CCNA Exam 200-125: Configuring IP Address for Layer 3 EtherChannel

Configuring IP Address for Layer 3 EtherChannel

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A network administrator creates a layer 3 EtherChannel, bundling four interfaces into channel group 1. On what interface is the IP address configured?



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A. B. C. D.



In a Layer 3 EtherChannel, the IP address is typically assigned to the port-channel interface, which is the logical interface representing the bundle of physical interfaces. Therefore, the correct answer is A. the port-channel 1 interface.

When configuring a Layer 3 EtherChannel, the administrator needs to select the protocol that will be used for routing between the EtherChannel and other devices. For example, the protocol could be Routing Information Protocol (RIP), Open Shortest Path First (OSPF), or Border Gateway Protocol (BGP). Once the protocol is selected, the administrator needs to configure the IP address and subnet mask on the port-channel interface.

The port-channel interface is created automatically when the EtherChannel is configured. The administrator can assign the channel group number (in this case, 1) and the protocol that will be used for Layer 3 forwarding. Then, the administrator needs to add the physical interfaces to the channel group by specifying the channel group number and the interface type and number. For example, the following commands would create a Layer 3 EtherChannel with four Gigabit Ethernet interfaces:

interface Port-channel1 ip address ! interface GigabitEthernet1/0/1 channel-group 1 mode on ! interface GigabitEthernet1/0/2 channel-group 1 mode on ! interface GigabitEthernet1/0/3 channel-group 1 mode on ! interface GigabitEthernet1/0/4 channel-group 1 mode on

In this example, the IP address with a subnet mask of is assigned to the port-channel1 interface, which represents the bundle of Gigabit Ethernet interfaces 1/0/1 to 1/0/4. The mode "on" is used to create an EtherChannel without negotiation, meaning that all interfaces in the channel group will use the same configuration parameters.

Note that it is also possible to assign IP addresses to individual member interfaces in a Layer 3 EtherChannel, but this is not recommended as it can lead to asymmetric routing and other issues. Therefore, answers C and D (all member interfaces or the lowest number member interface) are incorrect. The highest number member interface (answer B) is not relevant for IP addressing purposes.