help me understand router performance

[Tod Larson]

Please see the report from Cisco.

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

This says an ISR G2 3945 can achieve 502.78 Mbits when CEF fast switching. Is this per port or total for the whole box? Since the router will hold dozens of switch ports and several gig routed ports I don't understand what this half gig switching speed means. Thank you.

[Leo Laohoo · Accepted solution]

Is this per port or total for the whole box?

This is the entire CHASSIS or "box" as you'd call it.

Another thing to consider, the value is expressed in HALF duplex and without any encryption.

If you want FULL duplex then halve the value.  If you want full duplex and with encryption then take the full value and divide it by a factor of four (4).

 I don't understand what this half gig switching speed means.    

If you take the value of 502.78 and divide it by four (4) this gives you 125.7 Mbps.  How do you expect 125.7 Mbps of traffic to pass through a 100 Mbps interface?  You need to have a 1000 Mbps (or 1 Gig) interface.

[nkarpysh]

Agree with Leo.

Adding to that please note that CEf switching here is not the regular L2 switching within same VLAN. This is basically routing  between different subnets which is done in HW. All routers are limited in routing performance that is why we see 0.5GB number here. Though considering that router is used to connect to WAN where speeds are still much smaller that is a good throughput.

Nik

[Joseph W. Doherty]

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Posting

"All routers are limited in routing performance . . . "

Doesn't Cisco sell the 7600 and CRS1/3 series as "routers" . . . their routing performance isn't too limited, maybe not all? 

[paolo bevilacqua]

But some routers are more routers than others.

[Leo Laohoo]

Thanks Tod.