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Beginner

VLAN 1 is the only VLAN and its disabled

I have a 3750G switch in my production network that only has VLAN 1 on it. All ports are in a default state and VLAN 1 is disabled. The switch is passing traffic but shouldn't having the default VLAN shut down cause the ports not to pass traffic? If I start to create VLANs will that cause the switch to stop passing traffic?

Everyone's tags (6)
4 REPLIES 4
Beginner

VLAN 1 is the only VLAN and its disabled

Hello,

There are many reasons for it.

Could you attach the configuration? After that maybe I can help to answer your questions.

Thanks

Ronaldo

Beginner

VLAN 1 is the only VLAN and its disabled

Here it is. Not much to it.

Thanks

version 12.2

no service pad

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

!

hostname SW0CN2

!

no logging console

enable secret

enable password

!

no aaa new-model

switch 1 provision ws-c3750g-48ts

switch 2 provision ws-c3750g-48ts

system mtu routing 1500

ip subnet-zero

!

!

!

!

no file verify auto

spanning-tree mode pvst

spanning-tree extend system-id

!

vlan internal allocation policy ascending

!

interface GigabitEthernet1/0/1

!

interface GigabitEthernet1/0/2

!

interface GigabitEthernet1/0/3

!

interface GigabitEthernet1/0/4

!

interface GigabitEthernet1/0/5

!

interface GigabitEthernet1/0/6

!

interface GigabitEthernet1/0/7

!

interface GigabitEthernet1/0/8

!

interface GigabitEthernet1/0/9

!

interface GigabitEthernet1/0/10

!

interface GigabitEthernet1/0/11

!

interface GigabitEthernet1/0/12

!

interface GigabitEthernet1/0/13

!

interface GigabitEthernet1/0/14

!

interface GigabitEthernet1/0/15

!

interface GigabitEthernet1/0/16

!

interface GigabitEthernet1/0/17

!

interface GigabitEthernet1/0/18

!

interface GigabitEthernet1/0/19

!

interface GigabitEthernet1/0/20

!

interface GigabitEthernet1/0/21

!

interface GigabitEthernet1/0/22

!

interface GigabitEthernet1/0/23

!

interface GigabitEthernet1/0/24

!

interface GigabitEthernet1/0/25

!

interface GigabitEthernet1/0/26

!

interface GigabitEthernet1/0/27

!

interface GigabitEthernet1/0/28

!

interface GigabitEthernet1/0/29

!

interface GigabitEthernet1/0/30

!

interface GigabitEthernet1/0/31

!

interface GigabitEthernet1/0/32

!

interface GigabitEthernet1/0/33

!

interface GigabitEthernet1/0/34

!

interface GigabitEthernet1/0/35

!

interface GigabitEthernet1/0/36

!

interface GigabitEthernet1/0/37

!

interface GigabitEthernet1/0/38

!

interface GigabitEthernet1/0/39

!

interface GigabitEthernet1/0/40

!

interface GigabitEthernet1/0/41

!

interface GigabitEthernet1/0/42

!

interface GigabitEthernet1/0/43

!

interface GigabitEthernet1/0/44

!

interface GigabitEthernet1/0/45

!

interface GigabitEthernet1/0/46

!

interface GigabitEthernet1/0/47

!

interface GigabitEthernet1/0/48

!

interface GigabitEthernet1/0/49

duplex full

!

interface GigabitEthernet1/0/50

!

interface GigabitEthernet1/0/51

!

interface GigabitEthernet1/0/52

!

interface GigabitEthernet2/0/1

!

interface GigabitEthernet2/0/2

!

interface GigabitEthernet2/0/3

!

interface GigabitEthernet2/0/4

!

interface GigabitEthernet2/0/5

!

interface GigabitEthernet2/0/6

!

interface GigabitEthernet2/0/7

!

interface GigabitEthernet2/0/8

!

interface GigabitEthernet2/0/9

!

interface GigabitEthernet2/0/10

!

