Ping between VLANS connected all ports to unmanaged swithch

[shservicesvivaldi]

I have CBS250 switch.

All 24 ports of the CBS250 connected to 24 ports of the unmanaged switch.

No host connected to the unmanaged switch ports, only the CBS250 port to port.

I have 2 VLANs each have IP and configure to one different port each.

The VLANS configured as layer 3.

I tried to ping from the GUI in advance from VLAN to VLAN. The ping is successful even when one of the ports in the unmanaged switch connected to one of these VLANs is defective.

How can I set the VLANs so the ping from VLAN to VLAN will detect that the port is defective without connecting hosts to the unmanaged switch?

[balaji.bandi]

Not sure i am able to get what the test about, if you ping from switch sure the VLAN Gateway Pings. ?

I am lost contact with old switches, do you able to get show run from the device and post here removing confidential information.

give example of Layer 3 vlan information from where to where you pinging ?

[Jens Albrecht]

Hello @shservicesvivaldi,

the rules for the Vlan interfaces which are also calles SVIs (Switch Virtual Interfaces) are pretty simple.

The IP interface of a Vlan is up if there is at least one active port on the CBS250 that has this vlan assigned to it. It does not matter whether this is an access port or a trunk port, the only condition is that the vlan is assigned to this port and the port is active, meaning up and running.

This means that if you have more than one port that is assigned to a vlan, then the IP interface for this vlan will only go down and become unreachable if all these ports go down.

You mentioned that you have 2 vlans. So if you have several hosts in each vlan, then you will always be able to ping the IP interface if a single port goes down.

This is just the general description of how these things work. If you can share more details about your setup with a diagramm we might be able to give a more specific reply.

HTH!

[shservicesvivaldi]

Hi,
The setup is quite simple.
The purpose is to test the ports of the unmanaged switch without any
host connected to it.
VLAN1 is the default port optical port28 connected to the PC.
Port1 is VLAN2 as access port and port2 is VLAN3. Each has an IP.
I want to ping from VLAN2 to VLAN3 and in case the port1 or port2 on the
unmanaged switch is defective, the ping will fail.
I have a switch with known defective port but when I ping that port as
in the setup picture, the ping does not fail.
I use the ping GUI in advance mode.

Thank you.

[Jens Albrecht · Accepted solution]

Hi,

based on your setup the ping to Vlan 3 will only fail if port2 on your CBS250 goes down.

So when you connect your CBS250 to a defective port on your unmanaged switch, you should check whether the port on your CBS250 goes up or not. Only if the port on the CBS250 remains down, your ping will fail so it depends on the kind of defect that your unmanaged switchport has.

If the port on the CBS250 goes up when connected to the defective port on your unmanaged switch, then ping will not fail and you cannot detect this via ping.

Of course, if there is any other port on your CBS250 in vlan3 which is up, then your ping will also not fail.

HTH!

[shservicesvivaldi]

Hi,

Since you clarify this issue, does it mean that even I send a telnet data between the 2 LANS through the unmanaged switch it will not detect internal fault between these VLAN ports on the unmanaged switch?Is there any other way to use the CBS250 for this test?

Thank you for your help.

[Jens Albrecht]

Well, as previously mentioned it all depends on whether the defect on the unmanaged switch will cause the port on the CBS250 to go down. If not, then I cannot think of a method how to detect this on the CBS250 as the vlan IP interface will remain up and reachable.

[Joseph W. Doherty]

You might find a defective port, on the unmanaged switch, by using a somewhat different testing methodology.

On the CBS, setup two ports, one per VLAN with a SVI.  Connect one of two ports to unmanaged port 1.  Other to second unmanaged port.  Ping between SVIs.  Move unmanaged port 2 connection to unmanaged port 3.  Repeat ping test.  Repeat moving port connection.  Also, before ping testing, you can check interface stats, i.e. link up, expected bandwidth and duplex settings, etc.