Etherchannel settings of 3750 switch for NICs team

Unanswered Question
Mar 30th, 2009

As the server side, we could setup NIC team as active/active(LB) or active/standby (HA).Is there any different settings on 3750 switch? Although I just searched the topics on Cisco forum, I am not sure if I am correct, please advice!

If we use HA mode on server side, I need configure etherchannel as LACP mode.

If we use LB mode on server side, i do not need setup any etherchannel for it.

Thanks for your help!

I have this problem too.
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Edison Ortiz Mon, 03/30/2009 - 12:28

Actually, the other way around.

Active|Active on the server side requires etherchanneling config at the switch since the server will be sending the same MAC address from both NICs.

Active|Standy requires no configuration at the switch since the server will have an unique MAC address per NIC.

HTH,

__

Edison.

HWangLoyalty_2 Mon, 03/30/2009 - 12:41

Thanks. It looks like I mess up :)

To A/A mode, both NISc share the same MAC address, how about the IP address? Share the same VIP address or use itself address? Why do we use etherchannel to fix the same MAC address issue?

To A/S mode, do both NICs share the same VIP address?

Thanks again!

Edison Ortiz Mon, 03/30/2009 - 13:04

To A/A mode, both NISc share the same MAC address, how about the IP address?

On the server side, an IP address must be assigned to the teaming - this address will be shared among members of that team.

Why do we use etherchannel to fix the same MAC address issue?

The switch forms a table where each device is represented by an unique MAC address. That's how the switch makes its Layer2 forwarding decision.

As packet exits from the switch or enters into the switch, they are destined to/from an unique MAC address. If you have a duplicate MAC address in the table, the switch won't know which MAC address to send the packet to.

Same behavior as having duplicate IP address in the network.

To A/S mode, do both NICs share the same VIP address?

Yes, but only one is active at the time.

__

Edison.

HWangLoyalty_2 Mon, 03/30/2009 - 13:30

That's great, but I need clarify some questions.

a.On the server side, an IP address must be assigned to the teaming - this address will be shared among members of that team. ----Is the VIP address instead of another IP address assigned to individual NIC? Is the shared MAC-address VIP as well?

---- Did i have to use LACP mode? how about PAGP or on mode?

b.To A/S mode, how about the MAC address shared? Is it VIP one? It is not, how to refresh arp table on switch side if the failover was happened?

thanks again!

Edison Ortiz Mon, 03/30/2009 - 14:31

Is the VIP address instead of another IP address assigned to individual NIC?

I'm not an expert on the server side of the configuration, you must check the manual from the OS or tool that you are using to create the NIC team in order to get that answer.

Did i have to use LACP mode? how about PAGP or on mode?

PAgP is Cisco proprietary, not supported on Server NICs.

You can use on mode but I wouldn't recommend it as it forms a channel unconditionally, in other words, it doesn't check if the server is ready for channeling..

To A/S mode, how about the MAC address shared?

Not sure if the MAC address is shared (again consult the documentation on your product) but the switch will see an unique MAC address from each NIC.

__

Edison.

HWangLoyalty_2 Wed, 04/01/2009 - 13:29

Hi Edison:

As we know, we could use the etherchannel technology on both server and siwth side if two NICs are connected the same switch or cross-stack switch (only support "on" and "LACP").But if when two NICs with A/A mode are connected to separate access switches, I think it would cause arp conflict issue on a core switch because there is the same IP address with the different MAC address. How to fix this issue on cisco device? Or we need fix it on the server side? Thx again!

Edison Ortiz Wed, 04/01/2009 - 13:33

I think it would cause arp conflict issue on a core switch because there is the same IP address with the different MAC address. How to fix this issue on cisco device?

Unsupported design.

You need to configure the server for Active Passive for this design to work.

___

Edison.

hobbe Thu, 04/02/2009 - 08:08

To have the A/A on to physically separate switches you could use fx 3750 and form them into a stack.

you would then have the benefits of different switches but at the same time the problems with having to shut them down to upgrade and so on.

Thats the only way I think you can use A/A with separate switches the way described above.

good luck

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