RE: VSS and PFC3A

Hi.

I agree with you both, a dual active link is a good thing to have in a VSS
setup, but remember that Dual active detection does not work on a Cisco 3750
stack. Most people I have seen are using the 6500 as either core or
distribution with 3750s as either access or distribution switches, and that
makes often things a bit more complicated if they wishes to use dual active
detection.

Best regards
Martin

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
KRATTIGER Lukas
Sent: 4. august 2009 20:13
To: ccie_at_reid.it
Cc: Ram Shummoogum; ccielab_at_groupstudy.com
Subject: AW: VSS and PFC3A

Hi Andy
correct, I certainly do also not recommend deploying VSS without the
"sync-link" but it's not a must.
Your points are all correct.
Cheers
-Lukas

________________________________

Von: Andy Reid [mailto:ccie_at_reid.it]
Gesendet: Di 04.08.2009 18:32
An: KRATTIGER Lukas
Cc: Ram Shummoogum; <ccielab_at_groupstudy.com>
Betreff: Re: VSS and PFC3A

Well Lukas,

I strongly disagree - I certainly do not recommend deploying VSS without the
'sync-link'.
This 'sync-link' is known as VSLP dual-active fast-hello and it uses special
hello messages over a backup Ethernet connection. Dual-active fast-hello is
faster than IP BFD and does not require support from a neighbor switch.
It is one of three mechanisms used by the virtual switching system in order
to detect a dual-active scenario if the VSL fails.
A VSL failure is important to protect against as both chassis become active.
This can obviously have adverse effects on network stability because both
chassis use the same IP addresses, SSH keys, and STP bridge ID.
If a client still wishes to go ahead without the additional link, then I
raise it as a risk which the client accepts before proceeding with the
implementation. The only times this has been raised is when the chassis are
some distance apart and the link has to be leased. At all other times the
link should be implemented as standard if both chassis are within the same
data-center.

regards Andy

KRATTIGER Lukas wrote:

        Hi Andy
        Your so called sync-link is not needed, this will run on the 10G VSL
links.
        There is no requirement to have an additional 1G link between the
chassis.
        A 1g link for dual-active detection would be helpfull but not
required.
        Cheers
        -Lukas
        
        ________________________________
        
        Von: Andy Reid [mailto:ccie_at_reid.it]
        Gesendet: Di 04.08.2009 17:20
        An: KRATTIGER Lukas
        Cc: Ram Shummoogum; ccielab_at_groupstudy.com
        Betreff: Re: AW: AW: VSS and PFC3A
        
        
        
        Hi Ram,
        
        Remember if you have 10GE cards installed it is not possible to
remove
        their DFC's as they come installed as standard, which leaves the
upgrade
        supervisor option. Note that you cannot have two supervisors in the
same
        chassis when switching to VSS mode (at least not at the current SXI
        release). Only one supervisor in each chassis is supported, and each
        must be a VS-S720-10GE-3C or VS-S720-10GE-3CXL. It is not possible
to
        use an older supervisor in each chassis and use 10GE cards (such as
the
        4, 8 or 16 port versions).
        Don't forget that you also need a synchronization link between the
two
        chassis once cut-over - this is usually a 1GE copper link if they
are
        the same room - it does not carry client traffic but information
such as
        keep-alives and state information.
        
        regards Andy
        
        KRATTIGER Lukas wrote:
          

                Hi Ram
                
                
                
                You are correct. The DFC, CFC are on the linecards. There
are also
                limitations according to the daughter cards.
                
                The only VSS compatible Supervisor is the
VS-S720-10GE-3C/XL. It's a
                Sup720 with 2x 10G and PFC3c on it. All other Sups are not
able to do
                VSS.
                
                
                
                I hope this helps.
                
                
                
                Cheers
                
                -Lukas
                
                
                
                Von: Ram Shummoogum [mailto:rshummoo_at_ca.ibm.com]
                Gesendet: Dienstag, 4. August 2009 16:44
                An: KRATTIGER Lukas
                Cc: ccielab_at_groupstudy.com
                Betreff: Re: AW: VSS and PFC3A
                
                
                
                
                
                Thanks for getting back so fast.
                
                When you say remove the PFC3A and replace with CFC or
DFC3c/DFC3cXL: Are
                you referring to the SUP720. I thought CFC and DFC are only
for
                linecards.
                
                For the line cards I am good as they are new and are DFC3C.
                
                Thanks
                
                
                
                
                
                
                "KRATTIGER Lukas" <Lukas.KRATTIGER_at_nextiraone.ch>
<mailto:Lukas.KRATTIGER_at_nextiraone.ch>
                
                08/04/2009 10:38 AM
                
                To
                
                Ram Shummoogum/Quebec/IBM_at_IBMCA, <ccielab_at_groupstudy.com>
<mailto:ccielab_at_groupstudy.com>
                
                cc
                
                
                Subject
                
                AW: VSS and PFC3A
                
                
                
                
                
                
                
                
                Hi Ram
                
                Just remove your PFC3A and replace it with a CFC or buy a
DFC3c/DFC3cXL.
                These are your two options.
                A VSS will never work with distributed forwarding below 3c.
                Just as a side note: The linecards for your VSLs need to
have a
                DFC3c/DFC3cXL on it.
                
                Cheers
                -Lukas
                
                
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Received on Wed Aug 05 2009 - 17:15:52 ART