LAG with switch redundancy.

[Christof Schoeman]

Hi

I have a system that needs more than one Gigabit interface to cope with the transfers. At the moment I'm using LAG to bundle two interfaces, but this leaves me with no switch redundancy, as both interfaces need to connect to the same switch (see: http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=913233 )

We use Cisco switches and I've asked our network guys if I can use more than one switch - no go.

NetRAIN will give me switch redundancy, but I will only be able to use one gigabit link at a time - also no go.

Do you have any suggestions on how I can overcome this problem?

Regards

[Ivan Ferreira]

What if you install another network adapter with a separate IP address for the same network and use some kind of load balancing like a simple DNS round robin?

[Ivan Ferreira]

Sorry, I think that I did not understand well the question. You need redundancy for the adapter and the switch right? DNS round robind won't give you that because it won't detect if one of the connections failed, but a Linux Virtual Server could do that or another load balancer. But then, you will need a redundant Linux Virtual Server or load balancer.

[Christof Schoeman]

Ivan

Your suggestion about DNS round robin definitely got me thinking.

If I use four gigabit interfaces and create two NetRAIN sets, I can still use DNS round robin to alternate between the two.

Except, I don't think the other servers in the communication chain do DNS lookups often enough. Also, the majority of the traffic is generated by the server in question.

[Al Licause]

This shortcoming of Link Aggregation is more of a restriction imposed by the switch vendors since they require that all members of a LAG group be on the same switch.

You may be better off trying to apply pressure to the switch vendors to see if they have anything in the works to allow either a LAG group to be spread over multiple switches or the link multiple LAG groups between switches.

Good luck.

[Michael Schulte zur Sur]

Hi,

I wonder if it is possible to create a netrain interface made up of two lag interfaces. In that case you would have at least two gigabit connects on one switch which would switch to the other switch in case of a switch failure. The network doc is not too specific about that.

greetings,

Michael

[Al Licause]

No....you cannot use nr devices in LAG sets, nor can you use LAG sets to make up nr sets.