Cisco Systems 3560 사용자 설명서
35-5
Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 35 Configuring EtherChannels and Link-State Tracking
Understanding EtherChannels
Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if
ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not
generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents
that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to
attach the port to a channel group, and to use the port for transmission.
ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not
generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents
that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to
attach the port to a channel group, and to use the port for transmission.
PAgP Interaction with Virtual Switches and Dual-Active Detection
A virtual switch can be two or more Catalyst 6500 core switches connected by virtual switch links
(VSLs) that carry control and data traffic between them. One of the switches is in active mode. The
others are in standby mode. For redundancy, remote switches, such as Catalyst 3650 switches, are
connected to the virtual switch by remote satellite links (RSLs).
(VSLs) that carry control and data traffic between them. One of the switches is in active mode. The
others are in standby mode. For redundancy, remote switches, such as Catalyst 3650 switches, are
connected to the virtual switch by remote satellite links (RSLs).
If the VSL between two switches fails, one switch does not know the status of the other. Both switches
could change to the active mode, causing a dual-active situation in the network with duplicate
configurations (including duplicate IP addresses and bridge identifiers). The network might go down.
could change to the active mode, causing a dual-active situation in the network with duplicate
configurations (including duplicate IP addresses and bridge identifiers). The network might go down.
To prevent a dual-active situation, the core switches send PAgP protocol data units (PDUs) through the
RSLs to the remote switches. The PAgP PDUs identify the active switch, and the remote switches
forward the PDUs to core switches so that the core switches are in sync. If the active switch fails or
resets, the standby switch takes over as the active switch. If the VSL goes down, one core switch knows
the status of the other and does not change state.
RSLs to the remote switches. The PAgP PDUs identify the active switch, and the remote switches
forward the PDUs to core switches so that the core switches are in sync. If the active switch fails or
resets, the standby switch takes over as the active switch. If the VSL goes down, one core switch knows
the status of the other and does not change state.
PAgP Interaction with Other Features
The Dynamic Trunking Protocol (DTP) and the Cisco Discovery Protocol (CDP) send and receive
packets over the physical ports in the EtherChannel. Trunk ports send and receive PAgP protocol data
units (PDUs) on the lowest numbered VLAN.
packets over the physical ports in the EtherChannel. Trunk ports send and receive PAgP protocol data
units (PDUs) on the lowest numbered VLAN.
In Layer 2 EtherChannels, the first port in the channel that comes up provides its MAC address to the
EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides
its MAC address to the EtherChannel.
EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides
its MAC address to the EtherChannel.
PAgP sends and receives PAgP PDUs only from ports that are up and have PAgP enabled for the auto
or desirable mode.
or desirable mode.
Link Aggregation Control Protocol
The LACP is defined in IEEE 802.3ad and enables Cisco switches to manage Ethernet channels between
switches that conform to the IEEE 802.3ad protocol. LACP facilitates the automatic creation of
EtherChannels by exchanging LACP packets between Ethernet ports.
switches that conform to the IEEE 802.3ad protocol. LACP facilitates the automatic creation of
EtherChannels by exchanging LACP packets between Ethernet ports.
By using LACP, the switch learns the identity of partners capable of supporting LACP and the
capabilities of each port. It then dynamically groups similarly configured ports into a single logical link
(channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative,
and port parameter constraints. For example, LACP groups the ports with the same speed, duplex mode,
native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel,
LACP adds the group to the spanning tree as a single switch port.
capabilities of each port. It then dynamically groups similarly configured ports into a single logical link
(channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative,
and port parameter constraints. For example, LACP groups the ports with the same speed, duplex mode,
native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel,
LACP adds the group to the spanning tree as a single switch port.