This has exhausted every resource I've found and nothing explains why enabling any vLAN besides the management vLAN automatically shutdowns the management vLAN rendering their switch ports useless for IP traffic.
It's a portable CCNA lab and following the exercises in Cisco's Exploration 3 and 4… creating a new management vLAN or using the default mgmt vLAN1 still Administratively shutdowns the currently running vLAN after "no shut" a different vLAN.
Switches aren't constrained to just one running vLAN, but why is my config instantly shutting down the other singular operating vLAN the instant I "no shut" a different vLAN.
Appended an abridged running config and thoroughly exhausted the troubleshooting methods. More suggestions for additional troubleshooting are well meant…
I'm in need of some skilled peek of my flawed config instead of more suggestions cause I've exhaustively troublehshooted and switched cables to the infinite.
By now, I'm leaning towards some insidious Cisco limitation in a workgroup switch but the 2940 has seemingly executed every function w/o objection.
Thanks in advance
====RUNNING CONFIG (ABRIDGED FOR CLARITY)
spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
!
interface FastEthernet0/1
switchport access vlan 99
switchport mode dynamic auto
mdix auto
spanning-tree portfast
!
interface FastEthernet0/2
switchport access vlan 99
switchport mode dynamic auto
mdix auto
!
interface FastEthernet0/3
switchport access vlan 30
mdix auto
!
interface FastEthernet0/4
switchport access vlan 20
switchport trunk native vlan 20
switchport mode dynamic auto
mdix auto
===SNIP===
interface Vlan1
no ip address
no ip route-cache
shutdown
!
interface Vlan12
no ip address
no ip route-cache
!
interface Vlan20
ip address 172.16.20.20 255.255.255.0
no ip route-cache
shutdown
!
interface Vlan99
ip address 172.16.1.3 255.255.255.0
no ip route-cache
Enabling VLAN interface:
square(config-if-range)#inte vlan 99
square(config-if)#no shut
square(config-if)#
00:58:52: %LINK-3-UPDOWN: Interface Vlan99, changed state to up
00:58:52: %LINK-5-CHANGED: Interface Vlan20, changed state to administratively down
00:58:53: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan99, changed state to up
do sh vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/5, Fa0/6, Fa0/7, Fa0/8
Gi0/1
10 FacultyStaff active
20 Students active Fa0/4
30 Guest active Fa0/3
99 ManagementNative active Fa0/1, Fa0/2
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
Best Answer
What you are actually referring to is the Switch Virtual Interface (SVI) and this assigns a L3 interface to a VLAN.
VLANs are L2 and do not require an SVI to function. This switch can support up to 128 VLANs.
The 2940 is a L2 switch. The SVI is only for management, and the switch does not have any L3 routing capabilities. As such, it only supports one active SVI at any time, as does the 2950 platform it is based upon.
For a quick reference as to it's capabilities, you can check the datasheet on Cisco's website.