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Joe Ripley

Cisco ISR 4331 Router Capacity

I've always been confused with capacity on Cisco routers... especially now with these 'license based' systems.

Anyway, venting aside, my question is about the speed/data rate on the ISR 4331.  The data sheet says that it can packet switch at up to 100 mbps.  It also says that with a 'performance license upgrade' it can packet switch at 300 mbps.  This license upgrade is strictly software based, no additional hardware is necessary.

So, does that mean that the system is choked to 100 mbps out of the box?  Even with the GigabitEthernet interfaces, it will only route data at 100 mbps?

Or, are these speed limits more like the older ISR routers (like the 2801)?  Those systems had FastEthernet interfaces and could route at nearly the wire speed.  The router would be throttled back when you started doing extra stuff like NAT, VPNs, etc.  This was a CPU/memory limitation though.  The new ISR 4331 has tons of DRAM and CPU power to spare...

My client currently has 100 mbps fiber service and is looking to upgrade to 1000 mbps service.  Is the 4331 up to the challenge?  Or is 300 mbps (after a $1000+ license installation) the best it can do?

Thanks again for any info you guys might have!


Joe Ripley


No it can probably do more than 300Mbps.  What Cisco has done is try to end the confusion and disparity between what they say they can do and what is truly practically applicable.  First thing to remember is that gotcha that we all forget when looking at that number form every vendor, that is aggregate bandwidth.  That means that if you purchased a 50Mbps download x 50 Mbps upload circuit, you would have hit full capacity of you router.  But for once, this is they real number.  That is what it can do with all the major features enabled, but nothing more since it has be rate limited to ensure the stability of the system.  The feature license unlock cores on the multicore CPU, thus enabling double the processing and functional capacity of the platform. I have several of these in use doing multi-VRF routing leaking, local NAT, Zone Based stateful firewall, and DMVPN with highest VPN security suite settings.  They hold up to the advertised throughput without breaking a sweat.  The IOS-XE's Linux based shell with IOS features boxed within their own resource pools or containers has allowed Cisco to actually fence off resources accurately.  I must say I have been very very happy with these systems. 

Again, don't forget bandwidth is aggregate.  Doing things such as router-on-a-stick intra-VLAN routing at the router backplane via sub-interfaces can quickly eat up those resources, as they did on previous families.  You will want to do VLAN termination on the switch below the router to ensure that doesn't happen. Good luck!



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