[27342] in North American Network Operators' Group
Re: Cisco - ip verify unicast reverse-path
daemon@ATHENA.MIT.EDU (Craig A. Huegen)
Sun Feb 13 02:17:18 2000
Date: Sat, 12 Feb 2000 23:14:19 -0800
From: "Craig A. Huegen" <chuegen@quadrunner.com>
To: Paul Ferguson <ferguson@cisco.com>
Cc: trall@almaden.ibm.com, nanog@merit.edu
Message-ID: <20000212231419.A669@quadrunner.com>
Mime-Version: 1.0
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In-Reply-To: <4.2.2.20000212182722.00a556d0@lint.cisco.com>; from Paul Ferguson on Sat, Feb 12, 2000 at 06:35:50PM -0500
Errors-To: owner-nanog-outgoing@merit.edu
On Sat, Feb 12, 2000 at 06:35:50PM -0500, Paul Ferguson wrote:
==>The "ip verify unicast reverse-path" interface command (also known
==>as Unicast RPF, or Reverse-Path Forwarding check) requires CEF to
==>be in used in order to use this feature. This is because CEF separates
==>the RIB and FIB, and the FIB check is used that ensure that packets
==>received on an interface with this feature enabled are not forwarded
==>unless a valid path on the same interface exists back to the originating
==>source.
Sometimes saying "a valid path" is confusing. For an incoming packet, the
router checks to make sure that it will route back to the packet's source
address through the interface it came in on.
/cah
