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
