router throughput

[rickrude11]

I am struggling to find an answer to this.

I have a gigabit dark fiber wan and need a router at each end capable of routing at a potential of 1Gb/s.

I initially thought that seeing as the 2821 and 2851 routers come with 2x gigabit interfaces, then they must be able to handle at least near that, but apparently i am mistaken.

Will the 3825 do this? what sort of throughput do these max out at?

cheers!

 

[vipergg]

If you need that kind of thruput thru a wan then you might want to look at L3 switches with fiber links in them like a 3750 or 3560 .

 

[burtsbees]

I found out not too long ago (I believe from vipergg) that an interface will not have what is listed as its true throughput with the lower models, I.E. 100MBps on a 2620 will only put like 15MBps through, or something like that. Why this is is beyond me...

Burt

 

[BuckWeet]

There are pretty much no routers that Cisco makes that are software based can do line speeds on the interfaces they support.

As the previous poster said, you should look at a layer3 switch.

 

[jneiberger]

Yep, absolutely right. There is no low- to medium-size Cisco router that could handle those speeds. Almost no low- to mid-size router can forward data at the speed of its interfaces. For example, routers have had Fast Ethernet interfaces for years, but very few routers could even come close to being able to forward traffic at 100 Mbps.

 

[rickrude11]

Thanks for your recommendations!

So even with CEF technology, a 3825 router wouldn't handle 1Gb/s thoughput? Why can a switch switch layer3 faster than a router?

 

[BuckWeet]

The switch can do it because it uses ASICs to do the forwarding, but it is limited when it comes to advanced features. ASICs are basically semiconductors built for a specific task, in this case forwarding traffic. The 3825 like other routers are software based and use a central processor like a computer. It can offload some forwarding using CEF though..


BuckWeet

 

[dearingkr]

The distinction between a router and a switch has become somewhat blurred in the last few years.

You have layer 3 switches that have some of the basic capabilities of routers.

And you have routers with built-in switch modules.

In your case, you need high bandwidth.
As vipergg said, look for a layer 3 switch that has the basic routing capabilies you need.

MCSE CCNA CCDA

 

[rickrude11]

So cef caches lookups but it is still software based so it's slower?
Does anyone know if there has been any benchmarks done?

 

[BuckWeet]

rickrude11... exactly

 

[Belushi]

My best advice for alower cost router that can handle this is the ASR series router platform. You can get an ASR for a relatively cheap price (key word here is relative) that can easily handle layer 3 forwarding of those types of speeds.

Problem with a layer 3 switch 3560/3750/4500/6500 is that they aren't trully routers regardless of what anyone here says. Yes they have routing functionality and router interfaces, especially when you get into some of the modules that 6500 can support. However, there is a movement within Cisco to remove most routing functionality from the 6500 line and put it into the 7600 line.

Anyway, routing at gigabit speeds is no small task. As youi already noticed just because you have a gigabit interface doesn't mean you have a routed gigabit interface. Yes, you can connect your layer 2/3 switches together over them but I assure you that the same funcionality will not exist that you can get with a rotuer like Egress queueing for QoS, advanced routing, firewalling, etc.

ASR is the cheapest and best way to go as of now. With the 3800 series line you are basically capped at roughly DS3 speeds. Yes, you can support faster modules like an OC3 but that doesn't mean you can route at it!

 

[rickrude11]

I appreciate all the feedback!

I think I will go for the L3 switches. Belushi, I see where you are coming from but I have no need for anything but but basic ACLs. These are just for internal traffic between 3 offices.

Still think it's stupid having gigabit interfaces on these routers that can't even route at 100mbit.

rick

 

[jneiberger]

It's not stupid, rick, it's the way it's always been. There is no low- to mid-level router from any manufacturer capable of moving traffic at constant line speeds. It just doesn't happen.

 

[burtsbees]

I think his point is why call them GB interfaces? Why not 10/100?

Burt

 

[jneiberger]

If it connects using 1000BaseSX technology, it is a gigabit interface regardless of the actual throughput on the device. If it connects using 100BaseTX, it's a Fast Ethernet interface over copper.

There is a difference between interface type and throughput. No router on the planet has claimed to be able to deliver line rate on all of its interfaces. The variety of interface types increases your connectivity options, but it doesn't in any way mean that you can actually move data at line speeds.

 

[BuckWeet]

Good way to think of it is if i have a core switch that only has gige interfaces. I need a WAN router to connect at gige speeds. What if you have a WAN interface that is OC3 or OC12 speeds. You definately need just enough box for those interfaces..

It is deceiving though..

BuckWeet

 

[ssiva1086]

I have no idea....