Module 5 - Implementing Layer 2 Port Aggregation

Question 1

What are 3 port-aggregation L2 protocols?

Answer 1

PAGP

LACP (IEEE standard - 802.3ad)

Static.

LACP is now really the industry standard, great in mixed environments. PAGP is Cisco proprietary.

Question 2

LACP (802.3ad)

Answer 2

802.3ad IEEE standard. Operates in Active/Passive modes.

Automatic negotiation if one side is set to active.

Question 3

Etherchannel Theory?

What is it? Why is it used?

Answer 3

It’s a L2 port-aggregation technology, used at layer 2. It logicially bundles links together and can help remove loops within a network.

It is common to have 2 or 4 links in an etherchannel bundle. 8 - 16 is possible but can take up alot of ports.

It is more a ‘load-sharing’ technology than a loan balancing technology. It is useful as it provides redundancy to connecting devices.

It uses a load sharing algorithm, frames tend to always traverse a particular link.

Question 4

PAGP

Answer 4

Developed by Cisco, common to see in Cisco environments but LACP is now preferred.

Uses modes : desirable or auto

Question 5

Static Etherchannel

Answer 5

Uses only one mode On.

No negotiation like PAGP or LACP.

Question 6

Q.

Which two statements about the EtherChannel technology are true? (Choose two.)

1. EtherChannel provides increased bandwidth by bundling existing Fast Ethernet or Gigabit Ethernet interfaces into a single EtherChannel.
2. STP can block one of the physical links in an EtherChannel to prevent a loop.
3. You can configure multiple EtherChannel links between two switches, using up to a limit of 16 physical ports.
4. EtherChannel does not allow load sharing of traffic among the physical links within the EtherChannel.
5. EtherChannel allows redundancy in case one or more links in the EtherChannel fail.

Answer 6

A.

EtherChannel provides increased bandwidth by bundling existing Fast Ethernet or Gigabit Ethernet interfaces into a single EtherChannel.

EtherChannel allows redundancy in case one or more links in the EtherChannel fail.

Question 7

Channel Mode Interactions

Answer 7

LACP

Active/Active - channel-group formed
Active/Passive - formed
Passive/Passive - not formed

PAGP

Desirable/Desirable - channel formed
Desirable/Auto - channel formed
Auto/Auto (not formed)

Static

On - channel formed

Question 8

Configuring Etherchannel

Answer 8

Make sure that you have an even number of links, that the speed is the same also.

Best practice to configure the channel-group on the interface and the mode. Then create the config on the created port-channel interfaces which will be inherited by the ports.

Note

When Configuring Layer 3 switches for an EtherChannel trunk you must also indicate the encapsulation used with the switchport trunk encapsulation encapsulation command.

Question 9

Q.

Which is NOT a requirement for EtherChannel configuration?

1. interfaces must be the same speed and duplex
2. Interfaces must be physically contiguous
3. Interfaces must have the same VLAN configuration
4. Interfaces must be the same mode

Answer 9

Interfaces must be physically contiguous.

Question 10

Q

Frames are forwarded over an EtherChannel link that is based on the results of a hashing algorithm. Which of the following two options can a switch use to calculate this hash. (Choose two.)

1. Loopback address
2. Destination IP address
3. Router ID
4. Source port number
5. VLAN

Answer 10

A.

Source port number

Destination IP address

Question 11

Troubleshooting Etherchannel

Answer 11

Common issues are speed, duplex, trunking mode or L2/L3 operations. Mistmatched establishment modes… can’t mix PAGP/LACP

You could get issues with suspended interfaces or non functioning port-channel.

Question 12

Q.

What is the correct command for configuring load balancing on an EtherChannel link?

1. Switch(config)# channel-group number load-balance method
2. Switch(config-if)# channel-group number load-balance method
3. Switch(config-if)# port-channel number load-balance method
4. Switch(config)# port-channel load-balance method

Answer 12

A.

Switch(config)# port-channel load-balance method

Question 13

Q.

Which of the following EtherChannel modes does not send or receive any negotiation frames?

1. passive
2. active
3. on
4. desirable
5. auto

Answer 13

A.

On

Question 14

Q.

Which two of the following options correctly defines the characteristics for EtherChannel? (Choose two)

1. High bandwidth
2. low convergence timing
3. Load sharing across links
4. multiple logical ports for RSTP+
5. Server scalability

Answer 14

A.

High bandwidth and load sharing across links.

Question 15

Q.

Place the steps to configure EtherChannel in the correct order.

Step 1

Identify the ports to use on each switch

Step 2

Configure the channel group on the interface

Step 3

Configure the port channel interface

Step 4

Verify connectivity

Answer 15

A.

Step 1 Identify the ports to use on each switch

Step 2 Configure the channel group on the interface

Step 3 Configure the port channel interface

Step 4 Verify connectivity

Question 16

Q.

Which of the following two commands can be used to check the status of the member interfaces and the logical channel interface?

1. show etherchannel load-balance
2. show etherchannel summary
3. show etherchannel traffic
4. show etherchannel groupnumber detail
5. show ip interface brief

Answer 16

A.

Show etherchannel summary

and

Show etherchannel groupnumber detail

Question 17

Q.

Which of these is not a load-balancing option on a Cisco Catalyst switch?

1. src-dst-ip
2. src-dst-mac
3. src-dst-name
4. src-dst-port

Answer 17

A.

src-dst-name

Question 18

Q.

Which two protocol choices do you have when you are implementing an EtherChannel bundle? (Choose two.)

1. LACP
2. PAgP
3. LAPD
4. dot1Q
5. PADP

Answer 18

A.

LACP and PAGP