This is a general question. Does anyone know what are the latest/hottest LAN designs trends being used for large scale campus and data center networks these days? Are you using L3 designs such as OSPF with ECMP or L2 designs in these large scale networks? I am trying to figure out if using L3 design with OSPF and ECMP is becoming passé. Thanks for the input in advance.
I agree with Edison jrtuckiii. By limiting your L2 domain, you prevent spanning-tree loops. Here are the top two campus designs I have seen, granted like Edison said, depending on your requirement you could have completley different setups.
1) Having your Access Layer switches to your Distribution Layer switches run L2. Have your Distribution Layer switches to your Core Layer switches running L3, and obviously you'll want your core layer running L3. This allows your distribution to core layer to be L2 loop free. Plus you can also do load balancing as well with routing protocols (You can do the same as well, when con configure the load-balancing algorithm with etherchannels, but it's limiting).
2) A lot of people are buying Cisco Catalyst 6500 Series Switches and running VSS. This allows two physical switches to act logically like One physical switch. You can also have your access switches using Etherchannel to each switch in the VSS, which basically elements spanning-tree loops. You will still be running spanning-tree but you basically elminate the distribution layer.
You could write a whole volume of books on this subject, but those are a few popular and common ones.
Thanks. We have heard from some other network vendors that distributing L3 everywhere is an old model. Using newer protocols that other vendors have in their network equipment can aggregate the core using a L2 design and will eliminate the need for OSPF/ECMP distribution, which wil help with virtualization. What worries us is what you stated, "the core is now susceptible to loops and is no longer protected." We just want to make sure our network standards are not out-of-date and that we are not missing a new trend out in the industry.
Again, I said 'depending on customer requirements'. Virtualization will definitely push for L2 but in general you try to use L3 whenever is possible.
Not every company is doing virtualization and not every segment in your network needs a virtualization network scheme.
As a Network Engineer, if you know the pros and cons of each network design approach, you can make it work and sell it to your customers based on 'their' needs. That's something that 'us' as network engineers tend to overlook and try to impose 'our' preconceived ideas.
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Perhaps the "new" Data Center L2 fabric stuff, or Data Centers LANs that use enhanced Ethernet with Fibre Channel like properties.
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