On 2013-06-02 13:14, Gert Doering wrote:
Hi,
On Sun, Jun 02, 2013 at 05:49:05PM +0200, Ivan Pepelnjak wrote:
I thought it was urban lore until I started digging into data sheets for
various DC switches covered in my DC Fabrics webinar (yeah, couldn't resist ;)
All high-speed DC switches use some variant of TCAM-based forwarding.
Most of them have shared TCAM for IPv4 and IPv6 with IPv6 table
size being 1/2 IPv4 table size. Draw your own conclusions.
Insufficient data to draw conclusions. It could be that "forwarding
performance for *all* IPv6 is only half the pps rate as for IPv4" (due
to "alway doing two lookups"), or anything else, or a combination of
that.
I'm not sure about other switches, but for the Catalyst 3750/3750G, it
means some quirks with IPv6 ACLs. The 3750/3750D can do ACLs on full
/128's, but only if the lower 64 bits are EUI64. Otherwise the ACLs
only support /64's or shorter. As I understand it, this is because
Cisco made room for IPv6 in the TCAM by encoding the tcp/udp port number
into bits 89-104 of the IPv6 address. Fortunately the 3750-E doesn't
have this limitation.
References:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_52_se/configuration/guide/swv6acl.html#wp4334642
https://supportforums.cisco.com/thread/2083329
