What Is Distribution Switch and Why Do We Need It?

We know that in data centers a three-layer hierarchical model contains core layer, aggregation/distribution layer and access layer. In this network topology, corresponding network switch is implemented in different network layer. A core switch is a high-capacity backbone switch, which locates in the topside for WAN access and centralizing multiple aggregations in the core. Thus backbone core layer switch is often a fiber switch for advanced optical link. An access switch or an edge switch is for direct end devices and hierarchy connection. But what is distribution switch? What are the functions of distribution layer switch? And what’s the difference between aggregation switch vs core switch and distribution switch vs router? This article may help.

what is distribution switch and aggregation switch function

What Is Distribution Switch?

A distribution switch is a distribution layer switch, which uplinks to upper layer core switch and links down to the access/edge switch. Simply put, an aggregation switch in between functions a bridge between core layer switch and access layer switch. This is also the reason why we call distribution switch as aggregation switch.

Distribution Switch Functions

Why distribution layer switch is needed in network layers? In general, aggregation switch reacts on multiple switch aggregation and layer 3 routing functionality. It also supports complex policy implementation such as QoS and packet filtering. Highlights, distribution switch employs Access Control Lists (ACL) to offer optimized security policies. This security capability enables aggregation switch to decide which traffic can be permitted for communication. Here we illustrate the necessities of distribution layer switch into details by comparing it to other switches and routers.

  • Distribution Switch vs Access Switch

Usually we employ gigabit Ethernet switch in access layer 2 to run at 1Gb. When traffic driving from a layer 2 switch, the network topology requires a device with layer 3 features to process it to VLANs. Aggregation switch is often a layer 3 switch, so it supports inter-VLAN routing over a layer 2 switch. When multiple access switches among different VLANs are required to be aggregated, a distribution switch can achieve inter-VLAN communication.

  • Core Switch vs Distribution Switch

For core switch vs aggregation switch, one question may come in mind: why not directly connecting access switch to the core switch? An important reason is for convenient network access. When there are dozens of clients spreading over different offices in 5 buildings, we can deploy a distribution layer 10GbE switch in the center of each building to connect multiple access layer gigabit Ethernet switches in different offices. Then the 5 distribution switches can easily link to a 40GbE core switch in data centers. There are cases of combining collapsed distribution and core into one when there are only several severs and end users. We also call such switch as collapsed core or collapsed backbone since distribution layer switch is combined.

using fs 10GbE switch as distribution switch

Figure 1: Deploying FS S5800-48S6Q 10GbE switch with 6 40G QSFP+ uplinks as distribution switch in three-layer hierarchical model.

  • Distribution Switch vs Router

Generally, both a router and distribution layer switch has layer 3 routing functionality. But there is some distinctions. Compared to layer 3 switch/multilayer switch, a router has full layer 3 features and intact routing functionality like Internet Service Provider (ISP) and WAN. A aggregation switch combines layer 2 switching technology with layer 3 routing technology in one hardware. So a layer 3 distribution switch owns edges over router as switch while possessing inter-VLAN routing functionality. Besides, as a router a layer 3 distribution switch can route packets more quickly than a router due to functionality to make cache entry in its fast memory.

deploy layer 3 switch distribution switch over layer 2 switch and routers

Figure 2: Scenarios to deploy layer 3 switch – distribution switch over layer 2 switch and routers.

Conclusion

Despite advanced features of policy-based network connection, distribution layer switch functions aggregation and routing. As an aggregation switch, distribution switch connects multiple access switches and centralizes them to core switch. As a layer 3 switch, distribution switch adds routing functionality to achieve fast and easy inter-VLAN routing communication. As thus distribution switch deployment changes the situation that subnet must relay on router to manage network. And solves the issue of low speed and complexity caused by traditional routers.

Cloud Core Switch—An Economic Choice for L3 Switch

MikroTik Switches have been popularly received favorable reviews, and this is inseparable with their keeping on the bleeding edge of switching technology. As a new member of MikroTik Smart Switch series, cloud core switch, also called cloud router switch, combing the best features of a fully functional router and a Layer 3 switch. That is to say, this cloud router switch works as both switch and router to connect the VLAN. This article would mainly discuss about cloud core switch, CRS226-24G-2S+RM switch and its connectivity solutions, as well as the reasons why they are economic choice for L3 switch.

