Authoritative only based on interface

Barry Margolin barmar at genuity.net
Tue Jul 17 16:58:05 UTC 2001


In article <9j1q62$lb6 at pub3.rc.vix.com>, Jim Reid  <jim at rfc1035.com> wrote:
>This probably won't solve the problem. It will do more or less what
>the original poster asked, namely handle queries based on the
>interface that they were sent to. This is not necessarily the same
>thing as the interface that took delivery of the incoming packet which
>is what seems to have been originally asked. Most (all?) Unix TCP/IP
>implementations use the weak end system model. They accept packets for
>any of the local addresses for the host no matter which interface
>receives them. [See Stevens: Unix Network Programming Vol1 or TCP/IP
>Illustrated Vol2.] There's usually no way of telling which interface
>actually received the query. Packets come off the wire and the host's
>network interface device drivers put them into one queue for going up
>the kernel's TCP/IP stack.

If the upstream router doesn't have a route for the internal address via
the external address, and it has source routing disabled, then the external
interface should never receive traffic for the internal address.
(Exception: a machine on the external LAN could have a static route for the
internal address via the external address.)

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.


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