Inter VLAN routing configuration is a necessary operation for devices in VLAN to communicate and transmit data to each other. In the article below, DNG Corp will guide you through the steps to configure Inter-VLAN Switch Layer 3 routing easily and quickly.
What is Inter VLAN Switch Layer 3?
Before going into the routing configuration instructions, DNG Corp will summarize the information so that readers can better understand what Inter VLAN Switch Layer 3 is?
Normally, routers (also known as routers) are used to divide broadcast domains and switches (switches) at layer 2. Although operating in a single broadcast domain, switches can also divide broadcast domains using VLANs (Virtual LANs).
VLANs are understood as logical network groups of devices in a broadcast domain (which may or may not be in the same broadcast domain). Furthermore, all switch ports are in VLAN 1 by default. Since a single broadcast domain is divided into multiple broadcast domains, routers or Layer 3 Switches are used to perform the task of communication between different VLANs. This process of communication between different VLANs is called Inter VLAN Routing.
What is Inter VLAN Switch Layer 3 Routing?
Suppose, we have created 2 logical device groups (VLANs) named “Sales” and “Finance”. In case a device of the “Sales” department wants to communicate with a device in the “Finance” department, we are required to route Inter VLAN. This routing will be done by a router or Layer 3 Switch. Thus, it can be understood that Inter VLAN Switch Layer 3 is the routing of inter VLANs using a Layer 3 Switch device.
Advantages of VLAN routing using Layer 3 Switch
VLAN routing using Layer 3 Switch plays an important role in the process of connecting network systems in enterprises due to the following outstanding advantages:
- Increased routing speed: Inter VLAN routing using Layer 3 Switch is faster than other routing methods. Because Layer 3 Switch can perform the routing process quickly without any intervention from other external routers.
- Cost-effective: Using Layer 3 Switch for Inter VLAN routing saves costs instead of using a separate router. This method eliminates the need for an external router and its associated costs.
- Provides scalability: Inter VLAN layer 3 switches are scalable, as additional VLANs can be easily added without requiring major changes to the network topology.
- Ensures security: This inter VLAN routing method provides better security. This is because users are allowed to create access control lists (ACLs) to restrict traffic between VLANs.
Disadvantages of using
Although the method of configuring Inter VLAN routing using Layer 3 Switch has many outstanding advantages, it also has disadvantages that need to be overcome as follows:
Complicated implementation: Configuring and managing Inter VLAN routing using Layer 3 Switch will be complicated in large network systems with many VLANs.
Limited functionality: Compared to using a dedicated router, this method will have more limitations, typically the routing options available to the network administrator.
Single point of failure: If the Layer 3 Switch fails to route, all traffic between VLANs will also be interrupted. This will cause significant network downtime.
Increased bandwidth usage: Inter VLAN Switch Layer 3 can lead to increased bandwidth usage, as all traffic between VLANs will have to go through the Layer 3 Switch. If not managed properly, it will cause network congestion.
=> See more: Detailed instructions on how to configure L3 Mobility Aruba IAP
Techniques in Inter – VLAN routing
Some techniques in Inter VLAN routing configuration:
Legacy Inter – VLAN routing
With this technique, the SVI will be created with the corresponding VLAN, acting as a default gateway for that VLAN. This is like creating a sub-interface of the router in the router on a stick process.
If the data packet is sent to different VLANs, it means that Inter VLAN routing is performed on the Layer 3 Switch. At this time, the data packet will be transferred to the L3 Switch and then transferred to the destination, similar to the router on a stick process.
Kỹ thuật Legacy Inter-VLAN Routing
Router-on-a-stick
Router-on-a-stick technique is that the user will use a physical port of the router and then divide it into Interfaces with independent logic (Subinterface). At this time, a physical port is divided into stable ports, each port performs the task of a default port for the corresponding VLANs.
This technique is applied to most Switch lines, simple configuration, saving expansion ports.
