How to Configure DHCP for Multiple VLANs?

Almost every device connected to the Internet needs an IP address. Previously, the countless IP addresses are assigned manually, which costs a lot of time and energy. As DHCP emerges, IT specialists are not required any longer to spend countless hours providing IPs for every device connected to the network device. But what is DHCP? How does it work and how to configure DHCP for multiple VLANs?

What Is DHCP?

DHCP – Dynamic Host Configuration Protocol is a network management protocol used on TCP/IP network. There may be at least a DHCP server and many DHCP clients. The DHCP server allows the client to request the IP addresses and other network configurations from the Internet service provider. This process eliminates the need for administrators or users to assign IP address to network devices one by one. Using this protocol, the network administrators will just set up the DHCP server with all the additional network information, and it will do its work dynamically. Both network switch and router can be configured as a DHCP server.

How Does the DHCP Process Look Like?

For the DHCP client that hasn’t accessed the Internet before, it will undergo 4 phases to connect the DHCP server.

dhcp process

Fig 1. DHCP process

1.Discover

DHCP client after being activated will first send a broadcast message to try to look for DHCP servers. In this way, the client request IP address from the DHCP server.

2.Offer

When the DHCP server gets the message from the client, it looks in its pool to find an IP address it can lease out to the client. It then adds the MAC address information of the client and the IP address it will lease out to the ARP table. When this is done, the server sends this information to the client as a DHCPOFFER message.

3.Selection

DHCP client chooses IP address. There may be several DHCP servers sending DHCP-Offer packet, the client only receives the first DHCP-Offer then sends back DHCP-Request packet in broadcast mode to all DHCP servers to request more information on the IP address lease time and verification. The packet includes the contents of the IP address requested from the selected DHCP server.

4.Acknowledge

When the DHCP server receives a DHCP-Request packet from the DHCP client, it confirms the lease and creates a new ARP mapping with the IP address it assigned to the client and the client’s MAC address. And then send this message as a unicast to the client as a DHCPACK.

How to Configure DHCP for Multiple VLANs?

The theory cannot be well digested unless it is combined with the practice. In this section, how to configure DHCP for multiple VLANs is introduced for your reference. Take the following picture as an example.

DHCP configuration

Fig 2. DHCP Configuration for Multiple VLANs

PC1 and PC2 are connected to access port of VLAN switch 1 with VLAN ID 100 and 200.

The DHCP server was supposed to serve both the VLANs.

Command to enable multiple VLANs.

DHCP configuration 1

Command to enable DHCP.

DHCP configuration 2

Add both subnets.

DHCP configuration 3

Run DHCP server.

DHCP configuration 4

Now make PC1 and PC2 as DHCP client. Both should be able to get IP address from DHCP server in their respective VLAN.

Conclusion

How to configure DHCP for multiple VLANs? This issue has been illustrated in the above content. DHCP configuration is worthy of being learned by those who are engaged in fiber optic communication field. You just need to know “How”, and let FS provide you with the best network devices. Ethernet switch like gigabit Ethernet switch and 10gbe switch, and routers are available in FS.

Core Switch Vs Distribution Switch Vs Access Switch

The hierarchical internetworking model defined by Cisco includes core layer, distribution layer and access layer. Therefore, the network switches working in these layers get corresponding names like core switch, distribution switch and access switch. This post mainly explores the confusing problem: core switch vs distribution switch vs access switch.

Definition: Core Switch Vs Distribution Switch Vs Access Switch

What Is Core Switch?

Core switch is not a certain kind of network switch. It refers to the data switch that is positioned at the backbone or physical core of a network. Therefore, it must be a high-capacity switch so as to serve as the gateway to a wide area network (WAN) or the Internet. In a word, it provides the final aggregation point for the network and allows various aggregation modules to work together.

What Is Distribution Switch?

Similarly, the distribution switch lies in distribution layer, and it links upwards to layer core switch and downwards to the access switch. It is also called aggregation switch which functions as a bridge between core layer switch and access layer switch. In addition, distribution switch ensures that the packets are appropriately routed between subnets and VLANs in enterprise network. 10gb switch usually can perform as a distribution switch.

What Is Access Switch?

Access switch generally locates at the access layer for connecting the majority of devices to the network, therefore it usually has high-density ports. It is the most commonly-used gigabit Ethernet switch which communicates directly with the public Internet, mostly used in offices, small server rooms, and media production centers. Both managed and unmanaged switches can be deployed as access layer switch.

core switch vs distribution switch vs access switch

Figure 1: core switch vs distribution switch vs access switch

Comparison: Core Switch Vs Distribution Switch Vs Access Switch

The switches may co-exist in the same network, and coordinate with each other to contribute to an unrestricted network speed with each layer switch performing its own duty. Well, what’s the difference: core switch vs distribution switch vs access switch?

Core Switch Vs Distribution Switch

Core switch has the higher reliability, functionality and throughput than distribution switch. The former one aims at routing and forwarding, and provides optimized and reliable backbone transmission structure, while the latter one functions as the unified exit for access node, and may also do routing and forwarding. The distribution switch must has large enough capacity to process all traffic from the access devices. What’s more, there’s generally only one (or two for redundancy) core switch used in a small and midsize network, but multiple distribution switches in distribution or aggregation layer.

