Multichassis Etherchannel Restrictions And Guidelines - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 5 Configuring Virtual Switching Systems
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Multichassis EtherChannel Restrictions and Guidelines

When configuring MECs, note the following guidelines and restrictions:
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There is no restriction to configure oversubscribed linecard ports as VSL. The responsibility of
bandwidth availability for a given network requirement lies with the network operator.
VSL portchannel must have more than one port in the channel, preferably distributed on more than
one module. If the VSL consists of only one link, its failure causes a Dual-Active operation of the
VSS. Also, all VSL links configured on one module may cause a Dual-Active operation, if the
module goes down..
Classification and marking based on 'qos-group' in a QoS policy-map is not supported in VSS.
The following older gneration linecards (WS-X42xy to WS-X45xy) are supported with the VSS
feature:
WS-X4148-RJ
–
WS-X4148-RJ
–
WS-X4148-FX-MT
–
WS-X4306-GB
–
WS-X4548-RJ45V+
–
– WS-X4448-GB-SFP
– WS-X4248-FE-SFP
– WS-X4248-RJ45V
Please remove all other linecards from your system when converting from standalone to VSS mode.
Do not attach a QoS policy with the maximum queue-limit (8184) to a large number of targets in a
VSS system. This will cause continuous reloads on the standby supervisor engine.
When an aymmetric virtual switch (i.e. a VSS comprising of chassis with different slot capacities)
boots initially after conversion from standalone mode, the entPhysicalDescr object for the standby
chassis does not hold the correct value. The entPhysicalDescr objects for both the active and standby
chassis will match and hold the value for the active chassis.
After the running configuration is saved and a shelf reload occurs, this behaviour is not observed -
the entPhysicalDescr objects for both chassis accurately reflects the correct chassis types.
Port Security over EtherChannels is not supported.
All links in an MEC must terminate locally on the VSS Active or VSS Standby switch of the same
virtual domain.
An MEC can be connected to another MEC on a different VSS domain.
Policers applied on an MEC are applied on two switches independently; if a policer is applied for
100 Mbps of conforming action, it will apply 100Mbps on both switches, resulting in a total
conforming rate of 200 Mbps. To mitigate this, you can reduce the policer rate. In a more restrictive
case, a rate of 50 Mbps might be necessary to achieve a maximum of 100Mbps. In a more liberal
case, where conforming action of 200 Mbps is not a problem, policing rate could be kept to
100Mbps.
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
VSS Configuration Guidelines and Restrictions
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