Regarding Source Address Selection. - TCP-IP

This is a discussion on Regarding Source Address Selection. - TCP-IP ; Hi As per RFC 3484, Implementations may also use the choice of router to influence the choice of source address. For example, suppose a host is on a link with two routers. Router A is advertising a global prefix A ...

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Thread: Regarding Source Address Selection.

  1. Regarding Source Address Selection.

    Hi

    As per RFC 3484, Implementations may also use the choice of router to
    influence the choice of source address. For example, suppose a host is
    on a link with two routers. Router A is advertising a global prefix A
    and the Router B is advertising global prefix B. Then when sending via
    the router A, the host may prefer source addresses with prefix A and
    when sending via the router B, prefer source addresses with prefix B.

    Now my query is what happens when we use the source address advertised
    by Router A while sending packets via Router B? Does it affect the
    forwarding of packets in any sense?


  2. Re: Regarding Source Address Selection.

    "Mythili" writes:
    > As per RFC 3484, Implementations may also use the choice of router to
    > influence the choice of source address. For example, suppose a host is
    > on a link with two routers. Router A is advertising a global prefix A
    > and the Router B is advertising global prefix B. Then when sending via
    > the router A, the host may prefer source addresses with prefix A and
    > when sending via the router B, prefer source addresses with prefix B.
    >
    > Now my query is what happens when we use the source address advertised
    > by Router A while sending packets via Router B? Does it affect the
    > forwarding of packets in any sense?


    Generally, no.

    First of all, source address isn't really used by normal routing
    processes. Instead, IP datagrams are forwarded based on the
    destination address.

    The real issue is with the return packets -- when that destination
    decides to send a packet back to you (using address A), what happens?

    As long as your routing system is sane, both routers will understand
    how to forward that message back. If your routing system isn't sane,
    all bets are off.

    --
    James Carlson, KISS Network
    Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
    MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

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