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GS308E Smart Managed Plus VLAN

jpbears1
Aspirant

GS308E Smart Managed Plus VLAN

I have a question about VLAN operation for the "Smart Managed Plus" switch line.

 

One primary purpose of a switch is that it will learn about what connected devices are on each switch port and send unicast traffic destined to a device only to the port its connected to. This is a fundamental difference between a switch and the older hubs.

 

When enabling 802.1q VLAN on the Smart Managed Plus switches - it seems this line of switches stops acting like a switch and more like a hub.

 

If I configure 3 VLANs (VLAN 10, 20, 30) and let's say we configure ports 1, 2, 3 to be untagged members of VLAN 10, port 1 & 2 to be untagged member of VLAN 20 and ports 1 & 3 to be untagged members of VLAN 30.  Port 1 VID will be 10; port 2 VID will be 20; and port 3 VID will be 30.  All ingress traffic on port 1 'could' egress port 2 & 3.  All ingress traffic on port 2 'could' egress could egress port 1. All ingress traffic on port 3 'could' egress port 1.  Ports 2 & 3 should be isolated from each other.

 

However, if you capture traffic on port 2 you will see unicast traffic destined for devices on port 3.  If you capture traffic on port 3 you will see unicast traffic destined for port 2.  Its almost like the switching table learning capability isn't working anymore and it simply forwards all ingress traffic on port 1 to both port 2 and 3 no matter what.  If a packet ingress port 1 destined for a device on port 2, the switch should learn that device is on port 2 and not forward to 3.

 

This behavior isn't seen on other switches.

Model: GS308E|8 Port Gigabit Ethernet Smart Managed Plus Switch
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schumaku
Guru

Re: GS308E Smart Managed Plus VLAN

Asymmetric VLANs are by far not supported by all 802.1Q supporting switches - because asymmetric (sometimes named overlapping) is not a part of the 802.1Q standard at all. Some vendors misleadingly designate 802.1Q == Asymmetric VLAN ... what is definitively wrong.

In my opinion it's a mistake that the Netgear Web UI does allow such a configuration, because Netgear does strictly support using routing for any connection between different VLANs only, certainly in the Smart Managed Plus and Smart Managed Pro switch class (and when I have it right even in the Manages Switch class). The hub-like behavior is a side effect of the invalid configuration applied to the switch core IMHO.

VLANs as per 802.1Q allow network administrators to subdivide a physical network into separate logical broadcast domains. On a flat Layer 2 network, all hosts connected to a switch are members of the same broadcast domain; and broadcast domains and IP subnet can only be interconnected by routers.

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schumaku
Guru

Re: GS308E Smart Managed Plus VLAN

Asymmetric VLANs are by far not supported by all 802.1Q supporting switches - because asymmetric (sometimes named overlapping) is not a part of the 802.1Q standard at all. Some vendors misleadingly designate 802.1Q == Asymmetric VLAN ... what is definitively wrong.

In my opinion it's a mistake that the Netgear Web UI does allow such a configuration, because Netgear does strictly support using routing for any connection between different VLANs only, certainly in the Smart Managed Plus and Smart Managed Pro switch class (and when I have it right even in the Manages Switch class). The hub-like behavior is a side effect of the invalid configuration applied to the switch core IMHO.

VLANs as per 802.1Q allow network administrators to subdivide a physical network into separate logical broadcast domains. On a flat Layer 2 network, all hosts connected to a switch are members of the same broadcast domain; and broadcast domains and IP subnet can only be interconnected by routers.

View solution in original post

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jpbears1
Aspirant

Re: GS308E Smart Managed Plus VLAN

Thanks this makes sense!

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