OSPFv3 basic question

[martin.bernier2]

Hello,

I have 2 questions concerning OSPFv3 with Address-Family (RFC 6969/5838):

1) Does the OSPFv3 IPv4 address family can establish directly a neighbour relationship with an OSPFv2 (IPv4) node (without redisbribution) ?

2) Does the "old" OSPFv3 based on RFC 5240 (without address family support) can establish directly a neighbour relationship with an OSPFv3 node based on RFC 6969/5838 (i'm talking of IPv6-only node of course) ?

Best regards,

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Martin

[Nagendra Kumar Nainar · Accepted solution]

Hi Martin,

1) Does the OSPFv3 IPv4 address family can establish directly a neighbour relationship with an OSPFv2 (IPv4) node (without redisbribution) ?

No. As like traditional limitation, OSPFv3 is not backward compatible with OSPFv2. OSPFv2 will send the hellos to 224.0.0.5 (IPv4 addr) while OSPFv3 wil lsend to FF02::5 (IPv6 address).

2) Does the "old" OSPFv3 based on RFC 5240 (without address family support) can establish directly a neighbour relationship with an OSPFv3 node based on RFC 6969/5838 (i'm talking of IPv6-only node of course) ?

This is something I was thinking to try in local setup for quite sometime and havent yet. Per section 2.4 of RFC5838, it should support it for IPv6 AF.

When an OSPFv3 router participates in an AF (sets the AF-bit in
      the Options field), it MUST discard Hello packets having the AF-
      bit clear in the Options field.  The only exception is the Base
      IPv6 unicast AF, where this check MUST NOT be done (for backward
      compatibility).

If someone have it tried and see a different behaviour, they can comment

HTH,

Nagendra

[martin.bernier2]

Thank you Nagendra,

This is really interesting, i just realized that even using IPv4 Address family in OSPFv6, hello packet are still sent to an IPv6 multicast address...

Regards,

[Harold Ritter · Accepted solution]

Salut Martin,

As Nagendra pointed out, RFC5838 is backward compatible and will therefore interoperate with previous versions of ospfv3 that support ipv6 unicast only.

Regards