About Cloud Core Switch

The cloud core switch, or cloud router switch, abbreviated as CRS, is a highly configurable switch, powered by RouterOS. It has 24 Gigabit Ethernet port. The Ethernet port 2-24 are switched, and the device can be accessed via these ports through the IP 192.168.88.1. Ethernet port 1 is configured as a DHCP client and has firewall on it. The SFP port is configured the same way as Ethernet 1, with a firewall and DHCP client on it. For the cloud router switch, there are nine models currently available. Here lists three different cases of the cloud core switch:

  • CRS125-24G-1S-2HnD-IN (integrated wireless, indoor case)
  • CRS125-24G-1S-IN (indoor case)
  • CRS125-24G-1S-RM (rackmount case)

MikroTik cloud router switch

Figure1: MikroTik cloud router switches(Resource: www.MikroTik.com)

Cloud Core Switch CRS226-24G-2S+RM

As one of the cloud core switches, CRS226-24G-2S+RM have been highly favored by most people. CRS226-24G-2S+RM is a fully functional layer 3 cloud router switch powered by Router OS, which is also available in 1U rackmount case. It comes with a special switch menu which includes all the specific configuration options for switches. It has 24 Gigabit ports and two SFP+ cages for 10G connectivity in which first SFP port supports 1.25G/10G modules and second port only 10G modules. Ports can be removed from the switch configuration and used for routing purposes if needed. The most distinctive feature of CRS226-24G-2S+RM is that uses a new class of switch chips, which allows us to have two SFP+ ports for 10G connectivity. The main features of this cloud core switch are listed in the following:

  • Fully manageable L3 switch, full wire speed switching
  • Configure ports as switch, or for routing
  • If required, full RouterOS power right there
  • SFP+ ports for 10G connectivity

CRS226-24G-2S+RM_big

Figure2: cloud core switch CRS226-24G-2S+RM(Resource: www.MikroTik.com)

Connectivity Solutions for CRS226-24G-2S+RM

As being mentioned, the cloud core switch CRS226-24G-2S+RM has 24 Gigabit ports and 2 SFP+ ports. For the twenty-four 10/100/1000 Ethernet ports, you could use both network cables and optical transceivers to connect. The transmission speed of Cat5 and Cat5e cables can be up to 100 Mb/s and 1G respectively. Besides, you can also use 10/100/1000BASE-T copper transceiver to make network connectivity. But it costs more than the network cables. In terms of 10G SFP+ ports, there are also two connectivity approaches. You can use both 10G SFP+ modules and 10G SFP+ DAC copper cable to connect. Relatively speaking, the 10G DAC cable is cheaper a lot than the 10G transceiver. But if transmission quality is your pursuit, and then 10GBASE SFP+ transceivers would be a good choice.

Why Are Cloud Core Switches Economic Choice for L3 Switch?

According to the above description, cloud core switches are powered by Router OS. RouterOS lets you add upper layer functionality. The cloud core switch is very far below wire speed when doing layer 3 or above. In fact, the cloud core switch is more of a bare-bones layer 2 switch that has an embedded low-horsepower router. In short, the switch features are useful for making bridges that work at wire speed, but they’re limited to simple forwarding and vlan handling. The bridge feature lets you glue almost anything together, and gives lots of filtering/manipulation tools, but it cannot perform at wire speed because it uses the main CPU. Last but not least, the average prices of Mikro Tik cloud core switches are not more than $150, you can check them by this link.

Conclusion

Cloud core/router Switch is a managed switch that runs RouterOS and SwitchOS, which delivers a high performance as a Layer 3 switch. They allow to manage port-to-port forwarding, apply MAC filter, configure VLANs, mirror traffic, apply bandwidth limitation and even adjust some MAC and IP header fields. The economic L3 switch including several switch models covering wide range applications, like enterprise network and home network.