TOP 10 ETHERCHANNEL Interview Questions & Answers

Question 1 – What is Etherchannel and why do we need it ?

Etherchannel is a method of logical bundling of multiple physical links into a single logical channel.

Advantage

More Bandwidth

Redundancy

Also known as Port Aggregation

Question 2 –How many links we can bundle in to one Etherchannel?

Depends upon the negotiation protocol

Incase of LACP - We can combine / bundle upto 16 links in to one Etherchannel   8 active + 8 standby

Incase of PAgP- We can combine / bundle upto 8 links in to one Etherchannel

Question 3 –How many Etherchannels can be configured on a Switch?

The maximum number of supported EtherChannels on a single switch is platform-dependent, though most support up to 64 or 128 EtherChannels.

Catalyst 3550XL switch supports max. 64 ECs.

Catalyst 6500 switch supports max. 128 ECs.

Question 4 –What are the requirements for Etherchannel ?

All the ports must have same Speed & Duplex.

All the ports must be in same switchport mode (Access / Trunk)

If the ports are in Access mode then they should be member of same VLAN.

If the ports are in Trunk mode then they should same Native Vlan , Allowed Vlan and Trunking encapsulation Protocol.

None of the ports in the bundle can be a SPAN port .

Question 5 –Etherchannel is Layer 2 or Layer 3?

We configure both Layer 2 & Layer 3 Etherchannel depending upon the requirement .

Layer 2 Etherchannel – switchport & No IP Address.

Layer 3 Etherchannel – no switchport & Etherchannel will have IP Address.

Question 6 –What are different Etherchannel Modes?

There are multiple modes in Etherchannel :-

On – Manually configured Etherchannel (negotiation is disable)

LACP – Industry Standard

Active -The interface which is configured in this mode will actively try to form the Etherchannel.

Passive - The interface which is configured in this mode will passively try to form the Etherchannel.

PAgP – Cisco Proprietary

Desirable - The interface which is configured in the mode will actively try to form the Etherchannel.

Auto - The interface which is configured in the mode will passively try to form the Etherchannel.

Question 7 –How to configure Etherchannel mode between 2 switches ?

Switch(config)#int range fa0/1-4

Switch(config-if)#channel-group 10 mode <on/auto/desirable/passive/active>

Question 8 –How to troubleshoot the etherchannel when interfaces are configured in LACP Passive mode on both the switches?

If the Interfaces are configured in Passive mode on both the switches then Etherchannel won’t come up .

To troubleshoot we need to configure the interfaces on one switch as Active.                                                                                                                     

Question 9 –What are the load balancing methods supported by Etherchannel?

EtherChannel utilizes a load-balancing algorithm to determine the port to send the traffic out, based on one of several criteria:

 Source IP address - src-ip

 Destination IP address - dst-ip

 Source and destination IP address - src-dst-ip

 Source MAC address - src-mac

 Destination MAC address - dst-mac

 Source and Destination MAC address - src-dst-mac

 Source TCP/UDP port number - src-port

 Destination TCP/UDP port number - dst-port

Source and destination port number - src-dst-port

Question 10 –What is Port Priority value in LACP Etherchannel?

Port Priority is an additional configuration option in LACP.

It is used to determine which ports can become active in Etherchannel and which ports to become standby when there is a limitation that prevents all compatible ports from aggregating.

Values ranges from <1 – 65535 >

Lower value means Higher Priority

Thanks for Reading !!!!

amartechstuff

Switch(config-if)# lacp port-priority “PRIORITY”