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Misunderstanding Layer-2??? Ping computer within Switch

rumak18
Level 1
Level 1

Hello,

i am not sure if i understand accesssing Layer-2 devices from devices correctly. 

I have a Cisco Switch (i guess it does not matter which one) .

There is an INT GI0/1 where i have a computer connected . This interface is configured as an access port with vlan 39.

There is also an INT Gi0/2 where i have another computer connected. This Interface is configured as a access port with wlan 100.

I also have a router (internet access) also configured via access port (VLAN 100) to the switch.

Now i'm trying to ping the device in vlan39 from the switch and also from the computer in vlan 100. But both pings fail. 

I would at least have expected the switch to ping the computer in vlan 39 as it is directly conned. Am i misunderstanding here something? 

Just for clarity, there is no other ip interface on the switch. 

2 Replies 2

Ramblin Tech
Spotlight
Spotlight

In order for you to ping the vlan-39 computer from the switch itself (I assume you are on the switch console or accessing remotely via telnet/ssh), the switch would need a layer-3 interface attached to vlan-39. Such an L3 construct, depending on the switch model, might be referred to as an svi, bdi, interface vlan39, etc. If you do not have such an L3 construct configured, then a ping will fail, as it will have no interface in the same broadcast domain as the vlan-39 computer. Same is true pinging from the vlan-100 computer to the vlan-39 computer: they are in different broadcast domains so ARP cannot resolve the MAC addresses for the IP addresses.

You are also going to run into an issue with the router being on an access port instead of a trunk, if you want it to route between vlans 39 and 100. It would be helpful if you could provide some IP addressing and mask lengths for this scenario, in order for the community to assist better.

Disclaimer: I am long in CSCO