Cisco 7200 PCI Limitations

david peahi davidpeahi at gmail.com
Mon Aug 6 11:47:30 CDT 2012


The 7200 architecture dates from the late 1990s, and is basically modeled
on a PCI-bus UNIX workstation from that era. The 7200 is usable today as a
WAN aggregation router for T1 access, and nothing else. Using it as a GiGE
transit router will place a non-deterministic node in the network, unable
to scale to the 4 GiGE full-duplex throughput. Even worse is creating a
portchannel out of the 7200 GiGE interfaces and using dot1q sub-interfaces
to emulate an Ethernet switch in 7200 software, then connecting the 7200
dot1q trunk to a modern Ethernet switch with a wire speed backplane (for
example a Cisco 3560X Ethernet switch).
Long since considered an unacceptable best practice (due to the 7200
backplane limitation vs adjacent, directly connected modern Ethernet
switches), Cisco is still teaching portchannel in its router configuration
classes, so relatively new network engineers have actually been known to
use this ill-considered configuration.
If a 4 port GiGE Cisco router is needed, then the ASR1001 is the modern
version of the 7206, with wire speed throughput.

On Fri, Aug 3, 2012 at 12:36 AM, shthead <lists at shthead.com> wrote:

> Hi all,
>
> I have a 7200 series router (7204) here and I am trying to figure out
> something with it. Currently the router has a NPE-G1 card in it, giving it
> 3 gig interfaces but I need an extra gig interface on it to make 4.
>
> Having a look around the available options are either get a PA-GE card
> that fits into one of the slots on the router or to get a C7200-I/O-GE+E
> (I/O controller with a gbit port on it).
>
> The PA-GE wouldn't be suitable as looking at the Cisco site the PCI bus
> will limit it to 300mbit full duplex (and it goes on further to say it will
> be limited to approx 200mbit in best case scenario due to the design of the
> card) [1].
>
> The other option left is the I/O controller. I found that you can get a
> port adaptor jacket card [2] for the 7200's that let you stick a normal
> interface card into the I/O controller slot (instead of the I/O controller
> itself).
>
> My main concern is if the jacket card uses its own PCI bus I am assuming
> the C7200-I/O-GE+E also connects via PCI which means it would be subject to
> the same limitations as the PA-GE.
>
> Does anyone have any idea if that would be correct and the only option for
> another gbit port would be to get another device?
>
> Thanks for the help
>
> [1] http://www.cisco.com/en/US/**products/hw/routers/ps341/**
> products_tech_**note09186a00800c814a.shtml#**backinfo<http://www.cisco.com/en/US/products/hw/routers/ps341/products_tech_note09186a00800c814a.shtml#backinfo>
> [2] http://www.cisco.com/en/US/**prod/collateral/routers/ps341/**
> prod_qas0900aecd8045055e.html<http://www.cisco.com/en/US/prod/collateral/routers/ps341/prod_qas0900aecd8045055e.html>
>
>


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