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Re: NAT and age

To: Christian Karpp <xn@heidelbg.ibm.com>
Subject: Re: NAT and age
From: Darren Reed <darrenr@reed.wattle.id.au>
Date: Sat, 23 Dec 2006 00:40:27 +1100
Cc: ipfilter@coombs.anu.edu.au
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In-reply-to: <458BD3E1.7070601@heidelbg.ibm.com>
References: <458BD3E1.7070601@heidelbg.ibm.com>
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Christian Karpp wrote:
> Hi,
>
> I'd like to understand how aging of NAT entries work. I'm currently
> struggling with my NAT table filling up and never expiring any entries.
>
> I'm using only two rules:
> map en0 10.10.0.0/16 -> a.b.c.d/32 age 2
> rdr en0 a.b.c.d port 80 -> 10.10.20.4 port 80
>
> One machine on the private net does *a lot* of DNS queries and fills
> up the NAT table pretty quickly with entries like:
> MAP 10.10.10.3      51019 <- -> a.b.c.d      51019 [e.f.g.h 53]
>
> No entry ever expires as I can tell from an 'ipnat -s' thus when 30000
> lines have been added, no new connections will be handled. Neither by
> the MAP nor by the RDR statement. I have to manually flush the table
> ('ipnet -F') first to make things work again.
>
> I'm using a build of IPFilter v4.1.13, compiled with default options,
> running on AIX 5.3TL05

If you do "ipf -V" successively, do you see the value for "fr_ticks"
increase?

Darren


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