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Henrik
Asked: 2011-12-17 02:39:22 +0800 CST

Can I figure out if my server has IPv4 or IPv6 from a CLI?

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Is there any method (via CLI) of knowing if the server I'm at has IPv4 or IPv6?

EDIT: As for the reason why I'm asking this question (apologies if I wasn't specific enough), I'm referring to this guide by my host (Linode).

Specifically, they say (under the section about updating /etc/hosts) that:

"If you have IPv6 enabled on your Linode, you will also want to add an entry for your IPv6 address […]".

So, I'm simply wondering if and how you can figure this out via commandline. (My OS is Ubuntu 11.10 Oneiric.)

UPDATE: Apart from ifconfig, it seems the ping6 utility might prove useful, as hinted to in this article.

command-line-interface ipv6 ipv4

3 Answers

  1. Best Answer

    It's not a "one or the other" option. You can query the network stack from the command line (see below) and this will return what IP addresses are assigned to each network interface, and you can then see from the format of these addresses which type they are.

    ipconfig for windows

    ifconfig for most *nix

    Be aware that just because an address is there, it doesn't mean that it's in use. Many modern operating systems will assign a link-local address to any active network adapter by default these days.

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  2. ifconfig will help you:

     stone@box ~ $ sudo ifconfig
 [sudo] password for stone: 
 eth1      Link encap:Ethernet  HWaddr aa:00:05:00:0a:02  
           inet addr:192.168.0.2  Bcast:192.168.0.255  Mask:255.255.255.0
           inet6 addr: fe80::a800:5ff:fe00:a02/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:8931 errors:0 dropped:0 overruns:0 frame:0
           TX packets:8250 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000 
           RX bytes:9244802 (8.8 MiB)  TX bytes:1593148 (1.5 MiB)
           Interrupt:42 Base address:0x4000

    You will see something like this, the ipv6 addr is what matters and Scope in the same line. If you see there Site then you have IPv6 routed address. (Link means only link local address.)

    • 4

  3. Your system will almost certainly have IPV4. You don't say which OS. You can use ifconfig in linux to get and look for an inet6 line 

    ifconfig | grep inet6 
inet6 addr: fe80::20c:29ff:fe5b:a5ea/64 Scope:Link

    or you can use ipconfig under windows and look for IPv6 Address in the output.

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