[c-nsp] Sharing router uplinks?

[Mark Tinka]

On Thursday, August 02, 2012 05:23:51 PM Scott Granados 
wrote:

> I second this, I think that point to point links make for
> the best connection type in this use for all the reasons
> mentioned ands also for the simplicity.  There's
> something to be said for keeping the core (and network)
> as simple as possible as long as the functionality is
> there.  I don't see what the original posters customer
> gains with the design and I think in general it's all
> downside.

Agree that point-to-point links between your core and edge 
devices are simpler, but they add considerable cost to your 
core router, particularly if the individual links are not 
fully utilized.

It "may" also stem from the fact that between 100Mbps 
Ethernet switches and Gig-E Ethernet switches, ATM formed 
many a switched core backbone on the Internet back in the 
day, in order to leapfrog the 100Mbps barrier. Of course, 
those had to be point-to-point links, but I digress...

I've run core environments based on few 10Gbps ports between 
the core routers and switches, and multiple Gig-E or 10Gbps 
ports between the edge and core switches, on shared subnets. 
No issues to complain about, be they monitoring, be they 
convergence. Depending on PoP size, switches have ranged 
from big chassis-based units to 1U desktop-sized platforms. 
But I will concede that this type of topology is not 
immediately intuitive in core routing environments, and I 
have come across such situations also.

An academic argument would also be that you use up a lot 
more IP addresses than you might have in point-to-point 
topologies, depending on the scale. But like I said, 
"academic" :-).

Cheers,

Mark.
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