Thanks, that does help to clear some things up...sort of. :-) Let me
see if I really understand the differences between Sup1A+MSFC and
Sup2+MSFC2.
In the first configuration, the Sup1A can use CatOS or SupIOS. The
MSFC operates as the MLS-RP and the Sup1A is the MLS-SE, right?
InterVLAN traffic is routed initially by the MSFC until a flow is
established, at which point the rest of the flow is hardware switched.
In the second configuration, instead of MLS we're using CEF and the
MSFC2 config looks just like a router with multiple interfaces running
CEF. There are no MLS-related configuration commands needed. Hmm...at
the moment I'm actually having a hard time differentiating between the
operation of MLS and CEF in this context.
I think I need to brush up on MLS (since I haven't researched it since
last year) and then read through CCO to see how they're implementing CEF
on these switches.
If Cisco is moving toward using only the SupIOS, I may have to start
thinking of the 6500 as a router with a bunch of switch ports instead of
a switch with some L3 routing functions built in. :-)
thanks,
John
>>> "dre" 6/26/01 1:49:37 PM >>>
""John Neiberger"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Okay, I'm thoroughly confused. I'm doing some research on this
platform
> because we'll be purchasing one later this year or early next year.
The
> documentation seems to be quite murky and the more I read, the less
> clear the picture is.
The entire Catalyst architecture is strange and piecemeal. I
understand
your
confusion and frustration.
> I see a few different issues that I need help with. The first is
> software. Which one to use? CatOS? Supervisor IOS? If I can only
do
> CEF with IOS, then if we get CatOS are we totally hosed and limited
to
> software forwarding of interVLAN traffic?
The original SUP1 MSM architecture of the Layer 3 Catalyst 6500 is
different than the SUP1A MSFC architecture is different than the SUP2
MSFC2 architecture. You can use the MSFC2 on the SUP1A, but you
don't get the advantage of CEF in Layer 3 switching like you would
with
the SUP2 MSFC2 combination. SUP1A has to use MLS. SUP2 has
to use CEF.
In the SUP2 MSFC2 architecture, CEF is downloaded from the MSFC2
to the PFC2 (another card on the SUP2), so CEF now forwards in
hardware. This happens whether you are running CatOS (Hybrid) or
Sup IOS (Native). If you are using DFC-enabled linecards, the CEF
table is also downloaded to each DFC (there can be up to two per
linecard, depending on which ones you are using). It is actually even
more complex than this, but I don't want to make your head spin.
The only real difference between CatOS and Sup IOS is support and
features.
CatOS + MSFC IOS is currently the software for the SUP2 MSFC2
architecture. This is changing in the next three months. Everything
currently only works properly for SUP2 MSFC2 under CatOS.
But three months from now, Cisco is changing directions with the
product
and moving completely to Sup IOS. All future work will be done for
Sup
IOS, but it is not available fully yet. The newest features are being
developed for Sup IOS like EoMPLS (which Cisco demonstrated on the
Catalyst 6500 / 7600 OSR at SuperComm). I believe that the Catalyst
6500 / 7600 OSR is the only product currently supporting EoMPLS (or
any of the AToM technologies), even though it doesn't yet support
MPLS-TE or MPLS-VPN. More details on EoMPLS are available at
http://www.cisco.com/warp/public/cc/pd/rt/7600osr/prodlit/emp76_tc.htm
> I see that the MSFC2 can do 650 Mbps+ of software-based forwarding.
Is
> this only referring to first-time routing of packets when no MLS
entries
> are present in the cache? If there are cached entries are they
> hardware-forwarded or are we still limited by the performance of the
> MSFC?
MSFC2 only does forwarding when there are no MLS entries in the
cache, yes, but this only would occur on the SUP1A architecture. With
SUP2, the MSFC2 would only do forwarding when there are no CEF
adjacencies or when packets are not-cef-switched (first packet
generally).
The benefit of having the Catalyst 6500 would be to use MLS with SUP1A
whenever possible and CEF with SUP2 (or to the DFC-enabled linecards)
whenever possible. This maximizes performance, because it's all done
in
hardware forwarding.
> We have a lot of interVLAN traffic and my worry is that as traffic
> volumes increase that our performance will suffer due to restraints
> present in the MSFC.
As long as everything stays in MLS (SUP1A) you will be ok. There is
a hashing algorithm problem that causes a maximum of 128k
destination-only
based flows, but many people have found that realisitically this number
is
much lower due to a hash collision that will result in packets forced
up to
the MSFC (1 or 2, doesn't matter). More details can be found at:
http://www.cisco.com/warp/public/473/35.html (at the bottom of the
page). Setting destination-only based flows (the default) and by
tuning
with MLS fast aging, you can possibly acheive up to 128k flows in MLS.
The MSFC will handle a lot of packets, still, however the performance
is
not optimal compared to MLS.
Even better would be to use SUP2 MSFC2 with DFC-enabled linecards.
They do not suffer from the problems of MLS and things like OSPF ECMP
work a lot better using CEF. The performance of CEF is much better.
Also, SUP2 MSFC2 with Sup IOS seems to be the product's overall
direction.
> Without IOS and CEF, once the MLS cache is populated, aren't any
> further packets hardware switched? If that's the case, I don't see
much
> need to get the Sup IOS. I seem to remember someone complaining
about
> the Sup IOS but I don't remember the details. Hmm...I suppose I
ought
> to check the archives, huh? :-)
>
> Anyway, any help anyone could offer would be greatly appreciated!
CatOS is what most people are comfortable with. It also support the
most features currently, but probably won't support any new features.
I don't know of any currently installed Sup IOS installations, and I
have
not used the code myself, however, there is no arguing that in three
months and down the road, Sup IOS will evolve as the preferred
software for the Catalyst 6500 / 7600 OSR architecture.
-dre
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