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Cisco Employee

Load Balancing Static Default Routes

Wondering if simple load balancing Outbound can be accomplished by defining static default routes with the same cost to say two different next hops. Does anything else need to be enabled (ecmp maybe ?).

Right now I'm connected to two different ISP's via two routers and running BGP to both, but only getting local ISP routes. Therefore there is a default route on both routers pointing to it's local ISP. Understand there are different ways to skin a cat but I don't want to make a lot of changes to the existing environment. Just looking for a quick fix to use the second ISP connection for outbound traffic.

Cisco Employee

Re: Load Balancing Static Default Routes

yes - 2 default static routes will get you to loadbalance the traffic between your 2 ISPs.

Depending on your switching method, you will get per-packet or per-destination load-balancing.

process switching = per packet

fast swtiching (not cef) = per destination

cef = configurable with the command 'ip load ...'

New Member

Re: Load Balancing Static Default Routes

Is there any documentation on advantages and disadvantages of configuring load balancing between process switching, fast switching, and other options like BGP.

Cisco Employee

Re: Load Balancing Static Default Routes

no document that I know off.

But I can try to explain briefly.

process-switching loadbalancing = per-packet.

You have true loadbalancing but process switching is also called the slow path. More CPU intensive so worst performance.

fastswitching loadbalancing = per-destination.

FastSwitching give you better performance in general but the loadbalancing is done per destination. So, if at a certain time you have only traffic from A to B, only 1 of your isp connection will be used.

CEF is the best solution since it is fastswitching and it let you chose the loadbalancing mode.

New Member

Re: Load Balancing Static Default Routes

One Idea would be is to get deafults from both ISP's via bgp ...

New Member

Re: Load Balancing Static Default Routes


Can you provide some further information. Are you using NAT or are your addresses Internet valid. If NAT, do you have pools for both ISP's? Can you provide more general information on your setup of addresses and your flow to the ISP's?


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