Create 6rd interface:

/interface 6to4 add !keepalive name=6rd-wan-centurylink remote-address=205.171.2.64

Add to WAN interface list:

/interface list member add interface=6rd-wan-centurylink list=WAN

Add route:

/ipv6 route add disabled=no dst-address=2000::/3 gateway=6rd-wan-centurylink routing-table=main suppress-hw-offload=no

Add script named like update-6rd. Edit the first two variables and then run the script to create IPv6 pool.

# Configuration
:local ipv4interface "vlan201-wan"; # Name of the WAN interface to get IPv4 address from
:local ipv6pool "pool-6rd-centurylink"; # Name of IPv6 pool

# Helper function to convert decimal (0-255) to a two-character hex string
:local decToHex do={
    :local hexChars "0123456789abcdef";
    :local num [:tonum $1];
    :local high ($num / 16);
    :local low ($num - ($high * 16));
    :return ([:pick $hexChars $high ($high + 1)] . [:pick $hexChars $low ($low + 1)]);
}

# 1. Get the current IPv4 address from the interface
:local ipInfo [/ip address find interface=$ipv4interface];
:if ([:len $ipInfo] = 0) do={
    :log error "6RD Script: No IPv4 address found on interface $ipv4interface";
    :error "No IPv4 address found";
}
:local fullIp [/ip address get [:pick $ipInfo 0] address];

# 2. Strip the CIDR subnet mask (e.g., /24) from the IP
:local slashPos [:find $fullIp "/"];
:local ipv4 [:pick $fullIp 0 $slashPos];

# 3. Parse the IPv4 address into 4 separate octets
:local dot1 [:find $ipv4 "." 0];
:local dot2 [:find $ipv4 "." ($dot1 + 1)];
:local dot3 [:find $ipv4 "." ($dot2 + 1)];

:local octet1 [:pick $ipv4 0 $dot1];
:local octet2 [:pick $ipv4 ($dot1 + 1) $dot2];
:local octet3 [:pick $ipv4 ($dot2 + 1) $dot3];
:local octet4 [:pick $ipv4 ($dot3 + 1) [:len $ipv4]];

# 4. Convert each octet to Hexadecimal
:local hex1 [$decToHex $octet1];
:local hex2 [$decToHex $octet2];
:local hex3 [$decToHex $octet3];
:local hex4 [$decToHex $octet4];

# 5. Construct the 6RD IPv6 Prefix
:local newPrefix "2602:$(hex1):$(hex2)$(hex3):$(hex4)00::/56";

# 6. Apply to the IPv6 Pool
:local poolExists [/ipv6 pool find name=$ipv6pool];

:if ([:len $poolExists] > 0) do={
    # Pool exists, check if the prefix needs updating to prevent flash writes
    :local currentPrefix [/ipv6 pool get $poolExists prefix];
    :if ($currentPrefix != $newPrefix) do={
        :log info "6RD Script: IP changed. Updating pool from $currentPrefix to $newPrefix";
        
        # Find all IPv6 addresses tied to this pool
        :local poolAddrs [/ipv6 address find from-pool=$ipv6pool];
        
        # Disable them so the pool can be modified
        :if ([:len $poolAddrs] > 0) do={
            :log info "6RD Script: Disabling associated IPv6 addresses...";
            /ipv6 address disable $poolAddrs;
            # Give RouterOS a second to flush the "in use" status
            :delay 1s; 
        }
        
        # Update the pool prefix
        /ipv6 pool set $poolExists prefix=$newPrefix prefix-length=64;
        :log info "6RD Script: Updated $ipv6pool prefix successfully.";
        
        # Re-enable the addresses (RouterOS will automatically recompute the new IPs from the new prefix)
        :if ([:len $poolAddrs] > 0) do={
            :log info "6RD Script: Re-enabling associated IPv6 addresses...";
            /ipv6 address enable $poolAddrs;
        }
    } else={
        :log debug "6RD Script: IP has not changed. Pool prefix is up to date.";
    }
} else={
    # Pool doesn't exist, create it
    /ipv6 pool add name=$ipv6pool prefix=$newPrefix prefix-length=64;
    :log info "6RD Script: Created $ipv6pool with prefix $newPrefix";
}

Add addresses from pool to 6rd interface and to each LAN interface, example:

/ipv6 address add address=::/64 from-pool=pool-6rd-centurylink eui-64=yes interface=6rd-wan-centurylink
/ipv6 address add address=::/64 from-pool=pool-6rd-centurylink eui-64=yes interface=vlan142-lan
/ipv6 address add address=::/64 from-pool=pool-6rd-centurylink eui-64=yes interface=vlan300-lan2

In DHCPv4 client add script to run script:

:if ($bound = 1) do={
/system script run update-6rd
}

When DHCP client binds to IPv4 address, script will run and generate new IPv6 /56 prefix and update IPv6 address pool. It disables all addresses using the pool, updates the pool, and re-enables the addresses. Mikrotik automatically chooses /64 subnets from the pool. You can use 16 subnets.