Regular expression that matches valid IPv6 addresses

Question :

Regular expression that matches valid IPv6 addresses,

Answer :

I’m having trouble writing a regular expression that matches valid IPv6 addresses, including those in their compressed form (with :: or leading zeros omitted from each byte pair).

Can someone suggest a regular expression that would fulfill the requirement?

I’m considering expanding each byte pair and matching the result with a simpler regex.

,

I was unable to get @Factor Mystic’s answer to work with POSIX regular expressions, so I wrote one that works with POSIX regular expressions and PERL regular expressions.

It should match:

  • IPv6 addresses
  • zero compressed IPv6 addresses
  • link-local IPv6 addresses with zone index
  • IPv4-Embedded IPv6 Address
  • IPv4-mapped IPv6 addresses
  • IPv4-translated addresses
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IPv6 Regular Expression:

(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))  

For ease of reading, the following is the above regular expression split at major OR points into separate lines:

# IPv6 RegEx  (  ([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|          # 1:2:3:4:5:6:7:8  ([0-9a-fA-F]{1,4}:){1,7}:|                         # 1::                              1:2:3:4:5:6:7::  ([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|         # 1::8             1:2:3:4:5:6::8  1:2:3:4:5:6::8  ([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|  # 1::7:8           1:2:3:4:5::7:8  1:2:3:4:5::8  ([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|  # 1::6:7:8         1:2:3:4::6:7:8  1:2:3:4::8  ([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|  # 1::5:6:7:8       1:2:3::5:6:7:8  1:2:3::8  ([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|  # 1::4:5:6:7:8     1:2::4:5:6:7:8  1:2::8  [0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|       # 1::3:4:5:6:7:8   1::3:4:5:6:7:8  1::8    :((:[0-9a-fA-F]{1,4}){1,7}|:)|                     # ::2:3:4:5:6:7:8  ::2:3:4:5:6:7:8 ::8       ::       fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|     # fe80::7:8%eth0   fe80::7:8%1     (link-local IPv6 addresses with zone index)  ::(ffff(:0{1,4}){0,1}:){0,1}  ((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}  (25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|          # ::255.255.255.255   ::ffff:255.255.255.255  ::ffff:0:255.255.255.255  (IPv4-mapped IPv6 addresses and IPv4-translated addresses)  ([0-9a-fA-F]{1,4}:){1,4}:  ((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}  (25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])           # 2001:db8:3:4::192.0.2.33  64:ff9b::192.0.2.33 (IPv4-Embedded IPv6 Address)  )    # IPv4 RegEx  ((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]).){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])  

To make the above easier to understand, the following “pseudo” code replicates the above:

IPV4SEG  = (25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])  IPV4ADDR = (IPV4SEG.){3,3}IPV4SEG  IPV6SEG  = [0-9a-fA-F]{1,4}  IPV6ADDR = (             (IPV6SEG:){7,7}IPV6SEG|                # 1:2:3:4:5:6:7:8             (IPV6SEG:){1,7}:|                      # 1::                                 1:2:3:4:5:6:7::             (IPV6SEG:){1,6}:IPV6SEG|               # 1::8               1:2:3:4:5:6::8   1:2:3:4:5:6::8             (IPV6SEG:){1,5}(:IPV6SEG){1,2}|        # 1::7:8             1:2:3:4:5::7:8   1:2:3:4:5::8             (IPV6SEG:){1,4}(:IPV6SEG){1,3}|        # 1::6:7:8           1:2:3:4::6:7:8   1:2:3:4::8             (IPV6SEG:){1,3}(:IPV6SEG){1,4}|        # 1::5:6:7:8         1:2:3::5:6:7:8   1:2:3::8             (IPV6SEG:){1,2}(:IPV6SEG){1,5}|        # 1::4:5:6:7:8       1:2::4:5:6:7:8   1:2::8             IPV6SEG:((:IPV6SEG){1,6})|             # 1::3:4:5:6:7:8     1::3:4:5:6:7:8   1::8             :((:IPV6SEG){1,7}|:)|                  # ::2:3:4:5:6:7:8    ::2:3:4:5:6:7:8  ::8       ::                    fe80:(:IPV6SEG){0,4}%[0-9a-zA-Z]{1,}|  # fe80::7:8%eth0     fe80::7:8%1  (link-local IPv6 addresses with zone index)             ::(ffff(:0{1,4}){0,1}:){0,1}IPV4ADDR|  # ::255.255.255.255  ::ffff:255.255.255.255  ::ffff:0:255.255.255.255 (IPv4-mapped IPv6 addresses and IPv4-translated addresses)             (IPV6SEG:){1,4}:IPV4ADDR               # 2001:db8:3:4::192.0.2.33  64:ff9b::192.0.2.33 (IPv4-Embedded IPv6 Address)             )  

I posted a script on GitHub which tests the regular expression:

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That’s the answer Regular expression that matches valid IPv6 addresses, Hope this helps those looking for an answer. Then we suggest to do a search for the next question and find the answer only on our site.

Disclaimer :

The answers provided above are only to be used to guide the learning process. The questions above are open-ended questions, meaning that many answers are not fixed as above. I hope this article can be useful, Thank you