On Fri, Apr 24, 1998 at 06:06:50PM -0500, John A. Tamplin wrote:
On Fri, 24 Apr 1998, Karl Denninger wrote:
Well, there is a simple knob for this:
If the Knob is turned "ON", then any packet from a source address which is not routed to the interface it came in on is dropped.
This works for static, dynamic, and all other kinds of routing. It will solve the problem and is trivial to implement - if any of the vendors care.
It doesn't work for asymmetric routing as you describe it above. If you modify your criteria to be that there are no valid routes out that interface, you would only break transient routing conditions, but depending on how the router stores routes it may not be possible (or desirable due to memory requirements) to implement.
John Tamplin Traveller Information Services jat@Traveller.COM 2104 West Ferry Way 205/883-4233x7007 Huntsville, AL 35801
Balderdash. That a route is *valid* doesn't mean its the best path or the one that the router will use. It means that the path is *valid*. You're confusing "valid" with "best". Besides, the issue here isn't transport level circuits (where such things matter); it is end-customer attachments, which are typically not multihomed and even if they are, they're also typically static routed. Someone running BGP4 with you isn't going to have this enabled on either end of that interface. I don't expect this to be usable on a backbone circuit. Then again, that's not where the problems are originating. -- -- Karl Denninger (karl@MCS.Net)| MCSNet - Serving Chicagoland and Wisconsin http://www.mcs.net/ | T1's from $600 monthly / All Lines K56Flex/DOV | NEW! Corporate ISDN Prices dropped by up to 50%! Voice: [+1 312 803-MCS1 x219]| EXCLUSIVE NEW FEATURE ON ALL PERSONAL ACCOUNTS Fax: [+1 312 803-4929] | *SPAMBLOCK* Technology now included at no cost