After switching from a wireless connection to a wired connection on a MacBook Pro laptop running Mac OS X 10.6.8, I was no longer able to access a website I needed to access to establish a VPN connection to a remote network.I had a VPN connection established before switching from the wireless to the wired network. When I plugged the network cable into the laptop for a wired connection I also changed the network settings under System Preferences on the system by selecting "Turn AirPort Off" to ensure the wireless connection would not be used. Afterwards, when I tried pinging the destination system using the wired connection, I saw the following:
$ ping vpn.example.com PING vpn.example.com (10.0.56.76): 56 data bytes ping: sendto: Network is down ping: sendto: Network is down Request timeout for icmp_seq 0 ping: sendto: Network is down Request timeout for icmp_seq 1 ping: sendto: Network is down Request timeout for icmp_seq 2 ping: sendto: Network is down Request timeout for icmp_seq 3 cping: sendto: Network is down Request timeout for icmp_seq 4 ping: sendto: Network is down Request timeout for icmp_seq 5 ping: sendto: Network is down Request timeout for icmp_seq 6 cping: sendto: Network is down Request timeout for icmp_seq 7 ping: sendto: Network is down Request timeout for icmp_seq 8 ping: sendto: Network is down Request timeout for icmp_seq 9 ^C --- vpn.example.com ping statistics --- 11 packets transmitted, 0 packets received, 100.0% packet loss
To determine why I was getting the "Network is down" message, I checked the route for the IP address associated with the destination system.
$ route get 10.0.56.76
route to: vpn.example.com
destination: vpn.example.com
gateway: 192.168.1.1
interface: en1
flags: <UP,GATEWAY,HOST,DONE,STATIC>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
0 0 3411 67 67 0 1500 0I noticed the gateway, i.e., router address, was pointing to the wireless router's IP address, 192.168.1.1, rather than the IP address for router for the wired connection, 192.168.0.1. But when I checked the default route, I saw it was correct.
$ route get default
route to: default
destination: default
mask: default
gateway: 192.168.0.1
interface: en0
flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
0 0 0 0 0 0 1500 0I flushed the routing table. Note: you must put the sudo
command before the route flush command, if you are not logged
in as root, but the account you are using is allowed to administer the
computer, and then supply your password in order to execute the
route flush command as you must be root to alter the
routing table.
$ route flush route: must be root to alter routing table $ sudo route flush default 192.168.2.1 done route: write to routing socket: No such process got only -1 for rlen
After then disconnecting the network cable from the laptop and then reconnecting it, I then saw the correct route for the webserver through the wired router, which had IP address 192.168.0.1, and was able to ping it.
$ route get 10.0.56.76
route to: vpn.example.com
destination: default
mask: default
gateway: 192.168.0.1
interface: en0
flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
0 0 0 0 0 0 1500 0
$ ping 10.0.56.76
PING 10.0.56.76 (10.0.56.76): 56 data bytes
64 bytes from 10.0.56.76: icmp_seq=0 ttl=57 time=19.955 ms
64 bytes from 10.0.56.76: icmp_seq=1 ttl=57 time=21.017 ms
^C
--- 10.0.56.76 ping statistics ---
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 19.955/20.486/21.017/0.531 msI was then also able to access the website using Safari. I had not been able to do so when I previously had tried just disconnecting and reconnecting the network cable without flushing the routing table.
