Multi-layer Switching at the Core?

From Diane Teare book:

Because core devices are responsible for accommodating failures by rerouting traffic and
responding quickly to network topology changes, and because performance for routing in the
core with a multilayer switch incurs no cost, most implementations have multilayer switching
in the core layer. The core layer can therefore more readily implement scalable protocols and
technologies, alternate paths, and load balancing.

Do people really use multi-layer switches at the core?

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Comments

darkerosxx

Well in thinking about it, I guess multi-layer switches at the core are fine for enterprises. I was thinking about ISPs, since that's where I work. We don't use switches in the core anywhere.

malcybood

darkerosxx wrote:

From Diane Teare book:

Because core devices are responsible for accommodating failures by rerouting traffic and
responding quickly to network topology changes, and because performance for routing in the
core with a multilayer switch incurs no cost, most implementations have multilayer switching
in the core layer. The core layer can therefore more readily implement scalable protocols and
technologies, alternate paths, and load balancing.

Do people really use multi-layer switches at the core?

Simple answer is yes.

We use layer 2 VLAN separation for server access ports and OSPF to route traffic from the core switch to i.e. the WAN core router / WAN sites. Nortel Passport core switches talking to Cisco routers hence the OSPF protocol selection and not EIGRP.

Paul Boz

I used to work for a fiber to the home ISP and we used C10k's as our aggregation and atm-to-IP conversion routers with c7613 multilayer switches in the core. The high-end cisco switches are capable of incredible backplane bandwidth and route packets at wire speed. We had the network segmented with vlans and the core switches routed traffic between them.

networker050184

I see a lot of Juniper routers in the core of service providers I have seen, but at the enterprise level 6500's doing the routing is the norm.

darkerosxx

yea we're using junipers at all of our cores nation-wide

Paul Boz

networker050184 wrote:

I see a lot of Juniper routers in the core of service providers I have seen, but at the enterprise level 6500's doing the routing is the norm.

Junipers are great BGP routers. Generally they're used in the core when BGP is. At my last job we used Juniper M10's at the edge for BGP then interfaced them with our core as a peering module. We had the Junipers configured as a route reflector with two clients (each client was an OC12 to a different upstream peer). All IP traffic would be on one vlan with a default route pointing at the Juniper BGP route reflector. From there best-route decisions would happen. This is a pretty standard multi-homing scenario and solution when the ISP/network in question isn't a carrier.