In this blog, we will see the subnet size of IPv6, and also we will see some of the other information about IPv6 in this lesson. Let’s go ahead.
IPv6 requires an IPv6-enabled network. IPv6 connectivity delivered directly by an ISP is ideal. Some ISPs deploy a dual stack configuration in which IPv4 and IPv6 are delivered simultaneously on the same transport. Other ISPs use tunneling or deployment types to provide IPv6 indirectly. It is also possible to use a third party provider such as Hurricane Electric’s tunnelbroker service
Some mobile operating systems have varying levels of support for IPv6. Android and iOS both support IPv6, but Android only has support for stateless auto configuration for obtaining an IP address on Wi-Fi and not DHCPv6. IPv6 is part of the LTE specifications so any mobile device supporting LTE networks supports IPv6 as well.
IPv6 Subnet Size Reference Table:
| IPv6 CIDR Subnet | Number of IPs |
| /128 | 1 |
| /127 | 2 |
| /126 | 4 |
| /125 | 8 |
| /124 | 16 |
| /123 | 32 |
| /122 | 64 |
| /121 | 128 |
| /120 | 256 |
| /119 | 512 |
| /118 | 1,024 |
| /117 | 2,048 |
| /116 | 4,096 |
| /115 | 8,192 |
| /114 | 16,384 |
| /113 | 32,768 |
| /112 | 65,536 |
| /111 | 131,072 |
| /110 | 262,144 |
| /109 | 524,288 |
| /108 | 1,048,576 |
| /107 | 2,097,152 |
| /106 | 4,194,304 |
| /105 | 8,388,608 |
| /104 | 16,777,216 |
| /103 | 33,554,432 |
| /102 | 67,108,864 |
| /101 | 134,217,728 |
| /100 | 268,435,456 |
| /99 | 536,870,912 |
| /98 | 1,073,741,824 |
| /97 | 2,147,483,648 |
| /96 | 4,294,967,296 |
| /95 | 8,589,934,592 |
| /94 | 17,179,869,184 |
| /93 | 34,359,738,368 |
| /92 | 68,719,476,736 |
| /91 | 137,438,953,472 |
| /90 | 274,877,906,944 |
| /89 | 549,755,813,888 |
| /88 | 1,099,511,627,776 |
| /87 | 2,199,023,255,552 |
| /86 | 4,398,046,511,104 |
| /85 | 8,796,093,022,208 |
| /84 | 17,592,186,044,416 |
| /83 | 35,184,372,088,832 |
| /82 | 70,368,744,177,664 |
| /81 | 140,737,488,355,328 |
| /80 | 281,474,976,710,656 |
| /79 | 562,949,953,421,312 |
| /78 | 1,125,899,906,842,624 |
| /77 | 2,251,799,813,685,248 |
| /76 | 4,503,599,627,370,496 |
| /75 | 9,007,199,254,740,992 |
| /74 | 18,014,398,509,481,985 |
| /73 | 36,028,797,018,963,968 |
| /72 | 72,057,594,037,927,936 |
| /71 | 144,115,188,075,855,872 |
| /70 | 288,230,376,151,711,744 |
| /69 | 576,460,752,303,423,488 |
| /68 | 1,152,921,504,606,846,976 |
| /67 | 2,305,843,009,213,693,952 |
| /66 | 4,611,686,018,427,387,904 |
| /65 | 9,223,372,036,854,775,808 |
| Residential – /64 | 18,446,744,073,709,551,616 |
| /63 | 36,893,488,147,419,103,232 |
| /62 | 73,786,976,294,838,206,464 |
| /61 | 147,573,952,589,676,412,928 |
| /60 | 295,147,905,179,352,825,856 |
| /59 | 590,295,810,358,705,651,712 |
| /58 | 1,180,591,620,717,411,303,424 |
| /57 | 2,361,183,241,434,822,606,848 |
| /56 | 4,722,366,482,869,645,213,696 |
| /55 | 9,444,732,965,739,290,427,392 |
| /54 | 18,889,465,931,478,580,854,784 |
| /53 | 37,778,931,862,957,161,709,568 |
| /52 | 75,557,863,725,914,323,419,136 |
| /51 | 151,115,727,451,828,646,838,272 |
| /50 | 302,231,454,903,657,293,676,544 |
