Same VLAN on two switches (S3300's) will not communicate

[rand__]

Hi,

probably its just a stupidity issue on my side but I can't get this to work.

I am trying to get two boxes to communicate over two switches using a particular vlan. This is actually the simplified solution attempt for a more complex issue but can't even get this to work:(

I've been following https://kb.netgear.com/11673/How-do-I-setup-a-VLAN-trunk-link-between-two-NETGEAR-switches this guide.

Test Setup :

2x S3300 (one on 6.6.14, one one .17) connected via Trunk

1x ESX box with a vSwitch with multiple vmknics, one of these on the relvant vlan (6)

1x Windows Box (no VLAN setup on nic)

Switch A (stacked with another S3300)

Interface    PVID    VLAN Member    VLAN Tag    Acceptable Frame    Untagged VLANs    Tagged VLANs    Comment
2/g14            6        6                       None            Admit All                    6                            None       TestPort Local Switch
2/xg25          1        1,6                    6                   Admit All                     1                            6                         Trunk Link
2/xg28          1        1,5-9,18,19       5-9,18,19     Admit All                     1                            5-9,18,19             ESX Box

ESX box with a vmknic on VLAN 6 on Switch A, Trunk configured on 25 according to KB.

14 is a testport - if I connect the Windows box to this port the connection works (- - > Intra Switch VLAN is fine)

Switch B

Interface    PVID    VLAN Member    VLAN Tag    Acceptable Frame    Untagged VLANs    Tagged VLANs    Comment
1/g22         6          6                        None           Admit All                     6                            None                  Windows Box
1/g23         1          1,6                     6                 Admit All                     1                            6                          Trunk Link

If the Windows Box is connected to B/22 I can't communicate with it and I can't see why not

I have tried a lot of things already, setting up VLAN IPs for example on both switches to check whether its a port issue or not. But its always the same pattern - everything local is working fine but as soon as the traffic has to flow to the other switch its not.

Everything on VLAN 1 is working fine o/c, just not on another VLAN.

Looking for any kind of clue, totally lost 😞

Thanks for reading.

[JohnC_V · Accepted solution]

@rand__,

That's correct. Functionality of VLANs is to separate the actual/physical networks. VLANs also have a default gateway even if it is set to static and even if they are working on the same subnet. You should have a default gateway(router) configured if not the traffic will not route across the network. Have you tried the setup that I suggested? That is also how VLAN works even if you use different switches. Every network has its own default gateway even if we are not talking about VLANs.

Regards,

[JohnC_V]

Hi rand__,

Welcome to the community!

It seems that we need to pass VLAN 6 on both switches and I notice that you don't have a trunk going to your firewall/router that will provide dhcp or default gateway for VLAN 6 devices. You may try this setup:

e.g.
Switch A
g1 - T (VLAN 6) - PVID 1 - goes to Switch B
g2 - T (VLAN 6) - PVID 1 - goes to Firewall/Router(it should have VLAN 6 and the port should be set as trunk)

Switch B
g1 - T (VLAN 6) - PVID 1 - goes to Switch A
g2 - U (VLAN 6) - PVID 6 - goes to the Windows Box

Basically, VLAN aware devices should be set as T and for non-VLAN aware devices should be set as U then specify the PVID.

You may also open a case/chat online on NETGEAR support to further assist you setting up this VLAN.

Regards,

[rand__]

Hi JohncarloV,

thanks for your answer.

I would think that I wouldnt need to define a gateway if all VLAN 6 members are on the same L2/Subnet? I've been assigning static IPs for this in the same /24 Class C subnet, so there should be no routing involved. Since this is a flat/single subnet there is no default gw to add in the first place (as none of the switches would qualify as router/have a routing interface).

Is that a misconception on my side?

Happy to try your setup o/c if you think this might resolve the issue, but would not really cover the final solution design I was looking for to be honest.

Thanks,

regards

[JohnC_V]

Hi rand__,

We cannot separate a single network address to VLANs. VLANs are created to have a group of logical networks so it should have its own IP address and default gateway. If they are going to be working on the same subnet/network, no need to create VLANs anymore as it will be working on default VLAN 1. VLANs should be created first in the firewall or to your DHCP server that will serve as the gateway as the functionality of the switch is just an additional port from the router.

e.g.
VLAN 1 - 192.168.1.x /24
VLAN 6 - 192.168.6.x /24

One network per VLAN ID.

Regards,

[rand__]

Hi,

the separation into VLANs additionally to subnets was to separate the actual networks physically to prevent broadcast/multicast messages from impacting the other services. Additionally I need those to separate two DHCP servers running in my network (one internal, one DMZ).

My Vlan1 currently spans a /22 net, my other VLANs are on 12 /24 nets for various activities

My primary DHCP (Sophos FW VM) resides on VLAN 1 running at the other switch I can't reach.

Is your idea now to add 12 additional interfaces (one for each vlan) to that vm so that each of them has a default GW it could get assigned?

Still don't understand why - what is the purpose of the default GW if all IPs are in the same vlan - I thought a trunked vlan kind of extendes the L2 network to the other switch so ll hosts are in the same domain ... might be wrong o/c but have not found a good explanation anywhere...

Thanks

[rand__]

Could of course also add a single interface being member of all secondary vlans and spanning all subnets ... might be simpler.

Still dont understand why this is necessary when communication works fine on the same switch and no routing/L3 should be involved.

[JohnC_V · Accepted solution]

@rand__,

That's correct. Functionality of VLANs is to separate the actual/physical networks. VLANs also have a default gateway even if it is set to static and even if they are working on the same subnet. You should have a default gateway(router) configured if not the traffic will not route across the network. Have you tried the setup that I suggested? That is also how VLAN works even if you use different switches. Every network has its own default gateway even if we are not talking about VLANs.

Regards,

[rand__]

Just fyi - still working on this, having some issues setting up the GWs and connecting to them

[JohnC_V]

@rand__,

Are you using a VLAN aware router on this setup? I believe most of our switches has a lifetime chat support. I may suggest you to open a chat/case online on NETGEAR support so that our support experts may assist you on setting up VLANs on your switch.

Regards,

[rand__]

So, finally got around adding a bunch of nics to my router playing a default gw and in fact this works.

Totally still don't understand why this is required, but I'll leave that be 🙂

Thanks