Remember, when we abbreviate an ipv6 address all leading zeros are reduced to a single 0.
E.g
0003 would just become 03
When there are geoups of 4 zeros these can be represented as a single 0 or as a double colon ::
But we can only use the :: once so when summarizing an address containing multiple groups of 4 0s one after the other they can all be abbreviated to a single ::
Eg
fe80:0000:0000:0000:0210:5aff:feaa:20a2 would become fe80::210:5aff:feaa:20a2
Therefore it is perfectly valid to abbreviate an address of 0000:0000:0000:0000:0000:0000:0000:0000 /0 to just ::/0
0.0.0.0/0 0::0/0
You didn’t specify it couldn’t be in CIDR block notation…
::/0
Remember, when we abbreviate an ipv6 address all leading zeros are reduced to a single 0.
E.g
0003 would just become 03
When there are geoups of 4 zeros these can be represented as a single 0 or as a double colon ::
But we can only use the :: once so when summarizing an address containing multiple groups of 4 0s one after the other they can all be abbreviated to a single ::
Eg
fe80:0000:0000:0000:0210:5aff:feaa:20a2 would become fe80::210:5aff:feaa:20a2
Therefore it is perfectly valid to abbreviate an address of 0000:0000:0000:0000:0000:0000:0000:0000 /0 to just ::/0
Eh, I’ve seen some software internally prefer 0::0 instead of just ::0 or :: . Notation wise though you are correct, it is unnecessary.