netdev - Re: increase the number of routing tables

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Message-ID: <CANj2EbdFc33ciZ02ZCF7=3sY1XTbCLrdfu4Mp_vLp4N94xu5Cw@mail.gmail.com>
Date:	Sat, 28 Jan 2012 23:20:33 -0500
From:	Simon Chen <simonchennj@...il.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: increase the number of routing tables

Thanks...

Here says 252 routing tables top... maybe that's too old:
http://linux-ip.net/html/routing-tables.html

I wonder if we can use a trie-tree for "ip rule" - linear evaluation
does not sound too good. But I'll be using a ton of iptables rules as
well, and I believe those are linear evaluation too :-(

On Sat, Jan 28, 2012 at 9:46 PM, Ben Greear <greearb@...delatech.com> wrote:
> On 01/28/2012 06:41 PM, Eric Dumazet wrote:
>>
>> Le samedi 28 janvier 2012 à 21:20 -0500, Simon Chen a écrit :
>>>
>>> Hey folks,
>>>
>>> To my limited knowledge, Linux currently supports 256 (255?) routing
>>> tables defined in /etc/iproute2/rt_tables.
>>>
>>> Is there a way to increase this number to something much larger? Are
>>> there performance/scalability concerns there? I am trying to have
>>> customized routing table for each IP address (using "ip rule add from
>>> xxx table yyy"). I am not sure exactly how many IPs I'll handle, but
>>> certainly more than 255...
>>>
>>
>> Its is possible, but probably not scalable.
>
>
> I've run with a few thousand routing tables and probably 5000 or so
> rules.  It seems to run OK....
>
>
>> You really should not have too many "ip rule" entries, since they are
>> evaluated linearly.
>
>
> For every packet, or maybe just until conn-track gets an entry
> for the connection?
>
> Thanks,
> Ben
>
>
> --
> Ben Greear <greearb@...delatech.com>
> Candela Technologies Inc  http://www.candelatech.com
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