ipv6 dhcp server [pool-name]
Activates DHCPv6 server functionality on an interface using a configured pool.
Definition: ipv6 dhcp server [pool-name] is a Cisco IOS interface config command. Enables a DHCPv6 server on an interface and links it to a named DHCPv6 pool. Clients on that interface receive IPv6 addresses and parameters from the specified pool.
ipv6 dhcp server <pool-name>When to Use This Command
- Serving IPv6 addresses to LAN hosts from a router acting as DHCPv6 server.
- Enabling stateful DHCPv6 on a gateway interface.
- Providing stateless DHCPv6 (DNS/domain only) when combined with SLAAC.
- Required step after creating an 'ipv6 dhcp pool'.
Command Examples
Enable DHCPv6 server on LAN interface
R1(config)# interface GigabitEthernet0/1
R1(config-if)# ipv6 address 2001:db8:1::1/64
R1(config-if)# ipv6 dhcp server IPV6-CLIENTS
R1(config-if)# ipv6 nd managed-config-flagR1(config-if)#
The interface now serves DHCPv6 addresses from the IPV6-CLIENTS pool. The M flag tells clients to request an address from DHCPv6 instead of or in addition to SLAAC.
Verify active DHCPv6 server
R1# show ipv6 dhcp interface GigabitEthernet0/1GigabitEthernet0/1 is in server mode Using pool: IPV6-CLIENTS Preference value: 0 Hint from client: ignored Rapid-Commit: disabled
Confirms the interface is in server mode using the IPV6-CLIENTS pool. Preference 0 is the default (used for server selection when multiple DHCPv6 servers exist).
Understanding the Output
Verify with 'show ipv6 dhcp interface [intf]' to confirm server mode and pool. Use 'show ipv6 dhcp binding' to see active leases. If no clients appear in the binding table, check that the M or O flag is set on the interface and that clients are sending DHCPv6 Solicit messages.
CCNA Exam Tips
CCNA exam tip: 'ipv6 dhcp server' is configured per-interface, not globally. Each interface that serves clients needs this command.
CCNA exam tip: DHCPv6 uses UDP port 546 (client) and 547 (server) — different from IPv4 DHCP (67/68).
CCNA exam tip: For stateless DHCPv6 (DNS only, addresses from SLAAC), use the O flag but NOT the M flag.
CCNA exam tip: 'show ipv6 dhcp interface' and 'show ipv6 dhcp pool' are the two key verification commands.
Common Mistakes
Mistake 1: Referencing a pool name that doesn't exist or has a typo — no addresses are served.
Mistake 2: Forgetting to set the M or O flag on the interface — hosts fall back to SLAAC only.
Mistake 3: Configuring DHCPv6 server without configuring an IPv6 address on the interface — DHCPv6 requires the interface to be IPv6-enabled.
ipv6 dhcp server [pool-name] vs ipv6 dhcp pool [name]
These two commands are commonly confused because both are essential for configuring DHCPv6 on Cisco IOS, but one activates the service on an interface while the other defines the addressing and parameter pool. Understanding their distinct roles is critical for correct deployment.
| Aspect | ipv6 dhcp server [pool-name] | ipv6 dhcp pool [name] |
|---|---|---|
| Scope | Interface-specific; enables DHCPv6 service on a single interface | Global; defines pool configuration for entire router |
| Configuration mode | Interface configuration mode | Global configuration mode, then DHCPv6 pool sub-mode |
| Persistence | Only persists while interface exists and is enabled | Persists in running config regardless of interface state |
| Precedence | Links pool to interface; only one pool per interface | Creates pool; can be linked to multiple interfaces or none |
| Typical use | Activating stateless or stateful DHCPv6 on a specific LAN segment | Defining address range, DNS, domain, and other parameters for clients |
Use ipv6 dhcp server [pool-name] when you need to enable DHCPv6 service on a specific interface and tie it to an already-defined pool.
Use ipv6 dhcp pool [name] when you need to create or modify the pool parameters (e.g., address prefix, DNS servers) before or after attaching it to an interface.
Related Commands
ipv6 dhcp pool [name]
Creates a DHCPv6 server pool and enters DHCPv6 pool configuration mode. Used to configure stateful DHCPv6, where the server assigns IPv6 addresses and provides DNS/domain information to clients.
ipv6 nd managed-config-flag
Sets the Managed (M) flag in IPv6 Router Advertisement (RA) messages sent from this interface. When M=1, clients are instructed to obtain their IPv6 address from a DHCPv6 server (stateful DHCPv6) rather than using SLAAC.
show ipv6 dhcp binding
Displays active DHCPv6 address bindings — the list of IPv6 addresses that have been leased from the DHCPv6 server along with the client DUID (Device Unique Identifier), IAID, and lease expiry times.
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