Core Switch Vs Access Switch

The lower levels the switch dwells in, the more devices it connects to. Therefore, a big gap of ports number exists in access switch and core switch. Most access switches need to connect various end user equipment ranging from IP phone, to PCs, cameras etc,. While the core switch may be just linked with several distribution switches. Meanwhile, the higher layer the switch lies in, the faster port speed it requires. Access switch is to core switch what river is to the ocean, as the latter one has the large throughput to receive the data packets from the former one. Most modern access switches come with a 10/100/1000Mbps copper ports. An example of this is FS S2800-24T4F 24 port 100/1000BASE-T copper gigabit Ethernet switch. While core switches commonly have 10Gbps and 100Gbps fiber optic ports.

Distribution Switch Vs Access Switch

As access switch is the one that allows your devices to connect the network, it undoubtedly supports port security, VLANs, Fast Ethernet/Gigabit Ethernet and etc. Distribution switch which is mainly responsible for routing and policy-based network connectivity supports additional higher performance like packet filtering, QoS, and application gateways. All in all, access switch is usually a layer 2 switch and distribution switch is a layer 3 switch. When multiple access switches among different VLANs are required to be aggregated, a distribution switch can achieve inter-VLAN communication.

Conclusion

What’s the difference: core switch vs distribution switch vs access switch. To sum up, the access switch facilitates devices to the network. The distribution switch accepts traffic from all the access layer switches and supports more high-end features. And the core switch is responsible for routing and forwarding at the highest level. FS provides different types of Ethernet switches that can work as core switches, distribution switch or access switches. For more details, please visit www.fs.com.

Get Further Understanding of Ethernet Switch Port Types

Have you ever noticed the ports on your gigabit PoE switch or other network switches? They may come in different port types and work on different switch port modes. The switch ports number varies from different network switches and port type can be configured according to specific needs. Then how many ports on a switch? What are the common switch port types?

How Many Ports Does a Network Switch Have?

Generally, I’d like to assort the ports on the switch into the ones that enable others to work and the ones to realize its own operation. The former may be classified into different types of ports based on their port speeds as shown in the following diagram, and the latter is referred to the console port. Almost every switch has a console port used to connect to the computer and manage the switch as the switch has no display component.

Here takes FS gigabit switch, 10GB Ethernet switch and 40G/100G Ethernet switches as examples to show the switch port types and numbers that a network switch may have.

S3800-24T4S
1GB Ethernet Switch
S5800-8TF12S
10GB Ethernet Switch
S5850-48T4Q
40GB Ethernet Switch
S5850-48S2Q4C
100GB Ethernet Switch
RJ45 port
8
8
48
/
SFP port
8
8
/
48
SFP+ port
12
12
/
/
QSFP+ port
/
/
4
2
QSFP28 port
/
/
/
4

As the above figure shows, a network switch may support diversified ports. The common port number of FS network switch is 8, 24 and 48. While the maximum number of ports in a switch can grow as demands.

Common Switch Port Types on Network Switches

When the data switch resides in a VLAN, there may be three common switch port types: access port, trunk port and hybrid port. An Ethernet interface can function as a trunk port, an access port or a hybrid port.

Switch Port Types: Access Port

Access port is used for connecting devices such as desktops, laptops, printers etc., only available in access link. A switch port in access modes belongs to one specific VLAN and sends and receives regular Ethernet frames in untagged form. Usually, an access port can only be member of one VLAN, namely the access VLAN, and it discards all frames that are not classified to the access VLAN.

Switch Port Types: Trunk Port

Trunk port is adopted among switches or between switch and upper-level devices, available in trunk link. A trunk port allows for several VLANs set up on the interface. As a result, it is able to carry traffic for numerous VLANs at the same time. Frames are marked with unique identifying tags—either 802.1Q tags or Interswitch Link (ISL) tags—when they move between switches through trunk ports. Therefore, every single frame can be directed to its designated VLAN. The trunk port is a VLAN aggregation port connected to other switch ports while the access port is the port that the switch connects to the host in the VLAN. The following picture shows their differences.

switch port types: trunk port vs. access port

Switch Port Types: Hybrid Port

Hybrid ports can be used to connect network devices, as well as user devices. It supports both untagged VLAN like access port and tagged VLAN like trunk port, and it can receive data from one or more VLANs. The hybrid ports resemble trunk ports in many ways, but they have additional port configuration features. Hybrid port can send some packets without tag to PC or IP phone, and others packets with tag to other device which can process tag.

Conclusion

Knowing the switch ports number can help you select the right switch for you. And figuring out the switch port types helps you configure your switch ports accordingly. This post introduces the three basic switch port types and their differences. Hope it will be helpful for you.

