On Wednesday, August 01, 2012 05:46:30 PM Saku Ytti wrote: > It is doable but not optimal. It is questionable if any > benefits can be extracted in well designed network this > way.
I've had discussions with other operators in the past, who have been used to have a direct interconnect between routers in the PoP, and optionally, links to an Ethernet switch to aggregate downstream devices. I've tended to re-use the switched capacity and ignore the point-to-point link between the routers, at all bandwidth levels. Been doing that for the last several years, and no major drama - especially if you're not fully utilizing the ports on a point-to-point link. Certain topologies will require traffic mapping between routers more consistently, but those would be few and far between at the scale points affecting this decision, depending on the operation, e.g., MPLS-TE, IGP-based load sharing from upstream/downstream of the core network, e.t.c. > - You can possibly save port counts,... Which is not an unreasonable goal, particularly if ports cost additional money, space or power that one might not have. > but you lose > hardware liveliness detection, as you have switch > between core devices. Which means high convergence time > (lower quality) and possibly increased complexity (BFD). I've been running such topologies for several years, and IS- IS + BFD have not inconvenienced me once, whether in drills or real failure scenarios. Cheers, Mark.
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