interface GigabitEthernet2/0/11

!

interface GigabitEthernet2/0/12

!

interface GigabitEthernet2/0/13

!

interface GigabitEthernet2/0/14

!

interface GigabitEthernet2/0/15

!

interface GigabitEthernet2/0/16

!

interface GigabitEthernet2/0/17

!

interface GigabitEthernet2/0/18

!

interface GigabitEthernet2/0/19

!

interface GigabitEthernet2/0/20

!

interface GigabitEthernet2/0/21

!

interface GigabitEthernet2/0/22

!

interface GigabitEthernet2/0/23

!

interface GigabitEthernet2/0/24

!

interface GigabitEthernet2/0/25

!

interface GigabitEthernet2/0/26

!

interface GigabitEthernet2/0/27

!

interface GigabitEthernet2/0/28

!

interface GigabitEthernet2/0/29

!

interface GigabitEthernet2/0/30

!

interface GigabitEthernet2/0/31

!

interface GigabitEthernet2/0/32

!

interface GigabitEthernet2/0/33

!

interface GigabitEthernet2/0/34

!

interface GigabitEthernet2/0/35

!

interface GigabitEthernet2/0/36

!

interface GigabitEthernet2/0/37

!

interface GigabitEthernet2/0/38

!

interface GigabitEthernet2/0/39

!

interface GigabitEthernet2/0/40

!

interface GigabitEthernet2/0/41

!

interface GigabitEthernet2/0/42

!

interface GigabitEthernet2/0/43

!

interface GigabitEthernet2/0/44

!

interface GigabitEthernet2/0/45

!

interface GigabitEthernet2/0/46

!

interface GigabitEthernet2/0/47

!

interface GigabitEthernet2/0/48

!

interface GigabitEthernet2/0/49

duplex full

!

interface GigabitEthernet2/0/50

!

interface GigabitEthernet2/0/51

!

interface GigabitEthernet2/0/52

!

interface Vlan1

no ip address

shutdown

!

ip classless

ip http server

!

!

control-plane

!

!

line con 0

exec-timeout 0 0

line vty 0 4

password

login

line vty 5 15

password

login

!

end

Participant

Re:VLAN 1 is the only VLAN and its disabled

I see that the VLAN 1 SVI (interface vlan 1) had no address assigned and is shut down, but I don't believe IOS wink allow you to remove VLAN 1 (no vlan 1 from global config).

The SVI only provides a layer 3 interface on the vlan (logical), but shutting down the SVI won't stop forwarding of traffic on the vlan.

Sent from Cisco Technical Support Android App

Hall of Fame Guru

Re: VLAN 1 is the only VLAN and its disabled

As stated by Edwin you cannot disable vlan 1.  All your ports are still in vlan 1 and so any devices connected to ports on that switch are in the same vlan. The L3 SVI doesn't have an IP so you won't be able to route to any other vlans but you don't have any other vlans on the switch.

If you add more vlans it will not affect the forwarding of existing traffic. If you wanted to add more vlans then you would need to -

1) create the vlans at L2

2) create a L3 SVI for each vlan and assign an IP from the vlan subnet. Note each vlan will have a different subnet *** this is assuming you want the 3750 to route between the vlans.

3) if you want the vlan 1 devices to be able to communicate with the new vlans you will need to give an IP from the vlan 1 subnet to the vlan 1 SVI ie. the interface vlan 1 bit in your config

4) you then need to assign the port(s) into the vlans you want. Until you do this no forwarding of existing traffic will be affected.

If you assign a device into one of your new vlans but do not do step 3) first then the device in the new vlan will not be able to communcate with the vlan 1 devices.

You should also note that the L3 SVI will not come up unless -

i) you have a port that is up/up in that vlan 

or

ii) you have a trunk connection on the switch to another switch for example which allows that vlan

So if you do step 2) the SVI's won't come up until you assign a port to that vlan.

Finally if you do want to route you may need to enable ip routing on the switch (can't remember whether it is enabled by default).

Jon

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