[AusNOG] MTU Size on Ethernet carrier interconnects

[McDonald Richards]

Of course some of us still have a few POS interfaces with 4470 byte
restrictions so while 9216 is great, it's pretty hard to promise it network
wide unless there is a specific requirement to migrate all services to
support it.

In my experience, permitting IP transit with larger than 1500 byte MTUs also
led to some strange jumbo frame issues where the customer has their own
switched network between their provider and themselves and they haven't
properly configured it to handle the larger frame sizes.

The path of least resistance was just to set "ip mtu 1500" as standard on
all customer-facing IP transit services, IP transit points and peering
points.

Macca



From:  Lincoln Dale <ltd at aristanetworks.com>
Date:  Thu, 2 Feb 2012 17:10:30 +1100
To:  "Sean K. Finn" <sean.finn at ozservers.com.au>
Cc:  "Ausnog at ausnog.net" <Ausnog at ausnog.net>
Subject:  Re: [AusNOG] MTU Size on Ethernet carrier interconnects

In a world of utopia, everyone would just enable 9216 byte jumbo frames & be
done with it.
the reality is that a variety of 'ethenet' WAN services are implemented
using a variety of silicon which predates 9K jumbo frames, and some have
silicon that only enables 1500 byte or at best a 'baby giant' frame.

i doubt anyone has <1500 byte. thats not so useable. :)


cheers,

lincoln.

-- 
Lincoln Dale | Principal Engineer | Arista Networks
ltd at aristanetworks.com | +1 408 547 5782  | +61 417 457 965


On Thu, Feb 2, 2012 at 5:05 PM, Sean K. Finn <sean.finn at ozservers.com.au>
wrote:
> Flooded with private replies, thanks to all.
>  
> General consensus is minimum 1500MTU but many providers will do slightly
> higher, and some very very much higher.
>  
> S.
>  
> 
> From: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net]
> On Behalf Of Sean K. Finn
> Sent: Thursday, February 02, 2012 2:46 PM
> To: 'Ausnog at ausnog.net'
> Subject: [AusNOG] MTU Size on Ethernet carrier interconnects
> 
>  
> G¹day all.
>  
> What¹s considered a standard MTU size for bulk IPv4 Transit when delivered via
> Ethernet? (Assume as an Access port, not a trunk port).
>  
> Cheers,
> Sean.
>  
> 

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