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Layer 2 Network - Access port and ping device - do i misunderstand?

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) . See attached file.

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. 

1 Accepted Solution

Accepted Solutions

Joseph W. Doherty
Hall of Fame
Hall of Fame

"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?"

Yes, you misunderstand that your switch's IP, and the router and right side computer are all in VLAN 100, network 10.1.0.0/24 which has no L2 or L3 path to your left side computer in VLAN 39, network 10.2.39.0/23.  I.e. just having the switch and the left most computer physically connected, doesn't necessarily mean they are logically connected.  Logically, due to their VLANs, the two VLANs (39 and 100) are "invisible" to each other.

What VLANs accomplish, on one physical switch, is multiple logical switches.  I.e. it's like you have a physical switch for VLAN 39 and one for VLAN 100, and they are not connected to each other, although the VLAN 39 logical switch has one logical connection, the left side computer while the VLAN 100 logical switch has two logical connections, the right most computer and router.

View solution in original post

2 Replies 2

Martin L
VIP
VIP

To ping PCx in vlan X from PCB in vlan B u need routing; like L3 switch with SVIs or Router -so called router-on-a-stick, aka ROAS. search the Net for ROAS.  Using vlans on any switch is to limited Broadcast , B-cast, domains so that u have less traffic inside a vlan, u also have more control over who can reach whom. 

Tp ping a L2 switch locally (or L3 switch SVI) such switch needs to have Switched Virtual Interface, aka SVI,  with IP and UP UP state (also vlan x present in database). Also, L2 switch will need ip default-gateway command with IP in order to be able reach remote networks.

Regards, ML
**Please Rate All Helpful Responses **

 

Joseph W. Doherty
Hall of Fame
Hall of Fame

"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?"

Yes, you misunderstand that your switch's IP, and the router and right side computer are all in VLAN 100, network 10.1.0.0/24 which has no L2 or L3 path to your left side computer in VLAN 39, network 10.2.39.0/23.  I.e. just having the switch and the left most computer physically connected, doesn't necessarily mean they are logically connected.  Logically, due to their VLANs, the two VLANs (39 and 100) are "invisible" to each other.

What VLANs accomplish, on one physical switch, is multiple logical switches.  I.e. it's like you have a physical switch for VLAN 39 and one for VLAN 100, and they are not connected to each other, although the VLAN 39 logical switch has one logical connection, the left side computer while the VLAN 100 logical switch has two logical connections, the right most computer and router.