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Add recipe for 8.8.8.8
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mvp
mvp
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Many corporate firewalls block ICMP - which is the protocol is used by ping utility.

Better solution for this is to try TCP connection to google.com:80.

Easiest way to check for basic internet connectivity in shell script is utility nc (it should be easily available on most Linux systems):

nc -w 3 -z google.com 80
echo $?

This means check if port 80 on google.com is open, and timeout after 3 seconds. If connection was successful, it will print 0, and if it failed, it will print 1.

If you want to check internet connectivity without checking DNS (which could be broken in itself), you can use Google's preferred DNS server 8.8.8.8, but the only port that it has open is 53 (aka domain):

nc -w 3 -z 8.8.8.8 53
echo $?

However, port 53 can be also blocked by your corporate firewall (not common, but possible). Ports 80 and 443, on other hand, are almost never firewalled.

Many corporate firewalls block ICMP - which is the protocol is used by ping utility.

Better solution for this is to try TCP connection to google.com:80.

Easiest way to check for basic internet connectivity in shell script is utility nc (it should be easily available on most Linux systems):

nc -w 3 -z google.com 80
echo $?

This means check if port 80 on google.com is open, and timeout after 3 seconds. If connection was successful, it will print 0, and if it failed, it will print 1.

Many corporate firewalls block ICMP - which is the protocol is used by ping utility.

Better solution for this is to try TCP connection to google.com:80.

Easiest way to check for basic internet connectivity in shell script is utility nc (it should be easily available on most Linux systems):

nc -w 3 -z google.com 80
echo $?

This means check if port 80 on google.com is open, and timeout after 3 seconds. If connection was successful, it will print 0, and if it failed, it will print 1.

If you want to check internet connectivity without checking DNS (which could be broken in itself), you can use Google's preferred DNS server 8.8.8.8, but the only port that it has open is 53 (aka domain):

nc -w 3 -z 8.8.8.8 53
echo $?

However, port 53 can be also blocked by your corporate firewall (not common, but possible). Ports 80 and 443, on other hand, are almost never firewalled.

Source Link
mvp
mvp
  • 4.4k
  • 23
  • 27

Many corporate firewalls block ICMP - which is the protocol is used by ping utility.

Better solution for this is to try TCP connection to google.com:80.

Easiest way to check for basic internet connectivity in shell script is utility nc (it should be easily available on most Linux systems):

nc -w 3 -z google.com 80
echo $?

This means check if port 80 on google.com is open, and timeout after 3 seconds. If connection was successful, it will print 0, and if it failed, it will print 1.