From: Mike Bartz (no email)
Date: Tue Aug 25 2009 - 16:21:42 EDT
On Mon, Aug 24, 2009 at 4:59 PM, Nick Hilliard <> wrote:
> On 24/08/2009 19:03, Holmes,David A wrote:
>> Additionally, and perhaps most significantly for deterministic network
>> design, the copper cards share input hardware buffers for every 8 ports.
>> Running one port of the 8 at wire speed will cause input drops on the
>> other 7 ports. Also, the cards connect to the older 32 Gbps shared bus.
> IMO, a more serious problem with the 6148tx and 6548tx cards is the
> internal architecture, which is effectively six internal managed gigabit
> ethernet hubs (i.e. shared bus) with a 1M buffer per hub, and each hub
> connected with a single 1G uplink to a 32 gig backplane. Ref:
> In Cisco's own words: "These line cards are oversubscription cards that are
> designed to extend gigabit to the desktop and might not be ideal for server
> farm connectivity". In other words, these cards are fine in their place,
> but they are not designed or suitable for data centre usage.
> I don't want to sound like I'm damning this card beyond redemption - it has
> a useful place in this world - but at the expense of reliability,
> manageability and configuration control, you will get useful features
> (including broadcast/unicast flood control) and in many situations very
> significantly better performance from a recent SRW 48-port linksys gig
> switch than from one of these cards.
We experienced the joy of using the X6148 cards with a SAN/ESX cluster.
Lots of performance issues! A fairly inexpensive solution was to switch to
the X6148A card instead, which does not suffer the the 8:1
oversubscription. It also supports MTU's larger than 1500, which was
another shortcoming of the older card.
-- Mike Bartz