| /49 | 604,462,909,807,314,587,353,088 |
| Business – /48 | 1,208,925,819,614,629,174,706,176 |
| /47 | 2,417,851,639,229,258,349,412,352 |
| /46 | 4,835,703,278,458,516,698,824,704 |
| /45 | 9,671,406,556,917,033,397,649,408 |
| /44 | 19,342,813,113,834,066,795,298,816 |
| /43 | 38,685,626,227,668,133,590,597,632 |
| /42 | 77,371,252,455,336,267,181,195,264 |
| /41 | 154,742,504,910,672,534,362,390,528 |
| /40 | 309,485,009,821,345,068,724,781,056 |
| /39 | 618,970,019,642,690,137,449,562,112 |
| /38 | 1,237,940,039,285,380,274,899,124,224 |
| /37 | 2,475,880,078,570,760,549,798,248,448 |
| /36 | 4,951,760,157,141,521,099,596,496,896 |
| /35 | 9,903,520,314,283,042,199,192,993,792 |
| /34 | 19,807,040,628,566,084,398,385,987,584 |
| /33 | 39,614,081,257,132,168,796,771,975,168 |
| ISP – /32 | 79,228,162,514,264,337,593,543,950,336 |
| /31 | 158,456,325,028,528,675,187,087,900,672 |
| /30 | 316,912,650,057,057,350,374,175,801,344 |
| /29 | 633,825,300,114,114,700,748,351,602,688 |
| /28 | 1,267,650,600,228,229,401,496,703,205,376 |
| /27 | 2,535,301,200,456,458,802,993,406,410,752 |
| /26 | 5,070,602,400,912,917,605,986,812,821,504 |
| /25 | 10,141,204,801,825,835,211,973,625,643,008 |
| /24 | 20,282,409,603,651,670,423,947,251,286,016 |
| /23 | 40,564,819,207,303,340,847,894,502,572,032 |
| /22 | 81,129,638,414,606,681,695,789,005,144,064 |
| /21 | 162,259,276,829,213,363,391,578,010,288,128 |
| /20 | 324,518,553,658,426,726,783,156,020,576,256 |
| /19 | 649,037,107,316,853,453,566,312,041,152,512 |
| /18 | 1,298,074,214,633,706,907,132,624,082,305,024 |
| /17 | 2,596,148,429,267,413,814,265,248,164,610,048 |
| /16 | 5,192,296,858,534,827,628,530,496,329,220,096 |
| /15 | 10,384,593,717,069,655,257,060,992,658,440,192 |
| /14 | 20,769,187,434,139,310,514,121,985,316,880,384 |
| /13 | 41,538,374,868,278,621,028,243,970,633,760,768 |
| /12 | 83,076,749,736,557,242,056,487,941,267,521,536 |
| /11 | 166,153,499,473,114,484,112,975,882,535,043,072 |
| /10 | 332,306,998,946,228,968,225,951,765,070,086,144 |
| /9 | 664,613,997,892,457,936,451,903,530,140,172,288 |
| /8 | 1,329,227,995,784,915,872,903,807,060,280,344,576 |
IPv6 Subnet Reference Prefix Lengths:
2402:9400:0000:0000:0000:0000:0000:0001
XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX
||| |||| |||| |||| |||| |||| ||||
||| |||| |||| |||| |||| |||| |||128
||| |||| |||| |||| |||| |||| ||124
||| |||| |||| |||| |||| |||| |120
||| |||| |||| |||| |||| |||| 116
||| |||| |||| |||| |||| |||112
||| |||| |||| |||| |||| ||108
||| |||| |||| |||| |||| |104
||| |||| |||| |||| |||| 100
||| |||| |||| |||| |||96
||| |||| |||| |||| ||92
||| |||| |||| |||| |88
||| |||| |||| |||| 84
||| |||| |||| |||80
||| |||| |||| ||76
||| |||| |||| |72
||| |||| |||| 68
||| |||| |||64
||| |||| ||60
||| |||| |56
||| |||| 52
||| |||48
||| ||44
||| |40
||| 36
||32
|28
24
Note: The IP address above is an IP address allocated to Crucial Paradigm.
Example of /64 Allocations:
/64 IPv6 allocations are usually given to end users, who do not require any VLANs. It allows auto-configuration, or SLAAC so makes life a lot easier when configuring.
