Load Balncing across two LES10

Answered Question
Mar 26th, 2007
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Hello,


I have the follwoing setup:


2 companies trying to connect via 2 LES10 circuits (diverse for redundancy) Bothe LES10 circuits go into a VLAN on a 3500xl at each end. These two LES10 circuits will be etherchanneled. Servers at either company talk to each other via a checkpoint firewall which has one interface going into the same vlan on their respective 3500 XL switches. The setup is as attachment.


My question is this: will all traffic always go across the same LES 10 as there is only one source and dst mac involved (checkpoints) for comms? Is there anyway to balance this traffic with the present setup?




Attachment: 
Correct Answer by Jon Marshall about 10 years 4 months ago

Hi


No problem.


In answer to your question no the etherchannel would not have to have an IP address. It can be layer 2.

When you load balance on the source and IP address you are talking about the client ip address and the server ip address not any IP addresses on the switch. So a layer 2 etherchannel can quite happily load balance on src/dst IP address.

When you load balance on src/dst IP address this is not a layer 3 decision, the traffic is still switched at layer 2, the IP information is only used to decide which link within the etherchannel to send it on.


HTH


Jon

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Jon Marshall Mon, 03/26/2007 - 12:55
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Hi


Yes as the 3500XL uses only source and destination mac addresses to load balance.

In the situation you describe you would need to balance on src / dst IP address or src / dst port numbers.


Attached is a link to a doc on etherchannel load balancing and which switches support which type of load balancing


http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094714.shtml


You could upgrade your switches if that is possible.


HTH


Jon

rosco1976 Tue, 03/27/2007 - 01:15
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Jon thanks for this.


I presume to balance on ip/port number the port channel would have to have an IP address i.e. it couldn't be layer 2 like my present setup?


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Jon Marshall Tue, 03/27/2007 - 01:52
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Hi


No problem.


In answer to your question no the etherchannel would not have to have an IP address. It can be layer 2.

When you load balance on the source and IP address you are talking about the client ip address and the server ip address not any IP addresses on the switch. So a layer 2 etherchannel can quite happily load balance on src/dst IP address.

When you load balance on src/dst IP address this is not a layer 3 decision, the traffic is still switched at layer 2, the IP information is only used to decide which link within the etherchannel to send it on.


HTH


Jon

rosco1976 Tue, 03/27/2007 - 02:31
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Interseting.


Jon thats great that's really cleared things up was unsure if IP information could be used when switched at layer 2. Thanks again!



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