**To associate an IPv6 CIDR block with a subnet**
This example associates an IPv6 CIDR block with the specified subnet.
Command::
aws ec2 associate-subnet-cidr-block --subnet-id subnet-5f46ec3b --ipv6-cidr-block 2001:db8:1234:1a00::/64
Output::
{
"SubnetId": "subnet-5f46ec3b",
"Ipv6CidrBlockAssociation": {
"Ipv6CidrBlock": "2001:db8:1234:1a00::/64",
"AssociationId": "subnet-cidr-assoc-3aa54053",
"Ipv6CidrBlockState": {
"State": "associating"
}
}
}