Configuring Load Sharing

Load sharing is the process of sharing the load between multiple destinations. It is possible to configure a router so that if a packet comes in destined for a particular address, the NAT process assigns it a new destination from its configured pool, in a round-robin fashion. If there are four addresses in the pool, the first four separate packet streams are assigned to a different IP address. Of course, each IP address must have the ability to process the requests, or else you have additional issues to deal with.

The following commands deal with implementing load sharing. Applying the NAT statements to the interfaces operates just as it did in the previous examples, so those lines have been omitted.

The first thing you need to do is identify the IP addresses that will be used for load sharing. In this case, four devices will be receiving packets:

 Router(config)#ip nat pool load-share 10.1.2.11 10.1.2.14 netmask 255.255.255.0 

The following command links the pool name to the access list that will be used to identify the IP address being matched:

 Router(config)#ip nat outside destination list 1 pool load-share rotary 

There are two important changes here, compared to the way this command was used with regular NAT. The first is that instead of the option source, we use the option destination. It tells the router which field in the IP header it needs to manipulate, the destination IP address. The second important component is the addition of the command rotary at the end. This command tells the router to do load sharing. Without this command, four packet streams would be translated and no other conversations could get through.

The access-list statement tells the router what destination IP address it's looking for:

 Router(config)#access-list 1 permit 10.1.2.10 0.0.0.0 

All the packet streams that want to be serviced use 10.1.2.10 as their destination. The router examines the IP header, replaces the destination address with one of the four from the pool, and forwards the packet to the appropriate device. No caching occurs.



CCNP BCRAN Remote Access Exam Cram 2 (Exam Cram 640 - XXX)
CCNP BCRAN Remote Access Exam Cram 2 (Exam Cram 640 - XXX)
ISBN: N/A
EAN: N/A
Year: 2003
Pages: 183

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