However, when using this method, the traffic of the VLANs must share the trunking connection. If this trunking line is congested, the VLANs will also be affected, increasing the delay. The reason is because the data packets must leave the Switches, enter the router and then return to the Switch, at the same time, the Router uses soft switching.
Switch virtual interfaces (SVIs)
SVI is a logical interface on a multilayer switch that provides layer 3 processing for data packets to all switch ports associated with a VLAN. Only one SVI is created for a VLAN.
This technique provides all management and routing services, while SVI on Layer 2 Switches only provides management services such as VLAN creation or Telnet/SSH services. Layer 3 Switches fully inherit the functions of Layer 2, and have higher speeds. In addition, the built-in intelligent IP routing table allows connecting LAN or VLAN ranges. In the same network system, Layer 3 Switches allow superior processing compared to Layer 2, operating more stably without the help of a router. It can be seen that this is the most optimal method to ensure fast and reliable routing.
Not only that, when combining this method with Etherchannel technology, it will increase transmission speed and availability much higher.
Instructions for deploying Auto-configuration inter-vlan routing
Steps for deploying auto-configuration inter-vlan routing for Layer 3 Switch:
Step 1: Configure ssh for Router
R1(config)#ip domain-name bkap.edu.vn
R1(config)#username admin password bkap
R1(config)#username admin privi 15
R1(config)#line vty 0 4
R1(config-line)#transport input ssh
R1(config-line)#login local
R1(config-line)#exit
R1(config)#crypto key generate rsa modulus 1024
Step 2: Configure telnet for layer 3 switch
DLS(config)#username admin password bkap
DLS(config)#username admin privi 15
DLS(config)#line vty 0 4
DLS(config-line)#transport input telnet
DLS(config-line)#login local
DLS(config-line)#exit
Step 3: Verify
Perform Verify from Admin SSH/Telnet to R1 and DLS
Step 3 guide to configure Inter VLAN routing
Step 4: Prepare the document containing the commands to be executed for R1
int e0/1
no shutdown
int e0/1.10
encapsulation dot1Q 10
ip add 192.168.10.1 255.255.255.0
ip route 192.168.20.0 255.255.255.0 192.168.122.118
Step 5: Prepare the document containing the commands to be executed for DLS
Config terminal
vlan 20
name DLS
int vlan 20
no shutdown
ip add 192.168.20.1 255.255.255.0
ip routing
ip route 192.168.10.0 255.255.255.0 192.168.122.190 int e0/1 sw mode access sw access vlan 20 sw port-security sw port-security max 2 sw port-security mac sticky sw port-security violation restrict
Step 6: Write configuration setup script import getpass import telnetlib from netmiko import
ConnectHandler Router_R1 = { ‘device_type’: ‘cisco_ios’, ‘ip’: ’19 2.168.122.190′, ‘username’: ‘admin’, ‘password’: ‘123’, } with open(‘R1’) as f: lines = f.read().splitlines() net_connect = ConnectHandler(**Router_R1) output = net_connect.send_config_set(lines) print (output) HOST = “192.168.122.118” user = input(“Enter your telnet username: “) password = getpass.getpass() tn = telnetlib.Telnet(HOST) tn.read_until(b”Username: “) tn.write(user.encode(‘ascii’) + b”\n”) if password: tn.read_until( b”Password: “) tn.write(password.encode(‘ascii’) + b”\n”) with open(‘DLS’) as f: lines = f.read().splitlines() print(lines) for i in lines: tn.write(i.encode(‘ascii’) + b”\n”)
tn.write(b”end\n”)
tn.write(b”exit\n”)
print(tn.read_all().decode(‘ascii’))
Step 7: Run the script and check the results
Step 7 guide to configure Inter VLAN Switch Layer 3 routing
Results received:
Results obtained after configuring Inter VLAN Switch L3 routing
These are all the steps to configure Inter VLAN Switch Layer 3 routing that DNG Corp informs you.
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