SVI issue !!

Unanswered Question
Oct 14th, 2008

today i had a strnage issue with SVI in cat 3570

i created the L2 vlan then i created the SVI for that vlan i put no shut

but the problem is the SVI dose not come up even if i assigne a switch port to that vlan

with sh int bri telling the interface administrivly up protocol down

strnage with svi !!

any idea

thanks

I have this problem too.
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John Blakley Tue, 10/14/2008 - 05:45

Are you in routing?

Do a:

sh vlan brief to verify your vlan is there.

Then a:

sh run int vlan to verify your configuration on the interface.

Can you post the results?

Thanks,

--John

glen.grant Tue, 10/14/2008 - 06:11

You have to have an "active port" in that vlan which shows a connected status in order for the SVI to come up or it must be in an active trunk link . If the port that you assigned to that vlan is not active then the SVI will not come up .

andrew.butterworth Tue, 10/14/2008 - 06:15

Is the switchport you assigned to that VLAN up? The SVI will only go up if there is an access or trunk port up and in the STP forwarding state. If you have assigned an interface to the VLAN and it is down the SVI will remain down also.

Andy

Giuseppe Larosa Tue, 10/14/2008 - 10:10

Hello Marwan,

at least one switchport access port or trunk needs to be in STP forwarding state in order to have the SVI up/up otherwise you get up/down

This mechanism of linking SVI state to STP state of corresponding L2 Vlan is called autostate and is present in multilayer switches including C6500 in Hybrid Mode.

Sometimes the problem is the opposite an SVI stays up when you would like it to go down because some additional port is associated to the vlan and so there is no reaction to a link fault

This autostate can be disabled not sure if in all multilayer switch platform and sw versions.

We can say this makes the difference between an SVI and a loopback interface (the loopback is also isolated at layer 2 of course)

Hope to help

Giuseppe

Marwan ALshawi Tue, 10/14/2008 - 15:50

hi guys

thanks for ur reply

the thing is the vlan L2 is there as i mentioned

i can see the vlans with show vlan bri

i dont know whats the relation witht the vlan 1 as stated above iam sure it is not the case..

and also one of the posts above asked to assigne the vlan svi to access port but actully i dont need because this is mltilayer switch at ditstribution layer only for intervaln routing i use it

for Giuseppe which is very interesting

i forget to say

this switch is root bridg then all ports and trunks forwarding state runing MST

and HSRP active gateway

thats why i found it STRANGE!!

anyway i appreciate all ur responses

Giuseppe Larosa Tue, 10/14/2008 - 21:39

Hello Marwan,

I understand it is the root bridge but your trunk ports carry all vlans as by default or have you configured the list of vlans permitted on all of them ?

the new L2 vlan is listed in the output of sh vlan but can you see at least a port listed on the right or just it is said active ?

this can make the difference.

actually no: ports listed are only access ports

I've checked on one device

614 VL-VRF-PROD-14 active

no ports listed here but it is on some trunks and so the SVI is up/up

from sh int trunk

Port Vlans in spanning tree forwarding state and not pruned

Te4/1 1-5,100,200,>> 614

sh int vlan 614

Vlan614 is up, line protocol is up

Hardware is EtherSVI, address is 0019.a935.8240 (bia 0019.a935.8240)

Description: VRF-PROD-14

on c3750 you can verify with sh int trunk or sh int switchport

Hope to help

Giuseppe

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