Communication between different Systems / VLANS

[MMSAG_Elias]

Hello, 

I'am employed at a AV Installation Company and for one customer we have installed a Audio- Video & Lighting System. Therefore we needed a network and we have installed several Cisco SG350 switches, which were connected to the circuit via optical fiber. 

A few weeks ago we added a new SG350-52MP (firmware 2.5.7.85) to our system. 

The existing system has the IP range 10.70.160.0 /24. / Main Switch IP Adress: 10.70.160.2 (VLAN A) 

The new Switch has the IP range 10.70.161.0/24 / Switch IP Adress: 10.70.161.10 (VLAN B)

Now we need to connect the networks with each other. There for we connected them via optical fiber. 

From VLAN A I can ping VLAN B with an IP Adress 10.70.161.0/24. The other way around as well.

But we need to allow a communication between specific devices which are in different VLANS.

As you now can imagine, we are not really firm with configuring those Switches. 

Can you explain me an exact way to allow communication between those VLANS? I watched several Videos and Tutorials on Youtube, but nothing was working for me.. 

Thanks in advance for your help.

[Giuseppe Larosa]

Hello @MMSAG_Elias ,

if one device has SVI that is L3 interface VLAN in both VLANs it can act as the inter VLAN multi layer switch.

This is what you need to do define VLAN B on main switch. Assign an IP address in new subnet to it and have all systems using it as default gateway in VLAN B

Edit:

the link between main switch and new switch must be an 802.1A trunk allowing both VLAN A and VLAN B on both sides.

Hope to help

Giuseppe

[MMSAG_Elias]

Hey Giuseppe, 

thank you. 

I have added two VLANS on the added Switch, assigned the SFP Port to the VLAN A and set an IP Adress for this VLAN. From VLAN A I can ping the assigned IP Adress. 

I also changed the Default Gateway to this IP Adress, but this wasn't working for me. 

Both ports are assigned to Trunk ports. 

[balaji.bandi]

But we need to allow a communication between specific devices which are in different VLANS.

what is that VLANS ? you can do same way you did other VLAN ? like you did "From VLAN A I can ping VLAN B with an IP Adress 10.70.161.0/24. The other way around as well."

what is not working ?

[MMSAG_Elias]

Sorry, I have expressed myself badly. 

When i am connected to the new Switch with an IP Adress 10.70.160.0, I can ping for example the 10.70.160.2. 

But when i am connected to the new Switch with an IP Adress 10.70.161.0 I can't ping 10.60.160.2

So for me the routing between those VLANs doesn't work, or am I mistaken?

[balaji.bandi]

When you connecte these 2 device, have you passsed the VLAN in trunk, do you have routing between these device communications ?

If your main switch handling VLAN X and VLAN Y, (and SVI configured oh switch (layer 3 mode), then IP routing works as expected.

If the VLAN Layer 3 interface only available each switch, that required extend your VLAN and SVI to other switch.

Option 1

One of the switch act as Layer 3 device, other just act as Layer 2 only

Option 2

create  both VLAN SVI on each switch (if you looking this setup) or option 1 is good option.

SWITCH 1 ( VLAN X  and VLANY  ----(Trunk) SWITCH 2 ( just Layer 2)

https://www.youtube.com/watch?v=NLMKwYSlQDY

[Richard Burts]

There are several things about this that I am not clear about:

- the original post says "But we need to allow a communication between specific devices which are in different VLANS." Does this mean that only certain devices in vlan B should communicate with certain devices in vlan A? Or does it mean that any device in vlan B should communicate with any device in vlan A? 

- the original post says "There for we connected them via optical fiber." Can you tell us how the port for the connection on the first switch is configured? Can you tell us how the port for the connection on the second switch is configured?

- can you tell us whether IP routing is enabled on one or both switches?

[MMSAG_Elias]

Hey Rick, thank your!

- We only need certain devices to communicate, but I think its easier to allow communication for all devices. 

- Both ports are configured as trunk ports

- On the existing Switch we haven't changed anythink. So there is only one VLAN (Also no IP Routing enabled)

On the added Switch we have set up two VLANs with two IP Adress and IP routing is enabled. 

[Giuseppe Larosa · Accepted solution]

Hello @MMSAG_Elias ,

>>

On the existing Switch we haven't changed anythink. So there is only one VLAN (Also no IP Routing enabled)

On the added Switch we have set up two VLANs with two IP Adress and IP routing is enabled.

OK then on the existing switch the ip default-gateway has to be the IP address of the new switch on VLAN A

ip default-gateway <ip-address>

You can set this on the GUI  of the switch.

The new switch is in charge of inter VLAN routing

The trunk link carrying both VLAN A and VLAN B is needed if there are hosts in both VLANs on both switches.

Hosts in both VLANs A and B need to use new switch IP address in respective subnet as default-gateway

Hope to help

Giuseppe