IPv6

Bridge IPv6

This section covers IPv6 configuration for vmbrX bridges, based on the ifupdown2 backend (default).

Static IPv6

iface vmbr0 inet6 static
      address  2001:ded:beef:2::1/64

Configuration explanation:

• inet6 static: Specifies the use of a static IPv6 address
• address: Specifies the IPv6 address and prefix length (/64 is the standard subnet mask)

SLAAC Auto-configuration

iface vmbr0 inet6 auto
      autoconf 1
      accept_ra 2
      bridge-mcsnoop no

Configuration explanation:

• inet6 auto: Enables IPv6 auto-configuration
• autoconf 1: Enables SLAAC (Stateless Address Auto-Configuration)
• accept_ra 2: Accept Router Advertisements (RA)
  • 0 = Do not accept router advertisements
  • 1 = Accept only in non-forwarding mode
  • 2 = Accept even in forwarding mode (bridges typically operate in forwarding mode, so this must be set to 2)
• bridge-mcsnoop no: Disables multicast snooping on the bridge
  • This is critical for IPv6, as the Neighbor Discovery Protocol (NDP) relies on multicast
  • If not disabled, IPv6 multicast traffic may be incorrectly filtered, causing connectivity issues

Important Notes

1. Bridges, as forwarding devices, must use accept_ra 2 to correctly receive router advertisements
2. Disabling bridge-mcsnoop is essential for proper IPv6 operation, especially for the NDP protocol
3. Network service restart or system reboot is required for configuration changes to take effect