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Cisco Catalyst switch - Keep VLAN UP

Posted on 2014-11-20
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Last Modified: 2014-11-30
I have a Cisco 3750X switch. I am configuring layer 3 SVIs and I do not have access to the device to physically connect devices. I want to put the devices in UP/UP state. I beleive there's a way to do this with VLAN State active or some other command. Does anyone know the configuration needed so I can fully configure and test ping on SVIs?
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Question by:jbla9028
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by:Predrag Jovic
ID: 40455291
This should work.
Add interface to your VLANs and under interface issue no keepalive. Port should come up, so VLAN too.
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by:Jan Springer
ID: 40455350
have you tried putting the one of the physical interfaces of that vlan into loopback mode?
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by:jbla9028
ID: 40455666
I have not. how do I do that?
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by:Jan Springer
ID: 40455684
take an rj45 loop connector and plug it into the interface.

the pinouts should be 1 to 3 and 2 to 6.
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by:jbla9028
ID: 40455701
Jan, thank you but I do not have physical access to the device for a few weeks. I thought there was another way that could be done via CLI to set the SVI into UP/UP.  on a router its called no autostate. That command however is only available on Cisco routers.



http://packetlife.net/blog/2009/nov/9/svi-autostate/
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by:Jan Springer
ID: 40455708
some router interfaces can be soft forced into loopback but i don't see where the 3750 interfaces can do this.
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by:Predrag Jovic
ID: 40455844
Did you tried to add VLAN to trunk (and check is really VLAN created, just in case, I know it should, but...)?
switchport trunk allowed vlan add xx

If SVI exist on switch, you should add 1 port to forwarding state and adding VLAN to trunk could do that.
I just checked, it worked in GNS3, but on a real switch, who knows. :)
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by:Jan Springer
ID: 40455856
at least one physical interface passing that vlan has to be up/up before the vlan can come up/up.
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by:Predrag Jovic
ID: 40455876
Is there anything connected to switch? Or there's no nothing at all attached to switch, not on a single port?
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by:Jan Springer
ID: 40455881
you can't have just any port.  the switch has to have a vlan connected port in up/up or that vlan being passed and recognized across a trunked interface for the vlan interface to be up/up.
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by:Predrag Jovic
ID: 40455905
Yes that's right (I forget that I have already did something on config - my suggestion don't work), but how author is connected to switch? Out of band?
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by:Jan Springer
ID: 40455909
yes and a software loop doesn't appear to be an option.
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by:jbla9028
ID: 40455914
I am currently connected to the switch via the console port. No cables are connected to interfaces. It not a critical issue so I will be able to eventually hook up the interface and set interface to trunk all traffic to test. I just figured there had to be some way. It looks like on 4500 switches it works.
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Jan Springer earned 167 total points
ID: 40455920
my misunderstanding.  i thought you wouldn't have physical access for a few weeks.  this is a good opportunity to create a loopback rj45 connector.
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by:Craig Beck
Craig Beck earned 166 total points
ID: 40456510
I don't think you can do this on a switch.  For a SVI to be UP/UP at least one port must be in the STP forwarding state.  If you issue the no keepalive command on a port it will itself be UP/UP, but STP will not be forwarding on that port, so the SVI will stay UP/DOWN.  You don't need a port to be in a trunk though - it can be an access port.

Why, if you don't have any devices connected to the VLAN, do you want the SVI to be UP anyway?
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by:aleghart
aleghart earned 167 total points
ID: 40456542
IIRC, if the SVI is down, then you can't use that IP address for telnet/ssh/http access to the switch.

Is this 3750 trunked to another switch?  Put the same VLAN on another switch and the trunk.  Give the second switch an IP address on that VLAN.

That should get the two switches talking to each other, wouldn't it?
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by:Craig Beck
ID: 40456833
@aleghart - that's correct, although the switch is already reachable remotely via IP so I don't imagine the requirement is simply to telnet/SSH to the switch using a different IP.
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by:aleghart
ID: 40457034
Sometimes, you remove the IP that's in the user LAN, and use only a management VLAN for access.  Makes it easy to limit access to the management interfaces, and helps lock down in a WAN environment where many subnets are routed to other sites.

Site A user LAN subnet can see Site B's user LAN subnet, but not the management subnet.
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by:Craig Beck
ID: 40457155
I know that, but access to switch via WAN is up obviously so no management access via user LAN is in effect at the moment.
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Author Closing Comment

by:jbla9028
ID: 40472828
unfortunately none of these worked. I ended up getting interfaces setup and the IPs came up. Thank you for the help though.
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by:Craig Beck
ID: 40472829
You should ask for the question to be deleted then, instead of picking an incorrect answer.
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