.213.200
So when you ping www.nasa.gov
you are really pinging an Akamai machine via several indirections.
The NASA mail server is run by NASA directly. It doesn't reply to ping requests:
$ host ndjsnpf01.ndc.nasa.gov
ndjsnpf01.ndc.nasa.gov has address 198.117.1.121
$ whois 198.117.1.121
[...]
National Aeronautics and Space Administration NETBLK-NSI (NET-198-116-0-0-1) 198.116.0.0 - 198.123.255.255
[...]
$ ping ndjsnpf01.ndc.nasa.gov
PING ndjsnpf01.ndc.nasa.gov (198.117.1.121) 56(84) bytes of data.
3Every
ping
packet may take a different time to reach its destination and come back. This depends on the load of the hops on its way. – slhck – 2011-07-14T13:30:57.9473Ping times depend more on the route taken than load in my experience. Routers may send packets to their destination by different routes at different times. – CarlF – 2011-07-14T13:37:24.403
7Did any of you who actually picked Tom Frey's answer actually try pinging nasa.gov (minus the www) or do an NSLOOKUP? That answer is so wrong. The same firewall he says is dropping them, responds to ping www.nasa.gov. It is because it is lacking a DNS A record for NASA.gov. – KCotreau – 2011-07-14T15:35:43.453