IPv6 on macOS

macOS gets three IPv6 addresses:

Address Type	Purpose	Lifespan	Defined By
Link-local	Local network communication	Always present	RFC 4291
Stable global	Persistent IPv6 identity (e.g., DNS, inbound)	Long-lived	RFC 7217
Temporary global	Privacy-protected for outbound use	Short-lived	RFC 4941

Troubleshooting commands:

• ifconfig -v en0

The stable global address (secured) has a long lifetime.

The temporary one has a shorter lifetime (rotated automatically by macOS).

Example:

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500 index 11
	eflags=452008d0<ADV_REPORT,ACCEPT_RTADV,TXSTART,ARPLL,NOACKPRI,ECN_ENABLE,CHANNEL_DRV,FASTLN_ON>
	options=6460<TSO4,TSO6,CHANNEL_IO,PARTIAL_CSUM,ZEROINVERT_CSUM>
	hwassist=703000<CSUM_PARTIAL,CSUM_ZERO_INVERT,MULTIPAGES,TSO_V4,TSO_V6>
	ether a0:9a:8e:90:a6:62
	inet6 fe80::10d9:bcb0:601f:16fa%en0 prefixlen 64 secured scopeid 0xb
	inet6 2602:ae:15a4:8001:424:837a:870:6095 prefixlen 64 autoconf secured
	inet6 2602:ae:15a4:8001:edf7:1b86:b5fc:9085 prefixlen 64 autoconf temporary
	inet 192.168.0.106 netmask 0xffffff00 broadcast 192.168.0.255
	netif: EAC9C25E-FC35-4485-A08E-34485A15664D
	flowswitch: 1F20873E-7382-4A87-9768-EED8C7BCAB99
	nd6 options=201<PERFORMNUD,DAD>
	media: autoselect
	status: active
	generation id: 11
	type: Wi-Fi
	agent domain:Skywalk type:NetIf flags:0xa443 desc:"Userspace Networking"
	agent domain:Skywalk type:FlowSwitch flags:0x4483 desc:"Userspace Networking"
	agent domain:WiFiManager type:CallInProgress flags:0x3d desc:"WiFi"
	link quality: 100 (good)
	state availability: 0 (true)
	scheduler: FQ_CODEL (driver managed)
	uplink rate: 88.31 Mbps [eff] / 146.08 Mbps
	downlink rate: 88.31 Mbps [eff] / 146.08 Mbps [max]
	qosmarking enabled: yes mode: none
	low power mode: disabled
	multi layer packet logging (mpklog): disabled
	routermode4: disabled
	routermode6: disabled

• Global IPv6 privacy settings sysctl net.inet6.ip6.use_tempaddr

Example:

net.inet6.ip6.use_tempaddr: 1

Output meanings:

0 → Privacy extensions disabled (only stable addresses)

1 → Enabled (temporary addresses used)

2 → Enabled and always preferred for outgoing connections (default on macOS)

• This shows neighbor cache ndp -a

Neighbor                                Linklayer Address  Netif Expire    St Flgs Prbs
2602:ae:15a4:8001::1                    c:83:cc:fb:a1:7      en0 17s       R  R
2602:ae:15a4:8001:424:837a:870:6095     a0:9a:8e:90:a6:62    en0 permanent R
2602:ae:15a4:8001:edf7:1b86:b5fc:9085   a0:9a:8e:90:a6:62    en0 permanent R
fe80::e83:ccff:fefb:a107%en0            c:83:cc:fb:a1:7      en0 22s       R  R

• scutil --nwi

This shows the Network Interface Info (NWI) table and which IPv6 addresses are considered active/preferred for routing.

Network information

IPv4 network interface information
     en0 : flags      : 0x7 (IPv4,IPv6,DNS)
           address    : 192.168.0.106
           reach      : 0x00000002 (Reachable)

   REACH : flags 0x00000002 (Reachable)

IPv6 network interface information
     en0 : flags      : 0x7 (IPv4,IPv6,DNS)
           address    : 2602:ae:15a4:8001:424:837a:870:6095
           reach      : 0x00000002 (Reachable)

   REACH : flags 0x00000002 (Reachable)

Network interfaces: en0

• scutil

Using the network database to inspect the full interface configuration as known to networkd:

scutil
> show State:/Network/Interface/en0/IPv6

Example:

> show State:/Network/Interface/en0/IPv6
<dictionary> {
  Addresses : <array> {
    0 : fe80::10d9:bcb0:601f:16fa
    1 : 2602:ae:15a4:8001:424:837a:870:6095
    2 : 2602:ae:15a4:8001:edf7:1b86:b5fc:9085
  }
  Flags : <array> {
    0 : 1024
    1 : 1088
    2 : 192
  }
  PrefixLength : <array> {
    0 : 64
    1 : 64
    2 : 64
  }
}
>