Switch Interface Configuration – CompTIA Network+ N10-006 – 2.6

A switch can be configured with many different settings. In this video, you’ll learn about interface configurations, VLANs, trunked interfaces, link aggregation, and port mirroring.
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When you’re setting up a switch, there are a number of settings that you need to configure for the interfaces themselves. One is the speed of the interface. You generally would set it to something like 10 megabits, or 100 megabits, or 1,000 megabits per second. You could also configure the duplex on each individual interface to be running at either half duplex or full duplex.

This process can be configured manually for every single interface on the switch, or you can tell the switch, set the configuration automatically whenever a device connects to that interface. That way, you don’t have to set up anything manually inside the switch. This is something, though, that needs to match on both sides. The automated process is generally one that works well, but occasionally there will be incompatibilities and you might have one side set itself to full duplex, and the other side said itself to half duplex. And you’ll find that the performance is not really what it should be, because of the mismatch in the configurations.

You’re probably also going to need to configure an IP address inside of the switch. This IP address is generally used for management. It is a Layer 3 interface. You might also occasionally have these IP addresses configured on a per VLAN interface as well– especially if the switch supports a Layer 3 functionality inside of the switch, and can perform that routing inside the switch at the same time.

These IP addresses are generally used for management. We’re able to connect to that IP address from across the network. So you can sit at your desk, but be able to manage the device from elsewhere. To configure this address, we of course need the IP address. We also need the subnet mask associated with that IP address. You may be required to put it in dotted decimal notation, or you may be using it as a CIDR block notation inside of the configuration. You’ll probably want to define a default gateway for that IP address. And optionally, you may want to add DNS information, so that switch can access external devices by name, instead of IP address.

For VLAN configuration, we’ll want to define what every interface VLAN should be. Some may be on the default VLAN for that particular switch, or we may need to configure specific VLANs, depending on where people are connecting to the switch. You may have trunk connections between these switches, so you may have to configure certain interfaces on the switch to work as a trunk and connect to multiple switches together.

The .1Q trunk configuration is where we define what information is going to be tagged and sent over that trunk. If there is a native VLAN on these switches, that information is able to traverse the trunk link, without having tags being added to any of those frames. If it’s VLAN traffic, we will add a tag to the VLAN on the way out, and when it’s received by the other switch, the tag is removed, and the frame is placed on the proper VLAN on that particular switch.

Occasionally, you’ll want more than one interface connecting multiple switches together– especially if there’s a lot of bandwidth requirements for information traversing those particular switches. We call this link aggregation. We’re able to take multiple switches, add multiple links between them, and tell those two switches to treat those multiple links as if they were one high bandwidth connection.

In this particular case, we’ve taken four individual links, which means that we can have four times the bandwidth than having a single connection between switches. This is called port bonding. You’ll see it referred to as link aggregation, or a LAG connection. This is also something where you might want to enable something called Link Aggregation Control Protocol, or LACP. This adds some additional configuration management functionality between the switches, so that it is able to handle the LAG connection much more effectively.

If you need to troubleshoot some traffic on your switch, you may want to take advantage of the capability on your switch called port mirroring. This is able to take any traffic that might be going in and out of an interface, and send a copy or a mirror of that information to a protocol analyzer. You’ll see this used for intrusion detection systems, protocol analysis, or anything else where you need to capture the raw data going over the network. You can mirror traffic on the same switch from one port to another. Some switches support the capability to mirror across multiple switches. So you could have a protocol analyzer on one switch, and be able to see what traffic is traversing the network on a switch located elsewhere.