Ethernet Switch with 10Gb Uplink or 1Gb Uplink

With the booming high speed broadband technology, modern Ethernet switch has stretched its branches to SMB operators and even home individuals. The exclusive property of network switch to big enterprises no longer exists. Accordingly questions about the uplink ports on Ethernet switch has put forward by lots of newbies. What is uplink on Ethernet switch? What is the function of 10Gb uplink on gigabit switch? For a specific home or SMB usage, should I employ network switch with 10Gb uplink or 1Gb uplink? With concerns of a reliable backbone, should I upgrade to gigabit access switch with 10G uplink to core 10GbE switch? For anyone with doubts about Ethernet switch with 10Gb uplink vs 1Gb uplink, this article may help.

Understanding Uplink Port on Ethernet Switch

Uplink port on Ethernet switch serves as different layer network connection, which enables a lower network to link up to a higher network. One also uses it as regular port to connect end users while link aggregation is not involved. Connecting the uplink port on one access Ethernet switch to the regular port on another higher-layer core switch enables bandwidth expansion. The uplink bandwidth will be shared by all the end devices connected to the access switch regular ports. For example, by putting a 10Gb uplink on a 1Gb Ethernet switch, it would let 10 devices on the switch communicate at 1Gb each at the same time with the rest of the network. Otherwise if the uplink was only 1Gb, those 10 devices would only be able to get about 100Mb each.

Ethernet Switch with 10Gb Uplink

10Gb uplink is commonly built in 1Gb access Ethernet switch for 10G link aggregation. Thus gigabit switch with 10Gb uplink is also called as 10GbE switch by many users. In the market such Ethernet switches with 10Gb uplinks are available for copper and optical SFP switch with 2/4 uplinks. For instance, FS provides 4 SFP+ 10Gb uplinks on 24/48-port 1000Base-T RJ45/SFP managed gigabit switches such as S3800 series 24-port stackable 1000Base-T/SFP Ethernet switches.

Some vendors like FS.COM also bring in PoE to 10Gb uplink switch for advanced features. Say S1600-48T4S 48-port PoE+ managed gigabit switch. It can boost your network to a switching capacity of 180Gbps and offers 600W total power budget for power-hungry PDs. Such Ethernet switches with 10Gb uplinks frequently used as access layer switches to link up to backbone core 10GbE switch. Then all end users on the gigabit switch can share the 10Gb bandwidth, not 1Gb anymore.

Ethernet switch with 10Gb uplink application

Figure 1: Deploying FS 48-port Ethernet switches with 4 SFP+ 10Gb uplinks ports as access switches to connect 10Gb core switch in data center layer.

Ethernet Switch with 1Gb Uplink

Only a few years ago 100Mb Ethernet switch are still common among many SMBs as access switch. However, nowadays it has gradually obsoleted by 100/1000MBase gigabit switch. To enhance network connection resiliency, modern gigabit switch comes with 24/48 RJ45 100/1000Base-T ports and 4 1Gb SFP ports for uplink. Except uplink function, The SFP uplinks on copper gigabit Ethernet switch provides optical link option when the network requires fiber cabling. FS supplies such SFP uplinks on 8/24- port PoE+ managed gigabit switch with different power budget for 1G speed.

FS PoE gigabit Ethernet switch with SFP 1Gb uplink

Figure 2: FS PoE+ Ethernet switches with SFP 1Gb uplinks and  PoE+ switch with SFP+ 10Gb uplinks are natural fit for IP cameras, VoIP phones and wireless APs.

Ethernet Switch with 10Gb Uplink or 1Gb Uplink Selection Guide

So how to choose from 10Gb and 1Gb uplink of Ethernet switch? Try to ask yourself about questions as follows. What kind of application virtualization are you implementing? How many users are there? Whether the applications and user quantity requiring for the extra bandwidth of 10Gbps? Is my cabling up-to-snuff for 10Gb uplink? Can I afford 10Gb Ethernet?

Then here are some suggestions for you. First, attach importance to applications virtualization. If your employees only need to open occasional Word documents, reply to emails or update database records, there would not be much of a requirement for 10G uplink on Ethernet switch. But if you should do lots of mass data transfer such as photos and videos exchange even in a small advertising shop it would quite be another story. Second, concern about number of users. The proliferating wireless APs and office devices bring much burdens to your network. Third, for concerns of future-proof expansion and a reliable backbone, even if your current 1GbE is unsaturated, Ethernet switch with 10Gb uplinks is also a good solution for enterprises with hardware upgrading demands. But if the aforesaid factors not concerned, your gigabit Ethernet switch with 1Gb uplink may suit your network just fine.

Conclusion

Both 10Gb uplink and 1Gb uplink on Ethernet switch are designed for link aggregation of multi-layer switch connection. Ethernet gigabit switch with 10Gb uplink enables total 10Gbps bandwidth to divide to end devices for accessing max. 1G speed. While Ethernet switch with 1Gb uplink delivers max. 100Mbps data rate to 10 devices. For concerns of high bandwidth applications, multiple office devices quantity and future-proof expansion, Ethernet switch with 10Gb uplink is the way to go. Otherwise your existing gigabit switch with 1Gb uplink can make sense.