vlan interface down

Unanswered Question

How do figure out why? I tryed no shut down, still down...

41-Switch-1#sh int vlan 3

Vlan3 is down, line protocol is down

Hardware is EtherSVI, address is 000a.f421.e800 (bia 000a.f421.e800)

Internet address is

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts (0 IP multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 packets output, 0 bytes, 0 underruns

0 output errors, 1 interface resets

0 output buffer failures, 0 output buffers swapped out

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Overall Rating: 5 (4 ratings)
massimiliano.se... Wed, 04/09/2008 - 07:23


Do you have ports in VLAN 3? Try to put one port in VLAN 3..

I hope this helps.

Best regards.


mohammedmahmoud Wed, 04/09/2008 - 07:35


There needs to be atleast 1 up/up interface within the VLAN for the VLAN SVI interface to be in an up/up state - one port in the VLAN should be in the connected state or there should be a running trunk to another switch - if the SVI interface is created but the VLAN is not configured on the switch the SVI interface will be down/down (which is your case), if the VLAN is created on the switch but no port assigned to this VLAN is UP/UP the SVI becomes up/down.


Mohammed Mahmoud.

Richard Burts Wed, 04/09/2008 - 08:13


The suggestions about needing to have at least 1 active port (or inclusion in an active trunk) is a good point. Another question is whether this switch is a layer 2 switch or layer 3 switch. Layer 3 switches can have multiple VLAN interfaces that are active. A layer 2 switch can have multiple VLANs but can have only 1 VLAN interface that is active. If this is a layer 2 switch and if there is another VLAN interface would be a reason why this VLAN interface is down.



mohammedmahmoud Wed, 04/09/2008 - 08:26

Hi Rick,

I believe that layer 2 switches will have only one UP/UP SVI for management, while any other created SVI will be in the administratively down status (at least this was the case with my 2900XL), but since this SVI is down/down then i believe that as i've suggested the VLAN is not configured on the switch.

[edit] Another thing, from the output, "Hardware is EtherSVI", this is only the case with L3 switches, if it was L2 i believe it should be "Hardware is CPU Interface".


Mohammed Mahmoud.

mahesh18 Fri, 05/16/2008 - 13:26

Hi Mohammed

what is SVI interface in vlan.my understanding is that when we make the vlan

aqnd assign it physical interfaces then that

vlan is SVI?

if not please explain me what is SVI?and when

and why do we need it?

also how is it different form VLAN?

Jon Marshall Fri, 05/16/2008 - 14:05


SVI = Switched Virtual Interface.

When you create a vlan ie.

3550(config)# vlan 10

3550(config-vlan)# name v10

this vlan is a L2 vlan. If you allocate ports into this vlan then any devices attached to this port can communicate with each other.

But if you had another vlan eg. vlan 11 and you wanted your devices in vlan 10 to be able to communicate with devices in vlan 11 you need to create SVI's for each vlan. These SVI are L3 interfaces for the vlans and they allow inter-vlan routing. An SVI is created by

3550(config)# int vlan 10

3550(config-if)# ip address

and then set the default-gateway on each device in vlan 10 to be


mahesh18 Fri, 05/16/2008 - 14:13

Hi Jon,

thanks for reply

so these SVI can we create these on layer

2 switches by assigning them IP address or

they have to be in layer 3 device like Router

or Layer 3 switch?

Jon Marshall Fri, 05/16/2008 - 14:17


On a layer 2 switch you can have one SVI only and this SVI is used for remotely accessing the switch to manage it. You would not use the IP address of this SVI as a default-gateway for clients.

On a layer 3 switch you can have multiple SVI's and the L3 switch will route between these vlans.


mahesh18 Sun, 05/18/2008 - 12:51

Hi Jon,

i was reading book of Oreilly,

It says that switch 6509 in hybrid mode.

2 vlans have been created on 6509

catos-6509> sh vlan shows

vlan name

1 default active status

10 lab vlan active status

20 vlan0020 active status

now i go to mfsfc mode

and config the SVI by

MSFC--6509# config t

MSFC--6509# int vlan 20

MSFC--6509# ip address

MSFC--6509# no shutdown

now i run this command

MSFC--6509# sh ip int brief

Vlan 20 down down

it says tin book that SVI will now come up

unless there is active por ton layer 2.

in book they have assign IP address to the

CatOS Management int SCO, and place i tin vlan 20.

