Understanding How Etherchannel Guard Works - Cisco 7604 Configuration Manual

Ios software configuration guide

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Understanding How EtherChannel Guard Works

Figure 21-4 BackboneFast Example After Indirect Link Failure

If a new network device is introduced into a shared-medium topology as shown in

BackboneFast is not activated because the inferior BPDUs did not come from the recognized designated

bridge (Switch B). The new network device begins sending inferior BPDUs that indicate that it is the

root bridge. However, the other network devices ignore these inferior BPDUs and the new network

device learns that Switch B is the designated bridge to Switch A, the root bridge.

Figure 21-5 Adding a Network Device in a Shared-Medium Topology

Understanding How EtherChannel Guard Works

EtherChannel guard detects a misconfigured EtherChannel where interfaces on the Cisco 7600 series

router are configured as an EtherChannel while interfaces on the other device are not, or not all the

interfaces on the other device are in the same EtherChannel.

In response to misconfiguration detected on the other device, EtherChannel guard puts interfaces on the

Cisco 7600 series router into the errdisabled state.

Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX

Link failure

BackboneFast transitions port

through listening and learning

states to forwarding state

Blocked port

(Designated Bridge)

Added switch

Configuring Optional STP Features

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