OSPF IPv6 Extensions

V6 Area Option

• Supports both IPv4 and IPv6 addresses
• May maintain two routing tables or single IPv6 routing table
  • If single routing table must translate IPv4 addresses to IPv6 address
• V6 area may be stub area, transit area (including backbone), NSSA area
• Runs on top of IPv6
• All routers in v6 area must agree on IPv4 support or routing may break
  • All or none

Topology

• IPv6 in area 1.1.1.1 only
• Area 1.1.1.1 networks only reachable to rest of AS if networks are translated or have both v4 and v6 addresses

             _______________________________
            /                               \
           /                                 \
           |        Area 0.0.0.0 (BB)        | 
           \                                 /
            \_______________________________/
             __|__                     __|__
            |     |                   |     |
            |_____|                   |_____|
       ________|_______            ______|_________ 
      /                \          /                \
      |  Area 1.1.1.1  |          |  Area 2.2.2.2  |
      |      IPv6      |          |                |
      \________________/          \________________/

Topology

• IPv4 networks (from area 2.2.2.2) sent through AS
• IPv6 networks only reachable to area 2.2.2.2 if other areas also have IPv4 networks (or are translated)

             _______________________________
            /                               \
           /        Area 0.0.0.0 (BB)        \
           |              IPv6               | 
           \                                 /
            \_______________________________/
             __|__                     __|__
            |     |                   |     |
            |_____|                   |_____|
       ________|_______            ______|_________ 
      /                \          /                \
      |  Area 1.1.1.1  |          |  Area 2.2.2.2  |
      |      IPv6      |          |                |
      \________________/          \________________/

Packet Formats

• Identical to IPv4 formats (Hellos, DD, LsReq) but have bigger addresses
  • Link-state ID field is 128 bits
  • Advertising router field is 128 bits
  • Area ID field is 128 bits
• Net mask field is 32 bits
  • Identifies number of bits of a contiguous network mask

Link-State Advertisements

• Correspond to current OSPF LSA types
  • Type 17 = Type 1 (router links)
  • Type 18 = Type 2 (network links), etc.
• 128-bit LS ID, 128-bit router ID, 32-bit mask length field
• IPv4 LSAs (summaries, externals) may be flooded into v6 areas but v6 LSAs are never flooded into IPv4 areas

V6 Router Links Advertisements

• Includes both IPv4 and IPv6 links
  • Equivalent link types but with big fields
  • E.g., Type 17 = Type 1: point-to-point connection
• New router link type (21) for IPv4 router ID
  • SPF calculations
  • Needed for AS boundary summary LSAs

Router Link Fragmentation

• Needed for bigger addresses
  • Avoid IP fragmentation
• Advertising router identifies router
• Link-state ID identifies fragment

Opaque LSA

• Method to distribute information using OSPF database distribution mechanism
• Uses the `P' (propagate) bit as defined in NSSA option
  • Added by originator of LSA
• Flag border routers to redistribute LSA to other v6 areas

Opaque LSA Usage

• Flood AS path information (BGP/IDRP)
• Flood public key information
• If IPX addresses embedded into IPv6 can use opaque to flood SAP information
• QoS information/attributes
• LS ID
  • First 32 bits type
  • Next 96 bits are defined by type

Migration

• Run v6 as backbone
• Run v6 as stub areas
• Single or v4 and v6 routing tables
• Can run existing IPv4 protocols (RIP, BGP) as well as IPv6