IPv6 versus IPv4

Addresses are much larger: 4 bytes are now 16 (32 bits to 128 bits).
IPv6 and IPv4 are philosophically somewhat dissimilar
IPv6 addresses are usually issued in large blocks (which might make for some interesting practices, having lots of ip numbers!)
Nice reference page at IPv6VE.

ping6

root@(none):~# ip -6 addr show
1: lo:  mtu 65536 
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0:  mtu 1500 qlen 1000
    inet6 2600:3c00::f03c:91ff:fe33:a3/64 scope global dynamic 
       valid_lft 2591993sec preferred_lft 604793sec
    inet6 fe80::f03c:91ff:fe33:a3/64 scope link 
       valid_lft forever preferred_lft forever
root@(none):~# ping6 www.google.com
PING www.google.com(lax17s01-in-x12.1e100.net) 56 data bytes
64 bytes from lax17s01-in-x12.1e100.net: icmp_seq=1 ttl=49 time=44.7 ms
64 bytes from lax17s01-in-x12.1e100.net: icmp_seq=2 ttl=49 time=44.0 ms
64 bytes from lax17s01-in-x12.1e100.net: icmp_seq=3 ttl=49 time=43.4 ms
64 bytes from lax17s01-in-x12.1e100.net: icmp_seq=4 ttl=49 time=44.2 ms
64 bytes from lax17s01-in-x12.1e100.net: icmp_seq=5 ttl=49 time=44.0 ms

Let's add another active address

root@(none):~# ip -6 addr show
1: lo:  mtu 65536 
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0:  mtu 1500 qlen 1000
    inet6 2600:3c00::f03c:91ff:fe33:a3/64 scope global dynamic 
       valid_lft 2591993sec preferred_lft 604793sec
    inet6 fe80::f03c:91ff:fe33:a3/64 scope link 
       valid_lft forever preferred_lft forever
root@(none):/tmp# ifconfig eth0 inet6 add 2600:3c00::f03c:91ff:fe33:a4/64
root@(none):/tmp# ip -6 addr show
1: lo:  mtu 65536 
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
3: eth0:  mtu 1500 qlen 1000
    inet6 2600:3c00::f03c:91ff:fe33:a4/64 scope global 
       valid_lft forever preferred_lft forever
    inet6 2600:3c00::f03c:91ff:fe33:a3/64 scope global dynamic 
       valid_lft 2591999sec preferred_lft 604799sec
    inet6 fe80::f03c:91ff:fe33:a3/64 scope link 
       valid_lft forever preferred_lft forever

Or using the older ifconfig program

root@(none):/tmp# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr f2:3c:91:33:00:a3  
          inet addr:45.56.74.139  Bcast:45.56.74.255  Mask:255.255.255.0
          inet6 addr: 2600:3c00::f03c:91ff:fe33:a4/64 Scope:Global
          inet6 addr: 2600:3c00::f03c:91ff:fe33:a3/64 Scope:Global
          inet6 addr: fe80::f03c:91ff:fe33:a3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:4886623 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5131711 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:621051732 (592.2 MiB)  TX bytes:880096269 (839.3 MiB)

IPv6 and DNS

DNS A records assume that you are using a 4 byte address, so a new record type, the AAAA ("quad A") record type was created to handle IPv6:

root@(none):~# dig AAAA www.google.com

; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> AAAA www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 10531
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
		;www.google.com.INAAAA

;; ANSWER SECTION:
		www.google.com.143INAAAA2a00:1450:4010:c01::68

;; Query time: 1 msec
;; SERVER: 72.14.188.5#53(72.14.188.5)
;; WHEN: Wed Oct 21 18:55:35 2015
;; MSG SIZE  rcvd: 60

IPv6 in action

Here's a wget using IPv6:

         
root@(none):/tmp# wget -6 http://www.google.com/index.html
--2015-10-21 18:57:16--  http://www.google.com/index.html
Resolving www.google.com (www.google.com)... 2607:f8b0:4007:802::1011
Connecting to www.google.com (www.google.com)|2607:f8b0:4007:802::1011|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: `index.html'



2015-10-21 18:57:16 (443 KB/s) - `index.html' saved [18818]