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Doubt in Etherchannel?

Dear All,

I am having doubt in Etherchannel.Can any one give me the solution for that?

1.What is the difference between Layer 2 Etherchannel and Layer 3 Etherchannel?

2.What is the difference between Pagp and Lacp other than Standared?

3.What is the use of Etherchannel in Layer 2 switches?

Thanks in advance

Senthil

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1 ACCEPTED SOLUTION

Accepted Solutions

Re: Doubt in Etherchannel?

Dear All,

I am having doubt in Etherchannel.Can any one give me the solution for that?

1.What is the difference between Layer 2 Etherchannel and Layer 3 Etherchannel?

2.What is the difference between Pagp and Lacp other than Standared?

3.What is the use of Etherchannel in Layer 2 switches?

Thanks in advance

Senthil

Hi Senthil,

Answer to question 2:- PagP is cisco proprietary, LACP is standards based. So using one or the other depends on what brand hardware you have.There's not that much difference between the 2 except that LACP, beyond identifying neighbours and port group capabilities, also assigns roles to the EtherChannel endpoints by identifying the switch with the lowest system priority. The switch with the lowest system priority (2 byte priority value and 6 byte switch MAC address) is allowed to make decisions about what ports actively are used in the EtherChannel at any given time.

Answer to Question 1:-With the L3 etherchannel, the switch would use a logical L3 interface called a "portchannel", and that interface would get an IP address.

Answer to Question 3:-

There is one situation where STP works against us just a bit while it prevents switching loops, and that is the situation where two switches have multiple physical connections.You would think that if you have two separate physical connections between two switches, twice as much data could be sent from one switch to the other than if there was only one connection. STP doesn't allow this by default, however in an effort to prevent switching loops from forming, one of the paths will be blocked.


While STP is helping us by preventing switching loops, STP is also hurting us by preventing us from using a perfectly valid path between SW1 and SW2. We could literally double the bandwidth available between the two switches if we could use that path that is currently being blocked. The secret to using the currently blocked path is configuring an Etherchannel. An Etherchannel is simply a logical bundling of 2 - 8 physical connections between two Cisco switches. The beauty of an Etherchannel is that STP sees the Etherchannel as one connection. If any of the physical connections inside the Etherchannel go down, STP does not see this, and STP will not recalculate. While traffic flow between the two switches will obviously be slowed, the delay in transmission caused by an STP recalculation is avoided. An Etherchannel also allows us to use multiple physical connections at one time.

Hope to help !!

Ganesh.H

Remember to rate the helpful post

2 REPLIES

Re: Doubt in Etherchannel?

Dear All,

I am having doubt in Etherchannel.Can any one give me the solution for that?

1.What is the difference between Layer 2 Etherchannel and Layer 3 Etherchannel?

2.What is the difference between Pagp and Lacp other than Standared?

3.What is the use of Etherchannel in Layer 2 switches?

Thanks in advance

Senthil

Hi Senthil,

Answer to question 2:- PagP is cisco proprietary, LACP is standards based. So using one or the other depends on what brand hardware you have.There's not that much difference between the 2 except that LACP, beyond identifying neighbours and port group capabilities, also assigns roles to the EtherChannel endpoints by identifying the switch with the lowest system priority. The switch with the lowest system priority (2 byte priority value and 6 byte switch MAC address) is allowed to make decisions about what ports actively are used in the EtherChannel at any given time.

Answer to Question 1:-With the L3 etherchannel, the switch would use a logical L3 interface called a "portchannel", and that interface would get an IP address.

Answer to Question 3:-

There is one situation where STP works against us just a bit while it prevents switching loops, and that is the situation where two switches have multiple physical connections.You would think that if you have two separate physical connections between two switches, twice as much data could be sent from one switch to the other than if there was only one connection. STP doesn't allow this by default, however in an effort to prevent switching loops from forming, one of the paths will be blocked.


While STP is helping us by preventing switching loops, STP is also hurting us by preventing us from using a perfectly valid path between SW1 and SW2. We could literally double the bandwidth available between the two switches if we could use that path that is currently being blocked. The secret to using the currently blocked path is configuring an Etherchannel. An Etherchannel is simply a logical bundling of 2 - 8 physical connections between two Cisco switches. The beauty of an Etherchannel is that STP sees the Etherchannel as one connection. If any of the physical connections inside the Etherchannel go down, STP does not see this, and STP will not recalculate. While traffic flow between the two switches will obviously be slowed, the delay in transmission caused by an STP recalculation is avoided. An Etherchannel also allows us to use multiple physical connections at one time.

Hope to help !!

Ganesh.H

Remember to rate the helpful post

New Member

Re: Doubt in Etherchannel?

Dear Ganesh,

                   Thanks for your reply. Your guidelines is very informative and very useful..Now i am clear..

Tks&Rgds

Senthil

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