How to configure vlan

How to configure vlan

VLAN (Virtual Local Area Network) 

Objective 

A VLAN (Virtual Local Area Network) allows network administrators to logically segment Layer 2 broadcast domains within a switch or across multiple switches. This segmentation is independent of the physical topology, meaning devices can belong to the same VLAN even if they are connected to different physical switches. By isolating traffic between different VLANs, organizations can improve security (by restricting broadcast domains), network performance (by reducing broadcast traffic), and manageability (by grouping users or services logically rather than physically). 

Prerequisites 

Hardware: 

  • Switches or routers that support VLANs 
     (e.g., edgecore, ufispace) 

Software: 

  • Network operating systems that support VLAN configuration 
     (e.g., SONiC.master ) 

Access: 

  • Administrative or privileged CLI access 

Network: 

  • Knowledge of VLAN ID range (1–4094) 

  • Identified interfaces to assign to each VLAN 

  • VLAN design document outlining VLAN IDs, names, and purposes 

 

TOPOLOGY: 

 

 
  

Configuration commands (sonic configurations): 

Note 1: Commands are to be executed in sudo mode  

Note 2: SW1 is only for sending traffic 

Step 1: Create vlan and vlan member for interface 

SW2 : 

 

config vlan add 30 

config vlan member add -u 30 Ethernet2 

config vlan member add -u 30 Ethernet20 

 

SW3: 

config vlan add 30 
config vlan member add -u 30 Ethernet2 

config vlan member add -u 30 Ethernet20 

 

For tagged port 

config vlan member add 30 Ethernet3 

 

VALIDATION (SONIC SHOW OUTPUTS) 

root@sonic:/home/admin# show vlan brief 

+-----------+--------------+------------+----------------+-----------------------+-------------+ 

|   VLAN ID | IP Address   | Ports      | Port Tagging   | DHCP Helper Address   | Proxy ARP   | 

+===========+==============+============+================+=======================+=============+ 

|        30 |              | Ethernet2  | untagged       |                       | disabled    | 

|           |              | Ethernet3  | tagged         |                       |             | 

|           |              | Ethernet20 | untagged       |                       |             | 

+-----------+--------------+------------+----------------+-----------------------+-------------+ 

 

 

 

root@sonic:/home/admin# show vlan config 

Name      VID  Member      Mode 

------  -----  ----------  -------- 

Vlan30     30  Ethernet2   untagged 

Vlan30     30  Ethernet3   tagged 

Vlan30     30  Ethernet20  untagged 

root@sonic:/home/admin# sudo bridge vlan 

port    vlan ids 

docker0  1 PVID Egress Untagged 

 Bridge   30 

 dummy    1 PVID Egress Untagged 

 Ethernet2        30 PVID Egress Untagged 

 Ethernet3        30 

 Ethernet20       30 PVID Egress Untagged 

 

 

 

root@sonic:/home/admin# tcpdump -nei Ethernet8 

tcpdump: verbose output suppressed, use -v[v]... for full protocol decode 

listening on Ethernet8, link-type EN10MB (Ethernet), snapshot length 262144 bytes 

21:22:24.682967 a8:2b:b5:17:d2:58 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 285: LLDP, length 271: sonic.PALCNETWORKS.COM 

21:22:25.483609 68:21:5f:9c:fc:7b > 01:80:c2:00:00:0e, ethertype 802.1Q (0x8100), length 271: vlan 30, p 0, ethertype LLDP (0x88cc), LLDP, length 253: sonic 

21:22:54.691258 a8:2b:b5:17:d2:58 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 285: LLDP, length 271: sonic.PALCNETWORKS.COM 

21:22:55.490589 68:21:5f:9c:fc:7b > 01:80:c2:00:00:0e, ethertype 802.1Q (0x8100), length 271: vlan 30, p 0, ethertype LLDP (0x88cc), LLDP, length 253: sonic 

21:23:24.694718 a8:2b:b5:17:d2:58 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 285: LLDP, length 271: sonic.PALCNETWORKS.COM 

21:23:25.497841 68:21:5f:9c:fc:7b > 01:80:c2:00:00:0e, ethertype 802.1Q (0x8100), length 271: vlan 30, p 0, ethertype LLDP (0x88cc), LLDP, length 253: sonic 

21:23:54.702364 a8:2b:b5:17:d2:58 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 285: LLDP, length 271: sonic.PALCNETWORKS.COM 

21:23:55.501700 68:21:5f:9c:fc:7b > 01:80:c2:00:00:0e, ethertype 802.1Q (0x8100), length 271: vlan 30, p 0, ethertype LLDP (0x88cc), LLDP, length 253: sonic 

21:24:24.704748 a8:2b:b5:17:d2:58 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 285: LLDP, length 271: sonic.PALCNETWORKS.COM 

21:24:25.505631 68:21:5f:9c:fc:7b > 01:80:c2:00:00:0e, ethertype 802.1Q (0x8100), length 271: vlan 30, p 0, ethertype LLDP (0x88cc), LLDP, length 253: sonic 

21:24:54.708163 a8:2b:b5:17:d2:58 > 01:80:c2:00:00:0e, ethertype LLDP (0x88cc), length 285: LLDP, length 271: sonic.PALCNETWORKS.COM 

21:24:55.509209 68:21:5f:9c:fc:7b > 01:80:c2:00:00:0e, ethertype 802.1Q (0x8100), length 271: vlan 30, p 0, ethertype LLDP (0x88cc), LLDP, length 253: sonic 

 

  

 

root@sonic:/home/admin# tcpdump -nei Ethernet8 -xxx 

tcpdump: verbose output suppressed, use -v[v]... for full protocol decode 

listening on Ethernet8, link-type EN10MB (Ethernet), snapshot length 262144 bytes 

21:29:15.103412 00:03:05:03:04:05 > 00:01:02:03:04:05, ethertype 802.1Q (0x8100), length 64: vlan 30, p 0, 802.3 [|llc] 

        0x0000:  0001 0203 0405 0003 0503 0405 8100 001e 

        0x0010:  0000 0000 0000 0000 0000 0000 0000 0000 

        0x0020:  0000 0000 0000 0000 0000 0000 0000 0000 

        0x0030:  0000 0000 0000 0000 0000 0000 0000 0000 

21:29:15.131325 00:03:05:03:04:05 > 00:01:02:03:04:05, ethertype 802.1Q (0x8100), length 64: vlan 30, p 0, 802.3 [|llc] 

        0x0000:  0001 0203 0405 0003 0503 0405 8100 001e 

        0x0010:  0000 0000 0000 0000 0000 0000 0000 0000 

        0x0020:  0000 0000 0000 0000 0000 0000 0000 0000 

        0x0030:  0000 0000 0000 0000 0000 0000 0000 0000