Inter-VLAN Routing w/ 3750 Switch

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Apr 11th, 2008
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I am having an issue with routing on my 3750 switch. I turned on routing with the "ip routing" command and confirmed it was enable by doing a "show run" command. I then created several VLAN's and assigned each of them an IP address and subnet mask. I then assigned the appropriate interfaces to the desired vlans. I did put in the "show vlan brief" command to confirm that the interfaces were in the correct VLAN's. At this point, I took a few workstations and assigned them a static IP in the same subnet as the VLANs they were attached too but I was unable to ping anything. When I ran the "show ip interface brief" command I saw all but one vlan read status up but protocol down. I am stumped and to why this occurred. I am hoping this is something simple that I overlooked. Any assistance or suggestions would be very appreciated.


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Overall Rating: 4 (1 ratings)
Jon Marshall Fri, 04/11/2008 - 06:28
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Can you post the switch config

lamav Fri, 04/11/2008 - 07:15
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Without seeing the config, I have a hunch you forgot to create the vlans in L2..

vlan 2

name test_vlan

vlan 3

name server_vlan


As I said, just a hunch :-)

Sup, Jon?? Long time....

Craig Norborg Fri, 04/11/2008 - 11:51
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That would be my guess too. When your working with a Layer-3 switch, you must configure both the Layer-2 VLAN as shown in lamav's post, ie:

vlan 2

vlan 3

as well as the Layer-3 side of the VLAN, which you do with the interface command:

interface vlan 2

ip address X.X.X.X

interface vlan 3

ip address X.X.X.X

Otherwise your Layer-3 interfaces don't come up. They also won't come up if there isn't an interface up on that VLAN too, another common mistake, but it doesn't sound like the case this time.

Rick Morris Fri, 04/11/2008 - 07:24
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If you only ever show one vlan then you do not have layer 3 running on the switch. In layer 2 you will only have 1 native vlan. If you continue to change VLAN's then the last VLAN you created will be the VLAN shown.

ionutionescu Sat, 04/12/2008 - 07:18
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Usually, you have line up and protocol down on a SVI (vlan interface) if there is no active (line up and protocol up) port assigned to that specific vlan.

Try to shut / no shut the SVI and make sure to check the port vlan assignment.

Also be sure to check that each SVI has an IP address as posted above.

Hope it helps.


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