38-18
Cisco IE 3000 Switch Software Configuration Guide
OL-13018-03
Chapter 38 Configuring EtherChannels and Link-State Tracking
Understanding Link-State Tracking
You can clear PAgP channel-group information and traffic counters by using the clear pagp
{channel-group-number counters | counters} privileged EXEC command.
You can clear LACP channel-group information and traffic counters by using the clear lacp
{channel-group-number counters | counters} privileged EXEC command.
For detailed information about the fields in the displays, see the command reference for this release.
Understanding Link-State Tracking
Link-state tracking, also known as trunk failover, is a feature that binds the link state of multiple
interfaces. For example, link-state tracking provides redundancy in the network when used with server
NIC adapter teaming. When the server network adapters are configured in a primary or secondary
relationship known as teaming, if the link is lost on the primary interface, connectivity is transparently
changed to the secondary interface.
Figure 38-4 on page 38-20 shows a network configured with link-state tracking. To enable link-state
tracking, create a link-state group, and specify the interfaces that are assigned to the link-state group. An
interface can be an aggregation of ports (an EtherChannel) or a single physical port in access or trunk
mode. In a link-state group, these interfaces are bundled together. The downstream interfaces are bound
to the upstream interfaces. Interfaces connected to servers are referred to as downstream interfaces, and
interfaces connected to distribution switches and network devices are referred to as upstream interfaces.
The configuration in Figure 38-4 ensures that the network traffic flow is balanced as follows:
• For links to switches and other network devices
–
Server 1 and server 2 use switch A for primary links and switch B for secondary links.
–
Server 3 and server 4 use switch B for primary links and switch A for secondary links.
• Link-state group 1 on switch A
–
Switch A provides primary links to server 1 and server 2 through link-state group 1. Port 1 is
connected to server
1, and port 2 is connected to server 2. Port 1 and port 2 are the downstream
interfaces in link-state group 1.
–
Port 5 and port 6 are connected to distribution switch 1 through link-state group 1. Port 5 and
port 6 are the upstream interfaces in link-state group 1.
• Link-state group 2 on switch A
–
Switch A provides secondary links to server 3 and server 4 through link-state group 2. Port 3 is
connected to server 3, and port 4 is connected to server 4. Port 3 and port 4 are the downstream
interfaces in link-state group 2.
–
Port 7 and port 8 are connected to distribution switch 2 through link-state group 2. Port 7 and
port 8 are the upstream interfaces in link-state group 2.
• Link-state group 2 on switch B
–
Switch B provides primary links to server 3 and server 4 through link-state group 2. Port 3 is
connected to server 3, and port 4 is connected to server 4. Port 3 and port 4 are the downstream
interfaces in link-state group 2.
–
Port 5 and port 6 are connected to distribution switch 2 through link-state group 2. Port 5 and
port 6 are the upstream interfaces in link-state group 2.
• Link-state group 1 on switch B
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