IPv6 Addressing

Multicast Application to IPv6 Addressing

For information on Multicast Listener Discovery (MLD) refer to the chapter titled “Multicast Listener Discovery (MLD) Snooping”.

When MLD is enabled on an interface, you can use show ipv6 mld [ vlan < vid >] to list the active multicast group activity the switch has detected per interface from other devices.

IPv6 Multicast Address Format

The multicast address format has three principal sections in the leading 16 bits:

■identifier: ff (bits 1-8)

■flags: 0xxx (bits 9-12)

■scope: 0001 - 1110 (bits 13-16)

For related information, refer to RFC 4291.

Multicast Group Identification

Multicast ID, Flags and Scope (16 bits)

Group Identifier (112 bits)

1111 1111 0xxx xxxx : x...x : x...x : x...x : x...x : x...x : x...x : x...x

■multicast identifier: The first eight high-order bits, set to ff, identify the address as multicast.

■multicast flags: Bits 9-12 are multicast flags that provide additional information about the multicast address, as follows:

Bit IDOptionsUse

9

0

reserved

 

 

 

10 (R)

0

multicast address without PIM-SM rendezvous point

 

1

multicast address with PIM-SM rendezvous point

 

 

 

11 (P)

0

multicast address without prefix information from the

 

 

originating network

 

1

multicast address with prefix information from the originating

 

 

network

 

 

 

12 (T)

0

multicast address is permanent (well-known, and not

 

 

restricted by scope value)

 

1

multicast address is temporary (and used only within an

 

 

identified scope)

 

 

 

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