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9300m series VLAN tagging

Joel Belizario
Trusted Contributor

9300m series VLAN tagging

Hi everyone,

Trying to resolve an issue at the customer's site, they have a 9315m switch and running VMware ESX on some hosts. At this stage we are trying to figure out what is causing the lack of connectivity, whether it is a VMware issue or VLAN tagging on the 9315m.

This is what they are trying to accomplish:

One physical host with 3 virtual servers with corresponding VLANs setup.

Server A - 192.168.1.x (VLAN 1)
Server B - 192.168.2.x (VLAN 2)
Server C - 192.168.3.x (VLAN 3)

The ethernet port on the 9315m is a tagged member of all 3 VLANs and is not untagged in any VLAN (I can't remember if this is the behaviour of the 9300 switches? I looked up documentation but haven't found where it explicitly states this).

The issue is that two of the servers work perfectly fine but the 3rd server does not have connectivity and is unable to ping anything within VLAN 3.

We have analysed all settings on both VMware and the 9315m but have been unable to come to a conclusion what is causing this. Can anyone offer any advice on this?

Thanks in advance, points awarded for all feedback!
Matt Hobbs
Honored Contributor

Re: 9300m series VLAN tagging

With the 9300's, unless you use the 'dual-mode' command on a port then all VLANs will be tagged.

Since 2 out of 3 virtual servers work then it seems like there is something wrong with that 3rd servers configuration or the VLAN settings for that VLAN.

That's all I've got for now...
Mohieddin Kharnoub
Honored Contributor

Re: 9300m series VLAN tagging


Dual-Mode is used only in order to carry both tagged and untagged traffic on the same link.

By default, a dual-mode port assigns untagged
traffic to the default_vlan (1).

If you need this port to be untagged to the default_vlan then you should run the dual-mode command.

However, you can assign untagged traffic to any VLAN by specifying a vlan id in the dual-mode command, example: dual-mode 3 would ensure that untagged traffic was assigned to vlan 3.

I think what you do is: from the server check the configuration then try to reach its gateway if you have routing on the 9300.

Good Luck !!!
Science for Everyone
Trusted Contributor

Re: 9300m series VLAN tagging

Server C is unable to ping hosts in its own VLAN? Server A or B is unable to ping hosts in subnet? Do you have this situation with other hosts attached to other ports on your 9315m?
Joel Belizario
Trusted Contributor

Re: 9300m series VLAN tagging

Ok for some strange reason when we put the server in another VLAN it will work without any issues, it is only in VLAN 3 that it will not work.

We have double and triple checked all the configs and another host in VLAN 3 works fine.

I guess the only explanation is something weird is going on in that VMware server but we are unable to pinpoint the issue or rebuild it as a troubleshooting step.