More ideally, you give every end site a /48 if they want more than one network. Owen On Apr 4, 2011, at 5:59 PM, Mark Andrews wrote:
In message <690D7D20D2507C44BA8066926B2009890867FA@ES1002.ic-sa.com>, Michael R uiz writes:
Hello All,
I am looking for some good reading material to get a better= understanding of IPV6. I know how to convert HEX into decimal format. Wh= at I am looking for is how to under the CIDR notation and break them out in= to subnets. Thank you in advance.
If you think in hex its straight forward to do CIDR in IPv6. There are only three groupings on a non nibble boundaries. You also display the entire 128 bits with the least significant bits set to zero. The :: notation is used to shorten the displayed address.
e.g for a /57, /58 and /59 with leading bits of 2001:23bc:fe8d:b200::/56 you would have.
/57 {0,1,2,3,4,5,6,7} {8,9,a,b,c,d,e,f} 2001:23bc:fe8d:b200::/57 2001:23bc:fe8d:b280::/57 /58 {0,1,2,3} {4,5,6,7} {8,9,a,b} {c,d,e,f} 2001:23bc:fe8d:b200::/58 2001:23bc:fe8d:b240::/58 2001:23bc:fe8d:b280::/58 2001:23bc:fe8d:b2c0::/58 /59 {0,1} {2,3} {4,5} {6,7} {8,9} {a,b} {c,d} {e,f} 2001:23bc:fe8d:b200::/59 2001:23bc:fe8d:b220::/59 2001:23bc:fe8d:b240::/59 2001:23bc:fe8d:b260::/59 2001:23bc:fe8d:b280::/59 2001:23bc:fe8d:b2a0::/59 2001:23bc:fe8d:b2c0::/59 2001:23bc:fe8d:b2e0::/59
Note the last nibble before the :: is 0 and is there so that the final bits are all zeros. The following all represent the same cidr block.
2001:23bc:fe8d:b2e0::/59 2001:23bc:fe8d:b2e0:0000:0000:0000:0000/59 2001:23bc:fe8d:b2e0:0:0:0:0/59
Normally you just assign /64 subnets and delegate address blocks on nibble boundaries to end customers, e.g. /48, /52, /56 or /60. This means that end customers don't need do deal with cidr block if they don't want to. They can just route individual /64.
MAR.
-- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka@isc.org