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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 43 Configuring Link State Tracking
Link State Tracking
Figure 43-1 on page 43-3 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. 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 43-1 ensures that the network traffic flow is balanced as follows:
• For links to switches and other network devices
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Server 1 and server 2 use switch A for primary links and switch B for secondary links.
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Server 3 and server 4 use switch B for primary links and switch A for secondary links.
• Link state group 1 on switch A
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Switch A provides primary links to server 1 and server 2 through link s tate group 1. Port 1 is
connected to server 1, and port 2 is connected to server 2. Port 1 and port 2 a re the downstream
interfaces in link state group 1.
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Port 5 and port 6 are connected to distribution switch 1 throug h 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
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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.
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Port 7 and port 8 are connected to distribution switch 2 throug h 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
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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.
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Port 5 and port 6 are connected to distribution switch 2 throug h 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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Switch B provides secondary 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.
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Port 7 and port 8 are connected to distribution switch 1 through li nk state group 1. Port 7 and
port 8 are the upstream interfaces in link state group 1.
In a link state group, the upstream ports can become unavailable or lose connectivity because the
distribution switch or router fails, the cables are disconnected, or the link is lost. These are the
interactions between the downstream and upstream interfaces when link state tracking is enabled:
• If any of the upstream interfaces are in the link-up state, th e downstream interfaces can change to or
remain in the link-up state.
• If all of the upstream interfaces become unavailable, link state tracking automatically puts the
downstream interfaces in the error-disabled state. Connectivity to and from the servers is
automatically changed from the primary server interface to the secondary server interface.
As an example of a connectivity change from link state group 1 to link state group 2 on switch A,
see Figure 43-1 on page 43-3. If the upstream link for port 6 is lost, the link states of downstream
ports 1 and 2 do not change. However, if the link for upstream port 5 is also lost, the link state of the