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Nexus Switching 2nd Edition

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Click here to view code image<br />

Congo(config)# int ethernet 2/21<br />

Congo(config-if)# spanning-tree bpdufilter disable<br />

Congo(config-if)#<br />

RootGuard<br />

RootGuard protects the root placement in the bridging domain. If a port configured with<br />

RootGuard receives a superior BPDU, the port is immediately placed into an inconsistent<br />

state. RootGuard is typically implemented in the data center aggregation layer to prevent<br />

misconfigured access switches from becoming the root bridge for the entire data center<br />

aggregation block. RootGuard can be implemented only on a port-by-port basis.<br />

Example 2-49 shows how to enable RootGuard on a specific interface.<br />

Example 2-49. RootGuard Configuration<br />

Click here to view code image<br />

Congo(config)# int ethernet 2/1<br />

Congo(config-if)# spanning-tree guard root<br />

Congo(config-if)#<br />

Now, test RootGuard by changing the priority of a Kenya to a lower value.<br />

Example 2-50 shows RootGuard in action.<br />

Example 2-50. RootGuard Verification<br />

Click here to view code image<br />

Kenya(config)# spanning-tree vlan 1 priority 0<br />

Output from Congo<br />

Congo# 2009 Oct 28 14:50:24 Congo %STP-2-ROOTGUARD_BLOCK:<br />

Root guard blocking port<br />

Ethernet2/1 on VLAN0001.<br />

Congo#<br />

! When we remove the priority comm<strong>and</strong>, port connectivity<br />

is restored.<br />

Kenya(config)# no spanning-tree vlan 1 priority 0<br />

Output from Congo<br />

Congo# 2009 Oct 28 14:51:19 Congo %STP-2-<br />

ROOTGUARD_UNBLOCK: Root guard unblocking<br />

port<br />

Ethernet2/1 on VLAN0001.

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