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EtherChannel Questions 5

November 22nd, 2018 in SWITCH 300-115 Go to comments

Question 1

Explanation

Source MAC address is not correct as this is the MAC address of the router which is always fixed.

Destination MAC address is not correct as this is the MAC address of the server which is always fixed too.

Same for “source and destination MAC address”, it is not suitable either. In general we cannot use any MAC address for load balancing in this topology -> only source IP address is the best choice (as each “customer” has a different source IP address).

Question 2

Question 3

Question 4

Note: This question is same as Q.15 above, but with different answers.

Question 5

Explanation

You can use EtherChannel guard to detect an EtherChannel misconfiguration between the switch and a connected device. A misconfiguration can occur if the switch interfaces are configured in an EtherChannel, but the interfaces on the other device are not. A misconfiguration can also occur if the channel parameters are not the same at both ends of the EtherChannel.

If the switch detects a misconfiguration on the other device, EtherChannel guard places the switch interfaces in the error-disabled state, and displays an error message.

You can enable this feature by using the “spanning-tree etherchannel guard misconfig” global configuration command.

Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/swstpopt.html

Question 6

Question 7

Question 8

Question 9

Question 10

Explanation

According to the exhibit above, Switch1 has been configured with LACP while Switch2 is using Etherchanell static mode (“On”) so there is a protocol mismatch.

Another error in Switch2 is that there is only Fa0/1 joined in the port-channel group 1 but even so the port-channel between two switches can still go up if they are properly configured.

Comments
  1. sky
    December 17th, 2018

    Q6 A and D
    • When configuring Layer 3 EtherChannels, you must manually create the port channel logical
    interface as described in this section, and then put the Layer 3 LAN ports into the channel group (see
    the “Configuring Channel Groups” section on page 12-8).
    • To move an IP address from a Layer 3 LAN port to an EtherChannel, you must delete the IP address
    from the Layer 3 LAN port before configuring it on the port channel logical interface.
    To create a port channel interface for a Layer 3 EtherChannel, perform this task:
    Command Purpose
    Step 1 Router(config)# interface port-channel
    group_number
    Creates the port channel interface.
    Router(config)# no interface port-channel
    group_number
    Deletes the port channel interface.
    Step 2 Router(config-if)# ip address ip_address mask Assigns an IP address and subnet mask to the
    EtherChannel.
    Step 3 Router(config-if)# end Exits configuration mode.
    Step 4 Router# show running-config interface
    port-channel group_number
    Verifies the configuration.
    12-8
    Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide, Release 12.2SXF
    OL-3999-08
    Chapter 12 Configuring EtherChannels
    Configuring EtherChannels
    With Release 12.2(18)SXE and later releases, the group_number can be 1 through 256, up to a maximum
    of 128 port-channel interfaces. With releases earlier than Release 12.2(18)SXE, the group_number can
    be 1 through 256, up to a maximum of 64 port-channel interfaces.
    This example shows how to create port channel interface 1:
    Router# configure terminal
    Router(config)# interface port-channel 1
    Router(config-if)# ip address 172.32.52.10 255.255.255.0
    Router(config-if)# end
    This example shows how to verify the configuration of port channel interface 1:
    Router# show running-config interface port-channel 1
    Building configuration…
    Current configuration:
    !
    interface Port-channel1
    ip address 172.32.52.10 255.255.255.0
    no ip directed-broadcast
    end
    Router#

  2. trueteller
    December 21st, 2018

    @sky
    B and D are correct ones. Refer to https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/15-0_2_se/configuration/guide/3750x_cg/swethchl.html#41054

    “When configuring Layer 3 EtherChannels, you should first manually create the port-channel logical interface by using the interface port-channel global configuration command. Then you put the logical interface into the channel group by using the channel-group interface configuration command.

    Note: To move an IP address from a physical port to an EtherChannel, you must delete the IP address from the physical port before configuring it on the port-channel interface.”

    So you create port-channel, use no switchport, add address and then you go to physical interfaces.

    At physical interface, delete any IP address, use no switchport and add channel-group to port-channel number with protocol that you want to use.

    Thats why A doesn’t match. You add mode and channel-group on physical interface, not to port-channel.

  3. Q 1
    July 28th, 2019

    Based on Figure 40-5 on cisco doc https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_53_se/configuration/guide/3750xscg/swethchl.html

    The router on the figure can be treated as the server stated in the question. From server’s point of view, when it sends traffic out to clients (or users), the traffic is “one to many” pattern, hence, we use destination-based forwarding.

    B. is the only destination-based forwarding method.

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