CatOS-6509 set int sco 20

Can u please expalin me last part Catos ?Management inetrface SCO??????????????

i do not get that part

Richard Burts Sun, 05/18/2008 - 17:52


In the Catos based switches the syntax does not support configuring interface vlan x as the management interface of the switch (that is more a mechanism of the IOS based switches). In the Catos based switches sc0 is the management interface for the layer 2 switch.



mahesh18 Mon, 05/19/2008 - 06:04

Hi rick

thanks for reply

can u explain me in more detail please

Richard Burts Mon, 05/19/2008 - 09:16


A layer 2 switch will have a single virtual interface which is used to manage the switch. How the management interface is identified (and how it is configured) depend on the type of switch and what type of operating system it uses. In the example that you posted the switch is a 6500 switch and is running CatOS operating system. In these switches the management interface is called sc0.

In other switches (such as the 3550 in the example from Jon) the management interface is called interface vlan x

So sc0 is the management interface for a CatOS type of switch and interface vlan x is the management interface for an IOS type of switch.



mahesh18 Mon, 05/19/2008 - 10:11

Hi Rick,

thanks for reply

so we make SVI for vlan in MSFC side and assign it IP address and in order that vlan

should be UP UP we need to assign IP to Sc0 interface in MSFC and these two ips have to be different right one assigned to SVI and other assign to Sc0????


Jon Marshall Mon, 05/19/2008 - 10:23


The sc0 interface has nothing to do with the MSFC. The MSFC on a 6500 is for routing and here is where you would create your L3 SVI's.

As Rick has stated sc0 is for managing a CatOS switch. It may help to clear up the difference between native and hybrid on a 6500.

Native mode means that the L2 switch and the L3 part (MSFC) are configured using just IOS. So if you wanted to assign a management interface to a 6500 in native mode you would use an SVI an assign it an address.

Hybrid mode means the L2 switch is running CatOS and the L3 part (MSFC) is running IOS. So if you wanted to assign a management interface to a 6500 in hybrid you use the sc0 interface in the CatOS configuration and assign an IP address to that.

Does this make sense ?


mahesh18 Mon, 05/19/2008 - 10:32

Thanks for helping actually i was reading this part from book

There are no SVIs active on the MSFC-not even VLAN 1. Let's add an SVI for VLAN 20 and see what happens:

Code View: Scroll / Show All

MSFC-6509# conf t

Enter configuration commands, one per line. End with CNTL/Z.

MSFC-6509(config)# int vlan 20

MSFC-6509(config-if)# ip address

MSFC-6509(config-if)# no shut

MSFC-6509(config-if)# ^Z


17w2d: %LINK-3-UPDOWN: Interface Vlan20, changed state to down

17w2d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan20, changed state to down


MSFC-6509# sho ip int brief

Interface IP-Address OK? Method Status Protocol

Vlan20 YES manual down down

The SVI is now there, but it won't come up. The SVI will not come up unless there is an active port in the VLAN in layer two. I often forget this fact and, after adding the SVIs, go off to create my VLANs only to find that none of them will come up. To illustrate the point, I'll assign an IP address to the CatOS management interface SC0, and place it in VLAN 20. This will put an active device in the VLAN:

CatOS-6509: (enable) set int sc0 20

Interface sc0 vlan set, IP address and netmask set.

Now, with something active in VLAN 20, the VLAN 20 SVI comes up in the MSFC:

Code View: Scroll / Show All

MSFC-6509# sho ip int brief

Interface IP-Address OK? Method Status Protocol

Vlan20 YES manual up up

Now i know that Sc0 management IP of Cat OS is assigned at switching side.and we can assign only 1 ip at switching side which is using CatOS right?

Jon Marshall Mon, 05/19/2008 - 10:37

"Now i know that Sc0 management IP of Cat OS is assigned at switching side.and we can assign only 1 ip at switching side which is using CatOS right?"


The other way to ensure that your vlan interfaces come up is if you have a L2 trunk to another switch and the vlan is allowed on this trunk. Then the interface would come up as well.


mahesh18 Tue, 05/20/2008 - 09:21

hi jon,

i have switch 6509 which on cat os side has

number of vlans with ip addresses???????????

so on cat os side is it ok to have no of vlans with ip addresses

Richard Burts Tue, 05/20/2008 - 09:34


If it is truly a Catalyst 6509 and running CatOS on the switch side, then I do not believe that you can put multiple IP addresses on multiple VLANs. Perhaps you can post some details from the switch so that we can see what you are talking about.

The only way that I know to put multiple IP addresses on multiple VLANs is either to be on the MSFC rather than the switch or to be running IOS code rather than CatOS.



mahesh18 Tue, 05/20/2008 - 11:50

thanks rick for reply

actually those ips were vlan names

i am ok

thanks once again


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