VLAN protocol down

[Mykematt]

Hi all,

On a multilayer switch, my VLANs are down. I have read other posts about what to do but I can't seem to figure it out. I have created VLANs for the interface VLANs but that didn't work. I have also reinstalled packet tracer as I read that cisco has some administrative issue with protocols on some switches—that didn't work either.

Interface.    IP add.               OK?      Method.         Status.        protocol 

Vlan10       192.168.10.4    YES       manual            up              down

Vlan20       192.168.20.4    YES       manual            up              down

Kindly assist.

[Reza Sharifi]

Hi,

Not familiar with PT, but usually for a vlan to come up, you need to connect an end device (laptop, desktop, printer, etc) to a port on that switch and vlan, or add the vlan to the uplink port which is usually a trunk port.

HTH

[MHM Cisco World]

allow this VLAN in any trunk and it will be UP/UP

[Martin L]

as mentioned above, this is normal behavior of IOS layer 2 for switches;  in order for vlan x SVI to be UP UP, you must have VLAN x in vlan database (added to run config), at least one of ports must be assign to that vlan x (access port) and port must be active (UP), or port is a trunk port and vlan x is allowed.  there is a command to switch this behavior off but it probably does  not work in PT since PT is just a simulator.

similar post https://community.cisco.com/t5/routing/l3-svi-and-l2-vlans/td-p/4650821

Regards, ML
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[paul driver · Accepted solution]

Hello

Conf t
int x/x
switchport mode trunk
no shut

or

 int x/x
switchport host
switchport mode access
switchport acces vlan 10 
no shut

 int x/x
switchport host
switchport mode access
switchport acces vlan 20 
no shut

[Mykematt]

Thank you, it worked. But can you please tell me what I'm doing wrong. These two typologies can't communicate. I can't ping the computers on one from the other. Thank you.

[Martin L]

you can not have network 192.168.10.0/24 on left of a router and same 192.168.10.0/24 on right side (router in the middle).  Routers and L3 switches do stop Broadcast traffic, aka separate B-cast domains. You need a NAT/PAT to translate IPs or special L2 tunnel (advanced level) set up.   Note: L3 switches do not support NAT/PAT but routers do.    This is the same as my home router translate my private 192.168.1.10 IP into public IP which is forwarded by my ISP to your ISP who then translate it back to your private 192.168.1.10 IP address.  Notice that both you and I may have the same private IP or within same range. However, communication must use Public IP on one side, which can be translated into private same IP behind the scene on the other side.

Regards, ML
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