SSO,NSF and VSS

Unanswered Question
Oct 10th, 2010

Hi,

I am working on VSS  and  I am trying to configure the VSS and i read that I need to enable sso as well as nsf and under routing protocol i need to configure nsf command ( router config mode )

can anybody explain about what is sso and nsf why is it required to enable before configuring vss

is it corelated with vss.

I am looking for perticular answer instead of reffering any cisco document for my understanding.

Please help me to understand these three concept.

and " vsl is used to transfer the control information in vss and to minimize we have MEC to carry data information so ingress and egress data transfer will happen on the same switch instead of using VSL if possible" but i get stuck-up with control information concept ............ what is it all about ?

can anybody give example of control information?

I have this problem too.
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Calin Chiorean Sun, 10/10/2010 - 13:37

Hello!

Short answer

SSO = Stateful switchover , establish a relation of active / passive between 2 supervisor engines in a chassis to provide uninterrupted L2 functionality in case of a hardware failure. Imagine that you have 2 SUP in one chassis and one of them is the active one taking care of all operation, while the second one has the same configuration, but it is in standby mode. In case the the first SUP fails, the standby one take care of all operations without any interruption

NFS = Non-stop forwarding, works together with SSO, but this protocol offer support for L3 uninterrupted operations. Protocol like BGP, OSPF are NFS capable, able to detect a failure and react to have no operation interruption.

More about SSO+NFS here (operation and configuration details on a C6500, but the basics are the same on all platforms):

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/nsfsso.html#wp1097378

Now, VSS rely on SSO+NFS to offer High Availability services:

Q. What high-availability mechanisms are available with a VSS?
A. A VSS uses interchassis NSF/SSO as the primary mechanism for high availability between the two chassis. One virtual switch member chassis will act as the active virtual switch member, while the other member will be in hot standby state for the control plane. Note that the data planes of both chassis are active and hence forward traffic at full combined capacity of 1440 Gbps. When one of the virtual switch members fails, there is no reconvergence of protocols in the network. The access layer or core layer switches continues to forward traffic because they only detect a link failure in an EtherChannel bundle and hence do not need to reconverge any protocols. No disruption occurs to the traffic flowing through the VSS. The VSS mechanism during switch failure is far superior when comparison with the traditional model where one switch failure results indeterminist convergence of multiple control protocols like STP, HSRP and routing protocol.
Cheers,
Calin

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Posted October 10, 2010 at 2:14 AM
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