Partial vs Full tables

Drew Weaver drew.weaver at
Mon Jun 15 12:35:40 UTC 2020

This is just my experience so do whatever you want with that.

The only time we have ever noticed any sort of operational downside of using uRPF loose was when NTTs router in NYC thought a full table was only 500,000 routes a few years back.

That is a fairly real consideration though. =)

-----Original Message-----
From: NANOG <nanog-bounces at> On Behalf Of William Herrin
Sent: Thursday, June 11, 2020 12:18 PM
To: brad dreisbach <bradd at>
Cc: nanog at
Subject: Re: Partial vs Full tables

On Thu, Jun 11, 2020 at 9:08 AM brad dreisbach <bradd at> wrote:
> uRPF absolutely kills the pps performance or your hardware due to the 
> packet having to be recirculated to do the check(at least this is the 
> case on every platform that ive ever tested it on). use acl's to protect your edge.

Hi Brad,

Don't the ACLs generally live in a partition of the TCAM too? So you're going from two constant-time TCAM lookups per packet (route,
acls) to three (route, urpf, acls)? Not rhetorical; getting close to the edge of my knowledge here.

Bill Herrin

William Herrin
bill at

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