Per packet vs per flow routing

I have a question regarding OSPF and how it would handle routing between two T1's by default. Is it going to per packet load balance between the T1's OR per flow choose which T1 to utilize for a given flow?

How do I set this to per flow if no the default.

Tx

Reply to
R Siffredi
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But what will happen on per flow if one of the T1's fills up with traffic, is there a way it would know to switch to other T1?

Should I c onsider a ppp multilink?

Reply to
R Siffredi

No. No routing protocol exists that takes load into account. Yes, EIGRP *can* use it as a metric, but it's zeroed out by default. Why do you suppose that is? The ability to detect congested links and react to it intelligently is quite challenging from a routing perspective.

That's one way to solve it if you have CPU to spare.

Reply to
Hansang Bae

Is there another way to solve it?

Tx

Reply to
R Siffredi

Unless you have a single source/destination pair that needs more than a T1 of bandwidth than flow based load balancing will be fine. If this won't work, than you can turn on per packet load balancing but it will cost you CPU cycles. If you have a low end router be careful. The reason load balancing defaults to per flow is because it is less CPU intensive and it works just fine 99% of the time.

Scott

Reply to
thrill5

Unfortunately, it is a 3825 router and I have a voice and video requirement. This eliminates per packet load balance. The endpoints are vpn devices, so it is all single source/dest pair and I need at least 2Mbps of the bandwidth. The only option then is ppp multilink. Correct?

Thanks for your help

Reply to
R Siffredi

In article , thrill5 wrote: :Unless you have a single source/destination pair that needs more than a T1 :of bandwidth than flow based load balancing will be fine. If this won't :work, than you can turn on per packet load balancing but it will cost you :CPU cycles. If you have a low end router be careful. The reason load :balancing defaults to per flow is because it is less CPU intensive and it :works just fine 99% of the time.

Unless, that is, you are using CeF -- modern CeF has little to no extra overhead to go per-packet. But if you are using flow caching instead of CeF, then per-packet balancing requires dropping down to process switching.

Reply to
Walter Roberson

CEF is a smarter switching method common on all new gear. It uses source/destination IP among other things to create the flow.

Reply to
Hansang Bae

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