Maximum Throughput for Cisco ISR 2911

[Enrique Gonzalez Corral]

Our client currently has a ISR 2911 connected to their ISP. They are increasing the bandwidth offered to them, so they now have a 2Gbps connection. What is the parameter relevant for this configuration? Throughput? what is the maximum throughput available in a ISR 2911? How could we get the 2 Gbps that our client needs?

[Mark Malone]

Hi a 2gb wan connection on a 2900 series is that what your talking about ?  that's not going to happen , you would need an ASR or a high end 4000 series ISR to get near that , its capped in the docs at 180mb and that's without using any services all which will effect throughput when turned on

were using ASR 1001x just for 150mb wan links

http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf

ISR G2 2911 180.73 MBps or 353,000pps

[Enrique Gonzalez Corral]

Thank you all, very useful information on each one of your answers!!!!!

[hussain85]

hi, kindly advise, what max speed cisco router model CISCO2911/K9 can support?

[Joseph W. Doherty]

That was already specifically answered in my earlier post.

[hussain85]

but you answer for ISR G2 2911?

[Joseph W. Doherty]

Right, as far as I recall, there's only one performance level for the 2911. Your K9 suffix should be an IOS with crypto feature set.

[Reza Sharifi]

Couple of issues with using 2900 for 2 Gig Internet.

The 2911 comes with 3 10/100/1000 copper ports.  Of course, this does not mean you can push a Gig of bandwidth using these interfaces as there is limitations on throughput and switching (see Mark's link).

The other issue is if you use the 2900 to go from one gig to 2, you now have to use 2 1Gig interfaces. So, you need to aggregate the interfaces with Etherchannel or some other way and not even sure of the providers will do that.

So, you need a device (ASR series) that can handle a 10gig interface with a 2 Gig commit from the provider.

Most providers offer 2Gig commit, 5Gig commit or 10Gig which is the whole interface. Obviously the higher the commit the more $$ you have to pay. The good news is that the price for 10Gig is dropping fast, as more and more providers are offering them.

HTH

[Palani Mohan]

Enrique

Throughput is a function of two factors:

• pktSize
• Features configured

At a very high level, the router/CPU spends its resources to move pkts from the interface where it was received to the interface through which the pkt is destined to go out. The core functions associated with this include:

• inspect the ipHeader
• decrement TTL count by 1
• do a lookup, to identify the outgoing interface

Let's say the CPU spends 1 unit. Now, if you send 10 pkts to this router, the CPU will spend 10 units. If these 10 pkts are 1500 bytes long, then the throughput handled would 10 times 1500 which is 15000bytes. On the other hand, if the pkts are 100 bytes long, then the throughput handled will 1000bytes. Notice how the throughput varies based on pktSize?

With no features configured, with average pktSize of 400bytes, 2911 can handle 800Mbps of throughput. Needless to say, that if your customer traffic is made of larger pkts, you will get higher throughput. Similarly, if the customer traffic is made of smaller pkts, then the throughput will be less.

Extra features (ACL, NAT, QoS, NBAR, VPN and such) means the CPU has to spend extra CPU units. In other words, when features are configured, you can expect lower throughput than the 800Mbps stated earlier.

If you are not registered at http://www.ciscolive.com/global/, go ahead and register. You will have access to past presentations. One of them from (almost) four years ago is BRKARC-3001. Its title is Cisco Integrated Services Router G2  Architectural Overview and Use Cases. Per this, the router that can handle 2Gbps throughput would be either 4451-X or the ASR 1000/1000-X series.

I hope this helps .... Palani

[Joseph W. Doherty]

what is the maximum throughput available in a ISR 2911?

Cisco documents the best RFC 2544 throughput of an ISR 2911 at 3.371 Gbps!  But, you're unlikely to come near that in the "real world".

Cisco recommends the 2911 for up to 35 Mbps of WAN bandwidth.  Cisco's recommendations tend to be very conservative, so that you don't exceed the capacity of the device.  You might be okay supporting up to about 50 Mbps.  What you need depends much on your configuration and what your traffic is like.

If you want to guarantee 2 Gbps of performance, as already noted by the other posters, you'll need a high end ISR 4K or a low-end ASR 1K.

PS:

Depending on your feature needs, a L3 switch might also be a possible candidate.

[h-ramadan]

Hi Joseph

Kindly dows this WAN recomendations applyied on the Switch Gigaport of this Router 2911 or this is on the Modem WIC only

Many thanks

[h-ramadan]

I mean what do we mean by WAN here is it the Giga interface of this Router as well ?

[Joseph W. Doherty]

Although Cisco, in their documentation (see attachment's page 7), has "WAN circuit speed", the recommendation is really about the overall capacity of the router.

Concerning WIC modules, those often have their own bandwidth limitations, both for the particular WIC variant, i.e. WIC(8Mbps??[WIC-1SHDSL-V2/3 supported 4.6 Mbps])/EWIC(400Mbps)/HEWIC(800Mbps), slot and sometimes the module, itself, and/or router's "bus" supporting the WIC slot.