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DIFFERENCE BETWEEN LOAD BALANCING ..........

giuliano
Level 1
Level 1

Hi.

Someone can tell me the difference between CEF load balancing and EIGRP load balancing?

Setting 2 static default route with two different interfaces enable the router to do load balancing (per packer or per destination)?

Thanks.

4 Replies 4

j-bliss
Level 1
Level 1

Gilles Dufour
Cisco Employee
Cisco Employee

CEF alone will not achieve loadbalancing.

Actually CEF uses the information in the routing table to create is

own CEF table.

If there is multiple routes for one destination, CEF will do the loadbalancing.

To populate the routing table with multiple entries, you can use Eigrp, but any other routing protocol or even static routes or a mix of both.

Once CEF knows it has to do loadbalancing, you can select how it will achieve it.

You can select per-packet or per-destination.

With per-packet, every packet will submited to loadbalancing.

With per-destination, all traffic going to host x.x.x.x1 will use link1 and every traffic to host x.x.x.x2 will use link2.

To select which type of loadbalancing, use the command 'ip load per-packet' or 'ip load per-destination'

If you are not using CEF, but still have multiple route for one destination in your routing table, the router will still do some loadbalancing.

If no fast switching is configured at all, the loadbalancing is per packet and you can not change it.

If you have setup fastswitching (but not CEF) the router will loadbalance per destination.

So, 2 static default routes will be enough to achieve loadbalancing.

Thanks fot the information, but i still have one more question if possible.

With fast switching or CEF doing load balance per destination, the load balancing is done by destination host.

But how? Using some sort of round robin?

If i ftp to an host and one of my friend ftp to the same host, i use link 1 and my friend use link2 or not?

If not the load balancing per destination is some sort of load sharing .....

Thanks.

Load balancing with fast switching is destination based--the first packet towards any given host is process switched, and the round robin counter in the routing table determines which route the fast cache entry will be built to. This is a simple round robin counter.

CEF builds out a series of tables, and runs a hash computation over the source and destination addresses to determine which path to use, so there is no round robin counter.

Russ

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