Quick tip: VLAN interface status

Vijay sent me this question a while ago:

I have configured a L3 VLAN interface on a Cisco 3750 switch and assigned an IP address to it. I haven't assigned any ports to this VLAN. Why am I not able to ping the IP address of the VLAN interface from the switch itself?

The VLAN interface (like any other interface) has layer-1 and layer-2 state.

The layer-1 state is displayed in the Status column of the show ip interface brief command, the layer-2 state in the Protocol column.

A VLAN interface is always up, but its line protocol state tracks the state of attached ports: if at least one port is operational, the line protocol of the VLAN interface is up, otherwise it’s down. With no ports assigned to a VLAN, the line protocol of the VLAN interface is down, its IP address is not in the IP routing table and thus you cannot ping it.

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18 comments:

  1. Invitado 15 July 2009 10:16
    Hello, if there is not any port assigned to the vlan and up, the interface is down, so the only way is to put a
    no keepalive in the interface vlan so it will remain up and also write ip routing to activate inter vlan routing.

    kind regards
  2. Paul 15 July 2009 10:19
    Agreed. The SVI interface (interface vlan x) is not always up. It's only up when the following are true.

    The vlan is created (show vlan brief)
    At least one port that is associated to that VLAN is up

    OR

    The no keepalive option is enabled.
  3. Ivan Pepelnjak 15 July 2009 10:24
    The "no keepalive" option does not work on my router (1800, 12.4(15)T). On which box did it work for you?
  4. Invitado 15 July 2009 10:40
    I tried on physical interfaces, I didn't on logical but I always thought that this works on int vlans...
  5. Christoph 15 July 2009 12:14
    Try "no autostate" instead, that should do it...
  6. that1guy 15 July 2009 12:25
    "With no ports assigned to a VLAN, the line protocol of the VLAN interface is down"

    Dont forget this also includes trunk ports. I see this from time to time.
  7. alvarezp 15 July 2009 19:30
    Thanks for the "no autostate" tip!
  8. Diosbejgli 15 July 2009 23:17
    you can enter into vlan configuration, by vlan <id> and issue the "state active" command, and your Vlan interface will be up/up.
  9. Ivan Pepelnjak 16 July 2009 07:48
    Does not work on my SOHO router (181x, 12.4(15)T). The autostate calculation AND the VLAN state must be active for the interface to be up/up.
  10. mzi 20 July 2009 13:10
    Understanding and Troubleshooting the Autostate Feature in Catalyst Switches

    http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a0080160b14.shtml
  11. Ivan Pepelnjak 20 July 2009 13:40
    Thanks for the link. See also the follow-up post:

    http://blog.ioshints.info/2009/07/followup-vlan-interface-status.html
  12. Guest 06 September 2009 13:19
    this helped me. thanks
  13. zdr 11 June 2010 11:38
    hello,

    maybe you can comment on the following case:

    I have a vlan subinterface that always remains up
    the client route attached to the subinterface will always be advertised by my IGP from this subinterface even when the remote CPE is down

    Is there anyway to get a vlan subinterface to go down if the mac adresse of the remote CPE disparrears?

    thanks
  14. Ivan Pepelnjak 15 June 2010 18:26
    You probably need reliable static routing, BFD for static routes or Ethernet OAM.
  15. Adam 06 November 2010 17:13
    Hi ,

    Got a question , Please help out

    Vlan 99 UP DOWN <-- --> Will this happen if one or a few ports is down in the in the vlan ? Or if all ports down ?
  16. Faisal 19 October 2011 12:17
    If Vlan is down ,how to troubleshoot
  17. Faisal 19 October 2011 12:20
    I have VLAN 80 and VLAN 85,Suppose Vlan 80 is down,how to troubleshoot them.
  18. Unknown 14 May 2012 16:31
    With an 87x (IOS 12.4T7 w/ IP Services), in a router-on-a-stick scenario where I only wanted the trunk port to be a member of the VLANs, I had to force the vlans to be created in the VLAN database by temporarily issuing "switchport access vlan x" on an L2 interface. Else they would not show up in "sh vlan-switch brief", and the vlanx interfaces would be up/down.
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