Dear Waleed,   Cisco recommendations:   VSL Restrictions: • For line redundancy, we recommend configuring at least two ports per switch for the VSL. For module redundancy, the two ports can be on different switching modules in each chassis. ... View more

Dear Waleed,   VSL Restrictions: - For line redundancy, we recommend configuring at least two ports per switch for the VSL. - For module redundancy, the two ports can be on different switching modules in each chassis.   Review the below restrictions and recommendations:   General VSS Restrictions: • VSS mode does not support supervisor engine redundancy within a chassis. • If you configure a new value for switch priority, the change takes effect only after you save the configuration file and perform a restart. • Out-of-band MAC address table synchronization among DFC-equipped switching modules (the mac address-table synchronize command) is enabled automatically in VSS mode, which is the recommended configuration. • Because the output of the show running-config command on ICS supervisor engines could be out of sync with the active supervisor engine, ICS supervisor engines do not support the show running-config command. The active and standby supervisor engines support the show running-config command.   VSL Restrictions: - For line redundancy, we recommend configuring at least two ports per switch for the VSL. - For module redundancy, the two ports can be on different switching modules in each chassis. • The no platform qos channel-consistency command is automatically applied when you configure the VSL. Do not remove this command. • VSL ports cannot be Mini Protocol Analyzer sources (the monitor ... capture command). Monitor capture sessions cannot be started if a source is the VSL on the port channel of the standby switch. The following message is displayed when a remote VSL port channel on the standby switch is specified and you attempt to start the monitor capture: % remote VSL port is not allowed as capture source The following message is displayed when a scheduled monitor capture start fails because a source is a remote VSL port channel: Packet capture session 1 failed to start. A source port is a remote VSL.   Multichassis EtherChannel (MEC) Restrictions: • All links in an MEC must terminate locally on the active or standby chassis of the same virtual domain. • For an MEC using the LACP control protocol, the minlinks command argument defines the minimum number of physical links in each chassis for the MEC to be operational. • For an MEC using the LACP control protocol, the maxbundle command argument defines the maximum number of links in the MEC across the whole VSS. • MEC supports LACP 1:1 redundancy. For additional information about LACP 1:1 redundancy, refer to the “Information about LACP 1:1 Redundancy” section on page 23-6. • An MEC can be connected to another MEC in a different VSS domain. • Ports on the supervisor engines are not stateful and will experience a reset across switchovers (see the “Switchover Process Restrictions” section on page 7-2). • With an MEC that includes supervisor engine ports configured on a VSS that supports the VSS Quad-Sup SSO (VS4O) feature, be aware of CSCuh51005.   Dual-Active Detection Restrictions: • If Flex Links are configured on the VSS, use PAgP dual-active detection. • For dual-active detection link redundancy, configure at least two ports per switch for dual-active detection. For module redundancy, the two ports can be on different switching modules in each chassis, and should be on different modules than the VSL, if feasible. • When you configure dual-active fast hello mode, all existing configurations are removed automatically from the interface except for these commands: – description – logging event – load-interval – rcv-queue cos-map – rcv-queue queue-limit – rcv-queue random-detect – rcv-queue threshold – wrr-queue bandwidth – wrr-queue cos-map – wrr-queue queue-limit – wrr-queue random-detect – wrr-queue threshold – priority-queue cos-map • Only these configuration commands are available on dual-active detection fast hello ports: – default – description – dual-active – exit – load-interval – logging – no – shutdown     Regards, ... View more