# Example: Limiting the Number of Prefixes Used by DHCPv6 Clients

If you a configure a very large prefix range in an IPv6 local address pool, the number of prefixes that can be used from that range by DHCPv6 clients is limited to 1048576.

Consider the following example in which an IPv6 local address pool, largePrefixRange, is configured. The prefix range is specified by the starting prefix and its length as 3003:3003::/32.

host1(config)#ipv6 local pool largePrefixRange host1(config-v6-local)#prefix 3003:3003::/32 64 host1(config-v6-local)#end

The Total field of the output of the following show ipv6 local pool largePrefixRange and show ipv6 local pool commands indicates the number of prefixes that can be allocated to DHCPv6 clients: 1048756.

    host1#show ipv6 local pool largePrefixRange

    Pool : largePrefixRange
    -----------------------
    Utilization : 0
              Start                        End               Total    In Use
    -------------------------   -------------------------   -------   -------
    3003:3003::/64              3003:3003:ffff:ffff::/64    1048576   0
                                                 Preferred      Valid
              Start             Exclude   Util    Lifetime     Lifetime
    -------------------------   -------   ----   ----------   ----------
    3003:3003::/64              0         0      1 day        1 day

    host1#show ipv6 local pool
                             IPv6 Local Address Pools
                             ------------------------
          Pool                   Start                        End
    ----------------   -------------------------   -------------------------
    largePrefixRange   3003:3003::/64              3003:3003:ffff:ffff::/64
          Pool          Total    In Use
    ----------------   -------   -------
    largePrefixRange   1048576   0