RE: Design issue

Regarding VSS --

There are three DAD methods - PaGP+, BFD and Fast Hellos. You really should
look at what SXI 4+ introduced - the ability to have more than one sup in a
chassis (only one can handle the control plane though). If a failure were to
occur, say all the VSLs go down, the primary switch would continue
forwarding whereas the other switch would shut down all of its non VSL
ports. This action allows the control and forwarding plane to be stable. As
to what this does to redundancy, you need to make sure you have links to
both as much as possible. I prefer the use of Fast Hello over the others as
it is quicker and does not rely on exterior devices to help the core decide
what to do.

Some would argue that this approach was a sloppy attempt to do what the
Nexus series does with VPCs.

Links:

http://www.cisco.com/web/DK/assets/docs/presentations/VSS_0109.pdf

http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/VSS30dg/VSS-dg_c
h3.html

Quad VSS Sups:

Virtual Switching System (VSS) Quad-Supervisor Uplink Forwarding

Cisco IOS Software Release 12.2(33)SXI4 introduces support for
dual-supervisors in each of the active and standby VSS chassis, together
forming a quad-supervisor VSS system. These secondary supervisors can also
be used to forward traffic on the uplink ports thereby enabling all four
supervisors in a VSS system to actively forward traffic under normal
conditions. Furthermore, the additional supervisors can act as standby
supervisors within each chassis to provide resilient network connectivity to
single-homed devices and maximum bandwidth availability to both upstream and
downstream connected devices

Nexus vPCs:

http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_2/nx-os/interfaces/
configuration/guide/if_vPC.html

Travis

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of JB
Poplawski
Sent: Monday, May 02, 2011 8:35 PM
To: Kiran Parashare
Cc: Ahmed; Cisco certification; Cisco certification
Subject: Re: Design issue

You're losing me on the module failing. You lose the SUP on one of your
switches and you lose that switch. If you have a port channel and lose a
port, the other one should work. If you lose connectivity to both cores
non-VSS... I'm not really sure. If the core is tied together with trunked
switches, one core would "find it's way back to root" via BPDUs riding an
access switch. If you're running VSS, it's recommended to run Dual Active
Detection, in which case VSS (port
channel) link would go down, the ports on one of the switches would all get
set to admin down.

Note, there's a lot smarter dudes on this forum than me, I just happened to
be one to stick my neck out and offer some advice.
Obviously, no one knows your environment better than you, white board it out
and try and break it.

Cheers!
JB

On Mon, May 2, 2011 at 10:24 PM, Kiran Parashare <kiran.ccie_at_gmail.com>
wrote:
> Hi,
>
> What if one of the module fail which has connection between core1-core2.
> Still the server redundacy works ?
>
> HTH

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Received on Mon May 02 2011 - 23:07:03 ART