Cisco Catalyst 2960-XR Configuration Guide

When two stacks merge that have EtherChannels configured between them, self-looped ports result. Spanning
tree detects this condition and acts accordingly. Any PAgP or LACP configuration on a winning switch stack
is not affected, but the PAgP or LACP configuration on the losing switch stack is lost after the stack reboots.
For a mixed stack containing one or more Catalyst 2960-S switches, we recommend that you configure no
more than six EtherChannels on the stack.
Switch Stacks and PAgP
With PAgP, if the active switch fails or leaves the stack, the standby switch becomes the new active switch.
A spanning-tree reconvergence is not triggered unless there is a change in the EtherChannel bandwidth. The
new active switch synchronizes the configuration of the stack members to that of the active switch. The PAgP
configuration is not affected after an active switch change unless the EtherChannel has ports residing on the
old active switch.
Switch Stacks and LACP
With LACP, the system ID uses the stack MAC address from the active switch, and if the active switch
changes, the LACP system ID can change. If the LACP system ID changes, the entire EtherChannel will flap,
and there will be an STP reconvergence. Use the stack-mac persistent timer command to control whether
or not the stack MAC address changes during a active switch failover.
Default EtherChannel Configuration
The default EtherChannel configuration is described in this table.
Table 17: Default EtherChannel Configuration
Default SettingFeature
None assigned.Channel groups
None defined.Port-channel logical interface
No default.PAgP mode
Aggregate-port learning on all ports.PAgP learn method
128 on all ports.PAgP priority
No default.LACP mode
Aggregate-port learning on all ports.LACP learn method
32768 on all ports.LACP port priority
32768.LACP system priority
LACP system priority and the switch or stack MAC
address.
LACP system ID
Catalyst 2960-XR Switch Layer 2 Configuration Guide, Cisco IOS Release 15.0(2)EX1
OL-29424-01 119
Configuring EtherChannels
Default EtherChannel Configuration

Cisco Catalyst 2960-XR Specifications

General

Stacking Bandwidth	80 Gbps
Layer Support	Layer 2 and Layer 3
Jumbo Frame Support	9198 bytes
RAM	512 MB
Input Voltage	100-240V AC
Model	Catalyst 2960-XR
Uplink Interfaces	4 x 1G SFP or 2 x 10G SFP+
Downlink Interfaces	24 or 48 x Gigabit Ethernet ports
Power Supply	Internal
MAC Address Table Size	16, 000 entries
PoE	Available on PoE models
Weight	4.5 kg
Features	energy efficiency
Stacking	Up to 8 switches
Operating Temperature	0 to 45°C