ipv6 nd managed-config-flag
Sets the M flag in RA messages to direct clients to use stateful DHCPv6 for address assignment.
Definition: ipv6 nd managed-config-flag is a Cisco IOS interface config command. 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.
ipv6 nd managed-config-flagWhen 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-flagR1(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 GigabitEthernet0/1GigabitEthernet0/1 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).
ipv6 nd managed-config-flag vs ipv6 nd other-config-flag
These two commands are commonly confused because both set flags in IPv6 Router Advertisements that involve DHCPv6, but they serve different purposes: the managed-config-flag triggers stateful address assignment, while the other-config-flag triggers retrieval of additional configuration parameters without affecting address assignment.
| Aspect | ipv6 nd managed-config-flag | ipv6 nd other-config-flag |
|---|---|---|
| Scope | Interface configuration | Interface configuration |
| Flag Set | Managed (M) flag = 1 | Other (O) flag = 1 |
| Effect on Clients | Clients use DHCPv6 for IPv6 address (stateful DHCPv6) | Clients use SLAAC for address, plus DHCPv6 for extra parameters |
| Persistence | Active until removed with 'no ipv6 nd managed-config-flag' | Active until removed with 'no ipv6 nd other-config-flag' |
| Precedence | When set, clients ignore SLAAC for address; must use DHCPv6 | Works with SLAAC; O flag has no effect if M flag is set |
| Typical Use Case | Enterprise networks requiring central address management | Networks using SLAAC but needing DNS and other options from DHCPv6 |
Use ipv6 nd managed-config-flag when you want clients to obtain their IPv6 address exclusively via a DHCPv6 server, disabling SLAAC for address assignment.
Use ipv6 nd other-config-flag when you want clients to use SLAAC for their IPv6 address but still contact a DHCPv6 server for additional configuration parameters like DNS servers.
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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