Etherchannel

Question 1

What are two other names for Etherchannel?

Answer 1

Port Channel
LAG (Link Aggregation Group)

Question 2

How does Etherchannel load balance?

Answer 2

It uses the same link for communication between a source and a destination. Communication is not broken up over multiple links.

Question 3

What inputs can you use to alter which link Etherchannel uses for a specified source or destination?

Answer 3

Source MAC / IP
Dest MAC / IP
Source + Dest MAC / IP
*some switches can also do layer 4 load balancing

Question 4

What command is used to view the load balancing config?

Answer 4

SW1#show etherchannel load-balance

Question 5

What global config command is used to alter the load balancing config to source-destination MAC?

Answer 5

SW1(config)# port-channel load-balance src-dst-mac

Question 6

What are the 3 kinds of Etherchannel?

Answer 6

1. PAgP (Cisco proprietary)
2. LACP (IEEE 802.3ad)
3. Static Etherchannel

Question 7

What is the maximum number of ACTIVE links that can be used in Etherchannel?

Answer 7

8. Actually you can configure 16 in some cases but only 8 will be active.

Question 8

What command is used to create an LACP Etherchannel group?

Answer 8

SW1(config-if-range)# channel-group 1 mode active / passive

Question 9

What command is used to create an PAgP Etherchannel group?

Answer 9

SW1(config-if-range)# channel-group 1 mode desireable / auto

Question 10

What command is used to create a static Etherchannel group?

Answer 10

SW1(config-if-range)#
channel-group 1 mode on

Question 11

Will an LACP Etherchannel be formed using the below configurations?
1.passive + passive
2. active + passive
3. active + active

Answer 11

1. No
2. Yes
3. Yes

Question 12

Will a PAgP Etherchannel be formed using the below configurations?
1. auto + auto
2. desireable + auto
3. desireable + desireable

Answer 12

1. No
2. Yes
3. Yes

Question 13

Do channel-group numbers need to match across switches?

Answer 13

No. Channel group 1 can connect to channel group 3 on another switch.

Question 14

What command is used to manually change an Etherchannel’s protocol?

Answer 14

SW1(config-if-range)#
channel-protocol lacp / pagp

Question 15

What two commands are used to configure a port channel to be a trunk port?

Answer 15

SW1(config-if)#
switchport trunk encapsulation dot1q

SW1(config-if)#
switchport mode trunk

Question 16

What attributes need to match in order to create an Etherchannel group?

Answer 16

1. Duplex
2. Speed
   Switchport mode (access/trunk)
3. VLAN

Question 17

What command is used to view the active ports used in a port-channel?

Answer 17

SW1#
show etherchannel summary

Question 18

What command is used to view the protocol used in a port-channel?

Answer 18

SW1#
show etherchannel summary

Question 19

What command is used to view the number of port-channels in use on the switch?

Answer 19

SW1#
show etherchannel summary

Question 20

What do the S and U flags mean when listed next to the port channel in the summary output?

Answer 20

S (stands for switch) means Layer 2.
U means in use

NB: R would be Layer 3 (Router)

Question 21

What does a lower case s flag mean when listed next to one of the interfaces in the port-channel summary output?

Answer 21

s (suspended) - not active. The interface has been misconfigured, eg. configured to be an access port instead of a trunk port.

Question 22

What is another command you can use to see a summary of the Etherchannel configuration?

Answer 22

SW1# show etherchannel port-channel

Question 23

What command would you use prior to creating the port-channel group if you wanted to configure a layer 3 routed Etherchannel?

Answer 23

SW1(config-if-range)# no switchport

Question 24

What command do you use to assign a ip address 10.1.1.2/24 to po1?

Answer 24

SW1(config)# int po1
SW1(config-if)# ip address 10.1.1.2 255.255.255.0