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Etherchannel Grouping on 3750

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Jun 24th, 2009
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I want to build a redundant connection to my servers.Two switch and two switch each connected to as cross connection ie redundant connection.I want to achieve Load balancing when both switch works ie Active-Active and when switch goes down other switch must continues its operation.

Can i achieve this with out using HSRP.

If required i am ready to use HSRP but first i want to achieve L2 based redundacny and failover.



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Giuseppe Larosa Wed, 06/24/2009 - 00:53
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Hello Hari,

etherchannel provides L2 redundancy and failover and it can be used both for inter switch interconnections or for servers in active/active teaming.

I recommend to use LACP when building bundles with server NICs.

However, because communication is layered you need HSRP or other first hop redundancy protocol like GLBP to provide redundancy at OSI Layer3.

Hope to help


Joseph W. Doherty Wed, 06/24/2009 - 03:28
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So, you plan to have 4 3750 switches, configured as two stacks of two? If correct, you can configure a minimum of two link Etherchannel between the two stacks insuring there's one link per stack memember. Then dual home your servers to each stack.

As an alternative, you could place all 4 3750 switches into a single stack, and assuming your servers can Etherchannel with the stack, have each sever have a minimum of dual links to the stack, again links to different stack members.

For both of the above, HSRP would not be necessary nor direct benefit to your servers.

harisivaji Wed, 06/24/2009 - 07:37
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Sorry Jos,

I mis typed it is Two switch and Two Servers all are interconnected ie Meshed connection.

Its like:

Server1----Switch1 and Switch2

Server2----Switch2 and Switch1

Switch is 3750

My doubt can i use Etherchannel grouping for Load Balancing and Redundancy in Layer2 level

and HSRP for layer 3 level redundancy.




Joseph W. Doherty Wed, 06/24/2009 - 08:28
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Generally, to Etherchannel to a Cisco device, it needs to be the same logical device. Two independent 3750s wouldn't be.

For HSRP to be effective, the servers would need to bridge the same VLAN across their ports.

If you stack the two 3750s, then there's a good chance you can Etherchannel between the stack and your servers and you wouldn't need to use HSRP.

harisivaji Wed, 06/24/2009 - 10:58
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Consider HSRP,

for server1 sw1 will be active with SW2 in standby and server2 sw2 will be ative with sw1 as standby mode.ie both in active/active in load sharing mode normaly and in failover another one switch should take full burdern

How can i achieve this ...


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