08-03-2006 07:56 AM - edited 03-03-2019 04:20 AM
Is there a method that enables you to keep a vlan "UP", even when none of the physical interfaces assigned to that vlan are connected?
08-03-2006 07:57 AM
you can use a trunk that supports the VLAN and that should keep it up. (if you can use a trunk)
unless there is at least 1 active port in VLAN, it will stay down.
08-03-2006 08:24 AM
Actually, I'm trying to keep VLAN1 (native vlan) up. I do have several interfaces, that are trunking, assigned to this vlan. Unless these interfaces are physically connected, VLAN1 stays "DOWN". The switch in question has a WAN connection through an interface in a different VLAN. This interface is up, but I cannot TELNET into the switch because VLAN1 is down.
08-03-2006 10:30 AM
If you are using vtp, you can "force" the VLAN active using those commands; depending on the switch you are using, this is done a number of different ways.
newer IOS switch running native mode -
conf t
vlan 1
state active
exit
wr mem
older IOS switch
From an enable prompt -
vlan database
[enters vlan database mode)
[Note: Newer IOS warns that this is deprecated and will not show help -- the help is as follows -
switchname#vlan database
% Warning: It is recommended to configure VLAN from config mode,
as VLAN database mode is being deprecated. Please consult user
documentation for configuring VTP/VLAN in config mode.
switchname(vlan)#?
VLAN database editing buffer manipulation commands:
abort Exit mode without applying the changes
apply Apply current changes and bump revision number
exit Apply changes, bump revision number, and exit mode
no Negate a command or set its defaults
reset Abandon current changes and reread current database
show Show database information
vlan Add, delete, or modify values associated with a single VLAN
vtp Perform VTP administrative functions.
switchname(vlan)#vlan ?
<1-1005> ISL VLAN index
switchname(vlan)#vlan 1 ?
are Maximum number of All Route Explorer hops for this VLAN
backupcrf Backup CRF mode of the VLAN
bridge Bridging characteristics of the VLAN
media Media type of the VLAN
mtu VLAN Maximum Transmission Unit
name Ascii name of the VLAN
parent ID number of the Parent VLAN of FDDI or Token Ring type VLANs
ring Ring number of FDDI or Token Ring type VLANs
said IEEE 802.10 SAID
state Operational state of the VLAN
ste Maximum number of Spanning Tree Explorer hops for this VLAN
stp Spanning tree characteristics of the VLAN
tb-vlan1 ID number of the first translational VLAN for this VLAN (or zero
if none)
tb-vlan2 ID number of the second translational VLAN for this VLAN (or zero
if none)
switchname(vlan)#vlan 1 state ?
active VLAN Active State
suspend VLAN Suspended State
switchname(vlan)#vlan 1 state active (enter)
This will make the VLAN active.
Note that it "works" even when there is no help.
There's a way to do it for CAT OS, but I only have VTP clients on my few remaining Cat OS switches.
Good luck -
Nick
(PS - if this helps, please 'rate' the answer ! :-) )
08-04-2006 08:18 AM
Hello Nick,
The native vlan, in my case VLAN1, is active by default. And even though a vlan is active, it doesn't mean that the VLAN is "UP" and the protocol is "UP". At this point it still seems that you have to have something physically plugged into an interface that is in said vlan. I think the solution to my problem is to create a loopback interface. They are always "UP" and I should be able to telnet into the switch even though the native vlan is "DOWN". Thanks for your response and input.
08-04-2006 08:31 AM
The interface vlan x (no matter if it's vlan 1 or 2 or 3) is a logical interface. It will NOT remain up unless the physical port is "connnected". the physical port can be access port belonging to vlan x or a turnk port where vlan x is part of the vlans forwarding. There is not way to keep the logical interface up if there are no connected physical port that belongs to this vlan.
08-04-2006 11:08 AM
Thank you for the clarification. It looks like I was trying to do something that's not possible. I think I found the solution though. I created a loopback interface. Even though this is a virtual interface, like a vlan, the loopback is always up and I can now telnet to my switch. Thanks for the response.
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