VLAN – VLAN Tagging Between Linux and Cisco Small Business Switches: Fluke, Bug, or Misconfiguration?

ciscolinuxtrunkvlan

I seem to be having trouble with communications between a Ubuntu 16.04 VM and Cisco SG-300 10 port switch. I feel like there is something obvious I MUST be missing but for the life of me I cannot figure it out.

On the Linux side, the relevant commands entered are:

modprobe 8021q   
sudo vconfig ens34 3700   
sudo ip addr add 10.0.0.1/24 dev ens34.3700  
sudo ip link set up ens34.3700

On the Cisco side, relevant commands entered are (starting from default config):

config terminal  
interface ge 1  
switchport mode trunk  
switchport trunk allowed vlan add 3700  
exit  
interface vlan3700  
ip add 10.0.0.2 255.255.255.0  
no shutdown

Yet for some reason I cannot ping between the VM and the switch.

I used Wireshark to capture some traffic between the two, and what I notice is that the frames VM –> Cisco switch are all tagged VLAN 3700, and the Cisco switch is able to read these frames and respond, however the responses seem to be untagged.

Linux–>Cisco

Cisco–>Linux

Why does this happen? What can I do to fix it?

Best Answer

I never really figured this out but I've moved on from it and chalked it up to the vlan linux package lacking some intelligence that Cisco has. (seeing as how Cisco understood when packets were meant for it and Linux didn't)

Thanks to all who took time for this.

Related Solutions

Vlan – Setting up PIM Sparse mode

My questions are:

Should we setup on our core network switch OSPF with a router ID of 1.1.1.1 and then not set any OSPF settings on any other switch?

OSPF is not necessary for this implementation.

Would PIM Sparse Mode only need to be enabled on the core switches or on all of the switches in the network?

Pim-SM needs to be enabled on each L3 interface on which you want to allow the multicast traffic. For example, if you wish to contain the traffic to Vlans 15 and 14, you would have to do the following on your core:

configure
ip multicast
ip igmp
ip pim sparse
interface vlan 14
ip igmp
ip pim
interface vlan 15
ip igmp
ip pim
exit

If you want the traffic to traverse all Vlans, then you will need the appropriate interface configuration under each Vlan. Your L2 switches will need IGMP snooping turned on (ideally on all interfaces via the global configuration).

configure
ip igmp snooping 
bridge multicast filtering

For a very basic multicast setup like this, these should be the only features that you would need.

Cisco 200 series switches with SonicWALL NSA 4600 setting up VLAN

Okay, a bunch of answers. Here we go:

For the VoIP VLAN - will the PCs be sharing the switch ports on the back of the phone? If so, you'll need to set the switch ports as tagged trunk ports, and configure the phone for the VLAN. Otherwise, you can do as you stated. The phones will connect to the switch on untagged access ports. The ports between switches and to the SonicWALL will be tagged trunk ports.

For the SonicWALL, you'll create a separate zone for each VLAN. Configure the VLAN interfaces with the proper VLAN ID, and it should work (as long as the SonicWALL is plugged into a tagged trunk port.

Give it a shot and let us know if you run into any problems.

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