[c-nsp] ASR 9000 as border router

[Mark Tinka]

On Thursday, December 30, 2010 04:11:16 am cisco-pe wrote:

> We have a core network based on CRS-1. The idea is to add
> an additional layer formed by the ASR-9K basically as
> concentrator/aggregator layer working as P.
> All the PE will be connected to the ASR-9K. We don´t want
> to connect the PE directly to the original core (CRS-1).
> What is your experience working with the ASR-9K in P/PE
> mode? What is your oppinion about our design,
> advantages/disadvantages? Thank you for your support.

We do exactly what you're doing, except with Cisco 6506 and 
6509-E switches. Let me explain:

What is not clear is whether your PE routers are in the same 
location or not. If they are, what you're actually looking 
to do is Layer 2 Ethernet aggregation within the same PoP, 
where you PE routers all aggregate into a Layer 2 core, 
which also interconnects the core routers (CRS in your 
case).

We do this with the Cisco 6500 switches as mentioned above. 
They allows us to reduce port count/cost on the core 
routers, as well as aggregate capacity into/out of the core 
with a few, high-bandwidth ports, e.g., N x 1Gbps or 10Gbps.

In such a case, the ASR9000 would be an expensive option 
since all you really need is pure Layer 2 Ethernet 
switching. However, I think one might be able to buy an 
ASR9000 cheaper than a Cisco 6509-E with a SUP720-3BXL, if 
you "spoke right", even if you just want the Layer 2 
Ethernet switching capability :-).

On the other hand, if your PE routers are scattered around 
the city/country, then yes, having an Aggregation layer is 
always useful to limit port count/cost in the core and 
introduce hierarchy. Ring topologies tend to be cheaper than 
point-to-point ones, but more so if your network is large 
than small.

Hope this helps.

Cheers,

Mark.
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