4507 with four WSX4448GB-RJ45 - best practice to do etherchannel

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Apr 19th, 2007
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Dears,


I have some questions about how I could create EtherChannel on my hardware profile and keep high performance with redundance

, and your assistance it will be very useful for me:



The Hardware Profile is:



There are two supervisor (P/N WS-X4516-10GE) that connect on slots one and two respectively, and five switching module (P/N

WS-X4448-GB-RJ45) that connect on slots 3,4,5,6 and 7, as below.



I verified on the configuration guide in CCO, where show the following form to connect ports on the switching module

WS-X4448-GB-RJ45.


The switching module WS-X4448-GB-RJ45 have 48 oversubscribed ports in six groups of eight ports each:


Group1/Ports - 1, 2, 3, 4, 5, 6, 7, 8

Group2/Ports - 9, 10, 11, 12, 13, 14, 15, 16

Group3/Ports - 17, 18, 19, 20, 21, 22, 23, 24

Group4/Ports - 25, 26, 27, 28, 29, 30, 31, 32

Group5/Ports - 33, 34, 35, 36, 37, 38, 39, 40

Group6/Ports - 41, 42, 43, 44, 45, 46, 47, 48



The eight ports within each group use common circuitry that effectively multiplexes the group into a single, nonblocking,

full-duplex Gigabit Ethernet connection to the internal switch fabric. For each group of eight ports, frames received are

buffered and sent to the common Gigabit Ethernet link to the internal switch fabric. If the amount of data received for a

port begins to exceed buffer capacity, flow control sends pause frames to the remote port to temporarily stop traffic and

prevent frame loss. When the Gigabit Ethernet switching module is not fully utilized, you can connect balancing port connections across port groupings to maximize available bandwidth. For example, with the WS-X4448-GB-RJ45 10/100/1000 switching module, you can connect ports from different groups such as ports 4, 12, 20, or 30 (in any order) before you connect ports from the same group, such as ports 1, 2, 3, 4, 5, 6, 7 and 8.



Question 1 - Assuming that I need create two EtherChannel interface each one with four ports and connect the ports in

switching module on the following scenarios:


>>> Scenario One (Same Module)


If I connect all ports on the same oversubscribed group, for example:


interface Port-channel1


Ge3/1 (module3/group1)

Ge3/2 (module3/group1)

Ge3/3 (module3/group1)

Ge3/4 (module3/group1)


interface Port-channel2


Ge3/9 (module3/group2)

Ge3/10 (module3/group2)

Ge3/11 (module3/group2)

Ge3/12 (module3/group2)



>>> Scenario Two (Same Module)


If I connect the ports on different oversubscribed groups, for example:



interface Port-channel1


Ge3/1 (module3/group1)

Ge3/9 (module3/group2)

Ge3/17 (module3/group3)

Ge3/25 (module3/group4)


interface Port-channel2


Ge3/2 (module3/group1)

Ge3/10 (module3/group2)

Ge3/18 (module3/group3)

Ge3/26 (module3/group4)



>>> Scenario Tree (Differents Module with Redundance)


If I connect the ports on different oversubscribed groups and modules, for example:


interface Port-channel1


Ge3/1 (module3/group1)

Ge4/1 (module4/group1)

Ge5/1 (module5/group1)

Ge6/1 (module6/group1)


interface Port-channel2


Ge3/9 (module3/group2)

Ge4/9 (module4/group2)

Ge5/9 (module5/group2)

Ge6/9 (module6/group2)



It will have improves or degradation in the performance connecting in such a way on each scenario? Which the scenarios that the Cisco recommends as the best-practice to connect the ports that belong to each EtherChannel interface?

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leighharrison Fri, 04/20/2007 - 03:18
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Hi there,


Whenever I build up etherchannel links, I always make sure that I'm covering my bases for redundancy. This means that I put a single port channel over different modules and wherever possible different groups.


This ensures that I'll not loose a port channel if one of the switch blades dies or if one of the group asics breaks (which I've never actually had happen to me).


It is also important to know how the load balancing takes place with regard to your buffer worries. The load balancing is per flow rather than per packet, so the switching logic would send the next flow down the least busy channel in the group. Also, you can only group interfaces that have the same capabilities. Try the command "show interface capabilities" and ensure that they all match up.


However, I'm afraid that with the 4500 chassis, there are physical limitations to the backplane and depending on how much traffic will be shifted over the links and punted to the supervisor, it might be worth considering a trade up to a 6500.


Hope that helps,

LH


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ulisses_2rdatatel Fri, 04/20/2007 - 10:52
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Thanks for your reply Leigh Harrison! Very useful for me.


I also think thus, to obtain load balancing and redundancy. But as well as you, I'm afraid for use it's connectios in my switch. You believe that 4507R with supervisor V-10GE and IOS in last release would have problems of high cpu utilization, when to create etherchannel connection using different modules?



leighharrison Mon, 04/23/2007 - 14:21
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Hello again,


Have you implemented this yet?


I think that the best method would be to spread the etherchannel over the different modules.


As for the 10GE and the high cpu, there will always be teething problems with newer technologies, but I think that any feedback you could provide TAC would greatly help with any sort of development.


Let me know how it goes!


LH

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