Guidelines For Configuring Vlans And Trunks; Etherchannel Interaction With Other Features - Cisco WS-C2948G-GE-TX Configuration Manual

EtherChannel Configuration Guidelines and Restrictions

Guidelines for Configuring VLANs and Trunks

This section lists the guidelines and restrictions for configuring VLAN and trunks for EtherChannel:
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EtherChannel Interaction with other Features

This section lists the guidelines and restrictions for EtherChannel's interaction with other features:
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With software release 6.3(1) and later releases, a PAgP-configured EtherChannel is preserved even if it
Note
contains only one port (this situation does not apply to LACP-configured EtherChannels). In software
releases prior to 6.3(1), traffic was disrupted when you removed a 1-port channel from spanning tree and
then added it to spanning tree as an individual port.
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
6-4
the channel but still functions as a nonchannel port. A syslog message is generated when this
condition occurs. Normal LACP behavior is reenabled automatically when the link is set back to full
duplex.
Assign all ports in an EtherChannel to the same VLAN, or configure them as trunk ports.
If you configure the EtherChannel as a trunk, configure the same trunk mode on all the ports in the
EtherChannel. Configuring ports in an EtherChannel in different trunk modes can have unexpected
results.
An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking
EtherChannel. If the allowed range of VLANs is not the same for a port list, the ports do not form
an EtherChannel even when set to the auto or desirable mode with the set port channel command.
Do not configure the ports in an EtherChannel as dynamic VLAN ports. Doing so can adversely
affect switch performance.
Ports with different VLAN costs or VLAN configurations cannot form a channel.
An EtherChannel will not form with ports that have different GARP VLAN Registration Protocol
(GVRP), GARP Multicast Registration Protocol (GMRP), and quality of service (QoS)
configurations.
An EtherChannel will not form with ports where the port security feature is enabled. Do not enable
the port security feature for ports in an EtherChannel.
An EtherChannel will not form if one of the ports is a SPAN destination port.
An EtherChannel will not form if protocol filtering is set differently on the ports.
Cisco Discovery Protocol (CDP) runs on the physical port even after the port is added to a channel.
VLAN Trunking Protocol (VTP) and Dual Ring Protocol (DRiP) run on the channel.
During fast switchover to the standby supervisor engine, all channeling ports are cleared on its
channeling configuration and state, and the links are pulled down temporarily to cause partner ports
to reset. All ports are reset to the nonchanneling state.
Ports with different dot1q port types cannot form a channel.
Ports with different jumbo frame configurations cannot form a channel.
Ports with different dynamic configurations cannot form a channel.
If one port in an EtherChannel is used by IGMP multicast filtering, you must set the EtherChannel
mode for both PAgP and LACP to off. No other mode may be used.
Chapter 6 Configuring Fast EtherChannel and Gigabit EtherChannel
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