A /64 is a standard size IPv6 subnet as defined by the IETF. It is smallest subnet that can used locally if auto-configuration is desired.
Typically, an ISP assigns a /64 or smaller subnet to establish service on the WAN. An additional network is routed for LAN use. The size of the allocation depends upon the ISP, but it’s not uncommon to see end users receive at least a /64 and even up to a /48.
A tunnel service provider such as tunnelbroker.net run by Hurricane Electric will allocate a /48 in addition to a routed /64 subnet and a /64 interconnect.
Assignments larger than /64 usually adopt the first /64 for LAN and subdivide the rest for requirements such as VPN tunnel, DMZ, or a guest network.
It is fairly easy to calculate /64 allocations, and a subnet calculator is not required. In fact this is the case with assigning IPv6 allocations, it can be done fairly easily without any calculator (I’ll demonstrate this later in the reference sheet):
2402:9400:1000:0::/64
2402:9400:1000:1::/64
2402:9400:1000:2::/64
2402:9400:1000:3::/64
2402:9400:1000:4::/64
2402:9400:1000:5::/64
2402:9400:1000:6::/64
2402:9400:1000:7::/64
2402:9400:1000:8::/64
2402:9400:1000:9::/64
2402:9400:1000:a::/64
2402:9400:1000:b::/64
2402:9400:1000:c::/64
2402:9400:1000:e::/64
2402:9400:1000:e::/64
2402:9400:1000:f::/64
2402:9400:1000:10::/64
2402:9400:1000:11::/64
Example of /48 Allocations:
/48 allocations are usually provided to business, who require additional VLANs or may require the range to be split up. Using a /48 allocation would allow them to do so.
2402:9400:10::/48
2402:9400:11::/48
2402:9400:12::/48
2402:9400:13::/48
2402:9400:14::/48
2402:9400:15::/48
2402:9400:16::/48
2402:9400:17::/48
2402:9400:18::/48
2402:9400:19::/48
2402:9400:1a::/48
2402:9400:1b::/48
2402:9400:1c::/48
2402:9400:1e::/48
2402:9400:1f::/48
2402:9400:20::/48
IPv6 Subnet Calculator NOT REQUIRED!
In most cases a subnet calculator will not be required, since IPv6 using hex (hexadecimal) – and so long as the prefix length is a multiple of 4, it makes it quite easy. For example (this is also where the table “IPv6 Subnet Reference IP Address” comes in a lot of handy above):
2402:9400:1234:1234::/64
2402:9400:1234:123X::/60
2402:9400:1234:12XX::/56
2402:9400:1234:1XXX::/52
2402:9400:1234:XXXX::/48
2402:9400:123X:XXXX::/44
2402:9400:12XX:XXXX::/40
IPv6 Address Scopes:
::/128 unspecified address
::1/128 localhost
fe80::/10 link local
fc00::/7 unique local unicast (RFC 4193)
fc00::/8 centrally assigned by unkown, routed within a site (RFC 4193)
fd00::/8 free for all, global ID must be generated randomly with pseudo-random algorithm, routed within a site (RFC 4193)
ff00::/8 multicast, following after the prefix ff there are 4 bits for flags and 4 bits for the scope
::ffff:0:0/96 IPv4 to IPv6 Address, eg: ::ffff:10.10.10.10 (RFC 4038)
2000::/3 global unicast
2001::/16 /32 subnets assigned to providers, they assign /48, /56 or /64 to the customer
2001:db8::/32 reserved for use in documentation
2001:678::/29 Provider Independent (PI) adresses and anycasting TLD nameservers
2002::/16 6to4 scope, 2002:c058:6301:: is the 6to4 public router anycast (RFC 3068)
Interface Configuration Linux:
#ifconfig eth0 inet6 add 2402:9400:1234:1234::1/64
Configuring SLAAC (auto configuration) on Redhat/CentOS flavors of Linux: You can do this by enabling IPv6 on an interface that is already configured automatically on boot.
IPv6 Command Line Tools:
ping6- IPv6 ping tool
traceroute6- IPv6 tracing tool
tracepath6 – IPv6 tracing tool
ip -6 – For configuring/viewing IPv6 interfaces and routes
ipv6calc – IPv6 subnet calculator
tcpdump ip6 – packet sniffing on IPv6
snoop inet6 – packet sniffing on IPv6