IPv6Interface Config

ipv6 nd managed-config-flag

Sets the M flag in RA messages to direct clients to use stateful DHCPv6 for address assignment.

Syntax·Interface Config

ipv6 nd managed-config-flag

When to Use This Command

Enabling stateful DHCPv6 on a segment where centralized address management is required.
Overriding SLAAC to force clients to obtain addresses from DHCPv6.
Enterprise environments requiring address tracking and control.
Used alongside 'ipv6 dhcp server' to complete stateful DHCPv6 setup.

Command Examples

Enable stateful DHCPv6 on LAN interface

R1(config)# interface GigabitEthernet0/1
R1(config-if)# ipv6 nd managed-config-flag
R1(config-if)# ipv6 nd other-config-flag

R1(config-if)#

M=1 tells clients to get an address from DHCPv6. O=1 tells clients to also get DNS/domain from DHCPv6. In stateful DHCPv6, both flags are typically set together.

Verify RA flags in packet capture / show command

R1# show ipv6 interface GigabitEthernet0/1

GigabitEthernet0/1 is up, line protocol is up
  IPv6 is enabled, link-local address is FE80::1
  Global unicast address(es):
    2001:db8:1::1, subnet is 2001:db8:1::/64
  ND DAD is enabled, number of DAD attempts: 1
  ND reachable time is 30000 milliseconds
  ND advertised reachable time is 0 (unspecified)
  ND advertised retransmit interval is 0 (unspecified)
  ND router advertisements are sent every 200 seconds
  ND router advertisements live for 1800 seconds
  ND advertised default router preference is Medium
  Hosts use stateful autoconfig for addresses.
  Hosts use DHCP to obtain other configuration.

'Hosts use stateful autoconfig for addresses' confirms M=1. 'Hosts use DHCP to obtain other configuration' confirms O=1. Together these direct clients to use full stateful DHCPv6.

Understanding the Output

No direct output from the command. Verify with 'show ipv6 interface [intf]' — look for 'Hosts use stateful autoconfig for addresses' (M=1) vs 'Hosts use stateless autoconfig for addresses' (M=0). This command affects the RA messages clients receive, not the router's own behavior.

CCNA Exam Tips

CCNA exam tip: M flag = Managed = get IPv6 ADDRESS from DHCPv6 (stateful). O flag = Other = get DNS/domain only from DHCPv6 (stateless).

CCNA exam tip: If M=1, clients should also have O=1 to get DNS from DHCPv6 (best practice).

CCNA exam tip: SLAAC (A=1, default) generates addresses from the RA prefix. When M=1, clients should request from DHCPv6 instead.

CCNA exam tip: The M and O flags are set on the ROUTER interface — they affect what CLIENT behavior is signaled.

Common Mistakes

Mistake 1: Setting M flag without configuring a DHCPv6 server or relay on the interface — clients try DHCPv6 but get no response.

Mistake 2: Confusing M and O flags — M is for addresses, O is for other config (DNS). Many candidates mix these up on the exam.

Mistake 3: Setting M flag on the wrong interface (server-facing instead of client-facing).

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 dhcp server [pool-name]

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 nd other-config-flag

Sets the Other (O) flag in IPv6 Router Advertisement (RA) messages. When O=1, clients that use SLAAC for their address are also instructed to contact a DHCPv6 server for additional configuration parameters such as DNS servers and domain names.

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