Subject: question about router behavior

From: Yukiyo Akisada <[email-masked]>
Date: Wed, 1 Dec 2004 16:31:45 +0900

Hi, all.

I have a question about a router behavior.
rfc2461 and 2461bis assume that
the router can stop packet forwarding without disabling to send RA.

    draft-ietf-ipv6-2461bis-01.txt
    6.2.5.  Ceasing To Be An Advertising Interface
    ------------------------------------------------------------------------
    2555    Note that system management may disable a router's IP forwarding
    2556    capability (i.e., changing the system from being a router to being a
    2557    host), a step that does not necessarily imply that the router's
    2558    interfaces stop being advertising interfaces.  In such cases,
    2559    subsequent Router Advertisements MUST set the Router Lifetime field
    2560    to zero.
    ------------------------------------------------------------------------

But if a router stops packet forwarding, it should be a host.

    draft-ietf-ipv6-2461bis-01.txt
    2.  TERMINOLOGY
    2.1.  General
    ------------------------------------------------------------------------
    229    router      - a node that forwards IP packets not explicitly
    238                  addressed to itself.
    239
    240    host        - any node that is not a router.
    ------------------------------------------------------------------------

And rfc2461 and 2461bis also says the host never send RA.

    draft-ietf-ipv6-2461bis-01.txt
    6.2.4.  Sending Unsolicited Router Advertisements
    ------------------------------------------------------------------------
    2496    A host MUST NOT send Router Advertisement messages at any time.
    ------------------------------------------------------------------------

I think,
when the router stops packet forwarding,
the router also should stop sending RA
as like as other 3 cases specified in section 6.2.5.

    draft-ietf-ipv6-2461bis-01.txt
    6.2.5.  Ceasing To Be An Advertising Interface
    ------------------------------------------------------------------------
    2527    An interface may cease to be an advertising interface, through
    2528    actions of system management such as:
    2529 
    2530       - changing the AdvSendAdvertisements flag of an enabled interface
    2539         from TRUE to FALSE, or
    2540 
    2541       - administratively disabling the interface, or
    2542 
    2543       - shutting down the system.
    ------------------------------------------------------------------------

What is the difference from other 3 situations?

Thanks.

----
Yukiyo Akisada <[email-masked]>

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From: Markku Savela <[email-masked]>
Date: Wed, 1 Dec 2004 11:09:19 +0200

> the router can stop packet forwarding without disabling to send RA.

Perhaps, so that one could have a configuration with multiple routers, one
advertising only as default router, and no prefixes. And, another that
would advertise the prefixes, but have router lifetime = 0 (e.g., is
not a default router).

There is also "preferred route option", a router that is not default
router (lifetime = 0), but still routes some specificic prefixes.

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From: Yukiyo Akisada <[email-masked]>
Date: Thu, 2 Dec 2004 08:56:13 +0900

Hi, Markku.
Thanks for your comment.

On Wed, 1 Dec 2004 11:09:19 +0200

> router (lifetime = 0), but still routes some specificic prefixes.

But in these case,
the another router advertising lifetime=0
doesn't need to stop packet forwarding functionality.

Especially,
the latter case needs to use packet forwarding functionality.

These cases are realizable if routers change only RA configuration.
How do you think about this?

Thank you.

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