L3 SVI and L2 VLANS

[abc1235]

Hallo,

This is a rather basic question but I will ask it anyway I copied the working running configs from a faulty 891 Cisco router to another one. Initially, it didn't work (clients were not getting an IP even though the VLAN was pingable) and on troubleshooting, I saw that the L3 SVIs were configured but the VLANs weren't. I configured the L2 VLANs but on checking the running configs, they were not there. I went ahead to make more changes on trial basis and finally the clients got an IP address. I am convinced that it was after the creation of the L2 VLANs would have fixed the problem, but I would like a confirmation of the same. Is that the case? Must L2 VLANs be created first before the SVIs?

Thanks.

[frknl]

Running-config

doesn't cover vlan database, so without

interface vlan x

ip add x.x.x.x/prefix-length

command it will not work.

[MHM Cisco World]

for the SW you can start with L3 SVI or L2 VLAN, AND for router I think it same you can config the SVI then this SVI is down until you add L2 VLAN to router which turn UP.

[Martin L · Accepted solution]

Yes, You Must have L2 VLANs in database before the SVIs?  Or SVI vlan x will stay down until you add vlan x.  Also, there must be an active port in vlan x for SVI x to be up up. you can change this default behavior with

no switchport autostate

or

switchport autostate exclude

command. This port can be access port or a trunk but for sure vlan x must exist in vlan database (stored in flash of a device). 

Regards, ML
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[abc1235]

Thank you all for the responses. I now understand where the problem was

[paul driver]

Hello
L3 switch in particular , you need to create the L2 vlan as its not created as/when you create its L3 svi equivalent