1

Hello,

Please excuse me if my terminology is incorrect, since I am still new to IT.

I currently have the following set-up:

A Layer 3 Switch(configured for routing), and 3 other switches.

The Layer 3 Switch connects to a another switch by 2 fiber connections

Layer 3 Switch |||||||||||||||||||||| Switch 1

1/1/3 = VLAN 2 ++++++++++ 1/1/3 = VLAN2

1/1/4 = VLAN 41 ++++++++++ 1/1/4 = VLAN 41

Everything connected to to SWITCH 1 has full network connectivity, the issue is connecting from SWITCH 1 to Switch 2

Switch 1 ||||||||||||||||||| Switch 2

1/1/1 = VLAN 2 +++++++++ 1/0/47 = VLAN2

1/1/4 = VLAN 41 +++++++++ 1/0/48 = VLAN 41

Switchport mode access

switchport access VLAN X

Are on each interface.

VLAN 41 on switch 2 does not have full network connectivity,

Any ideas and solutions?

8 Spice ups
2

First off, is there an error in what you say your ports are connected to? You say your Switch 1:Port 1/1/4 is connected to “Layer 3 Switch” in the first part, but then you say that same port is also connected to Switch 2? How is the same port connected to two different switches at the same time?

Also, not sure what you mean by “full network connectivity”? Do you mean devices on Switch2:VLAN 41 cannot reach VLAN2? Do you have Layer 3 VLAN interfaces for both VLANs setup on your Layer 3 switch?

You don’t mention trunk ports at all, so not sure if that means you’re not using them. Normally ports used to connect switch<–>switch are in trunk mode so you don’t need multiple connections between switches for each VLAN.

1 Spice up
3

Hi thanks for the reply,

to answer your first question, you are right and that was a mistake on my end. Switch 1: Port 1/1/2 <—> Switch 2 : Port 1/0/48

By “Full network connectivity”, VLAN 41 can not talk to VLAN 2. I would assume that there are Layer 3 VLAN interfaces on the Layer 3 switch since SWITCH 1, is able to have both VLANs 2 and 41 communicating.

They were not set-up as trunk ports.

Since my initial post, I have tried to set-up a trunk port on L3 Switch: Port 1/1/2 ↔ Switch 3: Port 1/0/47

The settings on both ends currently are:

switchport mode trunk

switchport trunk native vlan 1

switchport trunk allowed vlan 2,41

Only VLAN 2 traffic is able to access other VLAN 2 traffic, while VLAN 41 is still unable to do so.

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If you are confident that you have defined the VLANs on each switch and you have enabled VLAN routing on the L3 switch (assigned an IP address in each VLAN), you should focus on the port(s) being used to connect the switches. These ports need to carry traffic for both VLANs. You will also have to determine whether traffic on the uplink(s) needs to be tagged or untagged. Depending on the make and model of the switches, this can vary. And if you are using switches from different vendors the settings may seem to be counter intuitive or contradictory.

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The question is that “full network connectivity” is not supposed to happen on VLANs.

So your core switch is connected to 3 other switches (using VLAN 2 & 41). So if you connect a lappy to the core switch…what VLAN is that port using (it literally boils down to that) ?

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@itaintbroke ​ To my understanding a L3 switch can act as a router and allow multiple networks/VLANs to communicate with each other, correct? There are two VLAN interfaces set-up with the default gateway IP addresses. VLAN 2 hosts are able to ping to the Default Gateway of VLAN 41 placed on the L3 switch, but not the last known and only working host we had prior to replacing an actual router with the L3 switch. Either I am missing the whole concept entirely, or should there be some type of setting to help route the VLAN 41 traffic onto the VLAN 2 network? (VLAN2 is the network that has our servers and connects us to the ISP)

@adrianyong4136 I am not sure what a “lappy”, but if you mean laptop? I connect through a console cable and putty in? Really sorry if I don’t understand all the terminology, still trying to learn as much as possible. But the Core switch has 2 separate ports dedicated to run both a VLAN2/VLAN41 fiber to each switch, I would like to try to have a working trunk to have it free up interfaces on the switch though.

7

You are correct in that a L3 switch can perform VLAN routing. For that to work, you need to have a VLAN interface configured on the L3 switch for each VLAN that is to be routed (it sounds like you have this covered).

Have you tried adding the “all” option to your trunk config (switchport trunk allowed vlan all) ? If this resolves your issue then you know that tagging on your trunk(s) is probably your issue.

Adrian_ych also makes a couple of great points. Concerning the “full network connectivity” aspect. If that is your goal, you do not need VLANs. If you have members of both VLANs on multiple switches, then you need to take a look at the default/native/PVID VLAN on those ports.

Are you using ingress filtering on ports that participate in multiple VLANs?

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Hi everybody,

So I found the issue to be the DHCP, statically assigning IP addresses on VLAN 41 is able to talk to VLAN 2 hosts, so that should mean that routing between vlans are good to go. I really appreciate everyone’s help and suggestions, and thank you for taking the time to reply to me.