internet - Ping IP returned "destination net unreachable", even with different network

07
2014-04
  • Choon Lim

    I couldn't log in to facebook, so I ping the domain and got this:

    ping www.facebook.com

    Pinging www.facebook.com [69.171.228.14] with 32 bytes of data:

    Request timed out.

    Reply from 204.15.23.57: Destination net unreachable.

    But when I ping this IP, it is reachable.

    Pinging 204.15.23.57 with 32 bytes of data:

    Reply from 204.15.23.57: bytes=32 time=190ms TTL=51

    I realize it is something wrong with my computer, as I have tried using different networks (on the same network other devices can connect to facebook), resetting router's routing table, clear my computer arp cache...but none of it works.

    Does anyone have any idea?

    • Answers
  • r0berts

    What your commands show is the following:

    1. Your computer has resolved www.facebook.com address to be 69.171.228.14
    2. It is trying to send ping packets to it
    3. On the packet's way a router (possibly your's, at address 204.15.23.57) cannot find route to 69.171.228.14
    4. So that you know about this the router 204.15.23.57 is informing you about this with the ICMP reply message Destination net unreachable.

    In your second command you are pinging the router who gave you net unreachable reply, not facebook host, therefore unsurprisingly you get a reply from it.

    As you have helpfully pointed out - this was result from a messed-up hosts file. You also could have seen the problem if you had used nslookup to query a DNS server directly:

    nslookup
server 8.8.4.4
www.facebook.com

    This would have shown you the actual address of the facebook host and you would have noticed that it is different from the one given to you (69.171.228.14 ), so you would have known to look in the hosts file as a computer resolves IP addresses through hosts file or DNS queries.

    Having said that it is not good that a virus has been able to update the hosts file, since that should only be writable by a superuser/system (Administrator, SYSTEM or root on Linux). Therefore the implication is that the virus/trojan had high level access to the system.


    • Related Question

    windows 7 - Why can't I ping a PC on my home network?
  • AngryHacker

    Whenever I try to ping another box on my home network, it pings the wrong ip address:

    C:\Users\Papa>ping macmini
Pinging macmini.belkin [208.68.143.55] with 32 bytes of data: 
Reply from 208.68.143.55: bytes=32 time=50ms TTL=110

    As you can see it always appends belkin to anything I try to ping. So I hit up ipconfig and belkin happens to be Connection-specific DNS Suffix:

    Wireless LAN adapter Wireless Network Connection:

    Connection-specific DNS Suffix  . : belkin
IPv4 Address. . . . . . . . . . . : 192.168.2.7
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.2.1

    My setup is all DHCP, so I am not sure where belkin is coming from. I looked through all the networking stuff, as you can see below: alt text

    Bottom line: how do I fix this?


    • Related Answers
  • Matthieu Cartier

    That IP resolves to dnssearch.rr.com. Looks like a misconfiguration in that you are actually pinging a DNS search rather than using it...

    The misconfiguration is more than likely present at your router than at your computer. Try changing the DNS servers the router is using to Google DNS at 8.8.8.8 and 8.8.4.4.

  • Chau Chee Yang

    To make sure you ping to correct host, you may use 

    ping <ip-address>

    If you ping by using name (eg: macmini), it will refer to DNS service specified on your network. The DNS service will serve the request and return the IP address associated to the name you try to ping. If the DNS service doesn't return the expected IP-address, you may have to check the configuration of DNS service. This is another big topic.