nanog mailing list archives
Re: IP4 address conservation method
From: "Ricky Beam" <jfbeam () gmail com>
Date: Wed, 05 Jun 2013 18:25:52 -0400
On Wed, 05 Jun 2013 12:06:49 -0400, William Herrin <bill () herrin us> wrote:
... Since the Linux kernel already mishandles arp by default, you're probably begging for unexpected behavior. Double down on that if the customer controls the server image.
I won't argue against calling Linux "wrong". However, the linux way of dealing with ARP is well tuned for "host" and not "router" duty. It's just not designed for the kernel to maintain huge arp tables for extended periods. Generally, a host speaks to very few L2 neighbors. Even a "server" tends to speak to few of it's L2 neighbors -- esp. for an internet service (www, ftp, irc, etc.). However, a ROUTER speaks to everything on most of it's links. As such, out-of-the-box, linux makes for a very BAD router... it's neighbor cache goes "stale" in 30s (avg), and entries are dropped on a scale of minutes. Real Routers(tm) hold on to arp's for *hours* -- because broadcast traffic requires CPU attention.
That said, I do use a stripped debian box as an inter-vlan router. You don't want to see the pages of tweaks it's taken to stop it being a broadcast storm generator. (and no, "arpd" is stupid hack.) It's a beautiful thing to run "tcpdump ... broadcast" and see no packets!
(And I'm not too happy with the BS 32 interface limit for multicast routing.)
--Ricky
Current thread:
- IP4 address conservation method Mikael Abrahamsson (Jun 04)
- Re: IP4 address conservation method Dan White (Jun 05)
- Re: IP4 address conservation method Blake Hudson (Jun 06)
- Re: IP4 address conservation method Tore Anderson (Jun 06)
- Re: IP4 address conservation method Blake Hudson (Jun 06)
- Re: IP4 address conservation method William Herrin (Jun 05)
- Re: IP4 address conservation method Mikael Abrahamsson (Jun 05)
- Re: IP4 address conservation method William Herrin (Jun 05)
- Re: IP4 address conservation method Mikael Abrahamsson (Jun 05)
- Re: IP4 address conservation method Dan White (Jun 05)
- Re: IP4 address conservation method Mikael Abrahamsson (Jun 05)
- Re: IP4 address conservation method Dan White (Jun 05)
- Re: IP4 address conservation method Ricky Beam (Jun 05)
- Re: IP4 address conservation method William Herrin (Jun 05)
- Re: IP4 address conservation method Bjørn Mork (Jun 06)
- Re: IP4 address conservation method William Herrin (Jun 06)
- Re: IP4 address conservation method Jimmy Hess (Jun 06)
- Re: IP4 address conservation method William Herrin (Jun 06)
- Re: IP4 address conservation method Bjørn Mork (Jun 07)
- Re: IP4 address conservation method rdrake (Jun 05)
- Re: IP4 address conservation method Jimmy Hess (Jun 05)