I disabled SVI on 4500x switch, network perfomance became unstable

[vciussnail]

Hi 

I'm planning to delete one inactive SVI (VLAN105-Wifi VLAN) and use it's subnet.

I tried to disable it first to check the behavior of the prod core switch.

My palm sweats instantly after shutting down the SVI seeing the behavior, my continuous ping to core became intermittent with high latency. I think the cpu process went high (not sure) 

So I put it back and enable the SVI to avoid any potential network problem.

It took time to establish but network became normal.

Any idea what would be the best aproach to delete that one vlan and avoid impacts?

Thanks in advance!

[balaji.bandi]

how is your network - any small diagram. (if possible post configuration)

along with below outout :

show version

show ip interface brief

show spanningtree root

show spanningtree block

show vtp status

[vciussnail]

Hi Balaji,

Please see details below

PHEXB201#sh spanning-tree root

Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
---------------- -------------------- --------- ----- --- --- ------------
VLAN0001 4097 0008.e3ff.fc28 0 2 20 15
VLAN0030 4126 0008.e3ff.fc28 0 2 20 15
VLAN0090 4186 0008.e3ff.fc28 0 2 20 15
VLAN0091 4187 0008.e3ff.fc28 0 2 20 15
VLAN0100 4196 0008.e3ff.fc28 0 2 20 15
VLAN0101 4197 0008.e3ff.fc28 0 2 20 15
VLAN0103 4199 0008.e3ff.fc28 0 2 20 15
VLAN0104 4200 0008.e3ff.fc28 0 2 20 15
VLAN0105 4201 0008.e3ff.fc28 0 2 20 15
VLAN0106 4202 0008.e3ff.fc28 0 2 20 15
VLAN0200 4296 0008.e3ff.fc28 0 2 20 15
VLAN0201 4297 0008.e3ff.fc28 0 2 20 15
VLAN0202 4298 0008.e3ff.fc28 0 2 20 15
VLAN0203 4299 0008.e3ff.fc28 0 2 20 15
VLAN0205 4301 0008.e3ff.fc28 0 2 20 15
VLAN0206 4302 0008.e3ff.fc28 0 2 20 15
VLAN0290 4386 0008.e3ff.fc28 0 2 20 15
VLAN0299 4395 0008.e3ff.fc28 0 2 20 15
VLAN0300 4396 0008.e3ff.fc28 0 2 20 15
VLAN0301 4397 0008.e3ff.fc28 0 2 20 15
VLAN0350 4446 0008.e3ff.fc28 0 2 20 15
VLAN0400 4496 0008.e3ff.fc28 0 2 20 15
VLAN0500 4596 0008.e3ff.fc28 0 2 20 15
VLAN0999 5095 0008.e3ff.fc28 0 2 20 15
PHEXB201#sh spanning-tree block

Name Blocked Interfaces List
-------------------- ------------------------------------

Number of blocked ports (segments) in the system : 0

PHEXB201#sh vtp status
VTP Version capable : 1 to 3
VTP version running : 1
VTP Domain Name : ESSPI
VTP Pruning Mode : Disabled
VTP Traps Generation : Enabled
Device ID : 0200.0000.000a
Configuration last modified by 192.168.2.1 at 0-0-00 00:00:00

Feature VLAN:
--------------
VTP Operating Mode : Transparent
Maximum VLANs supported locally : 1005
Number of existing VLANs : 28
Configuration Revision : 0
MD5 digest : 0x03 0x08 0x45 0x6F 0x2F 0x68 0xC2 0x78
0x4B 0x93 0x66 0x90 0x95 0xC2 0x65 0x5E
PHEXB201#sh version
Cisco IOS Software, IOS-XE Software, Catalyst 4500 L3 Switch Software (cat4500e-UNIVERSAL-M), Version 03.08.03.E RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Sun 06-Nov-16 15:25 by prod_rel_team

Cisco IOS-XE software, Copyright (c) 2005-2015 by cisco Systems, Inc.
All rights reserved. Certain components of Cisco IOS-XE software are
licensed under the GNU General Public License ("GPL") Version 2.0. The
software code licensed under GPL Version 2.0 is free software that comes
with ABSOLUTELY NO WARRANTY. You can redistribute and/or modify such
GPL code under the terms of GPL Version 2.0.
(http://www.gnu.org/licenses/gpl-2.0.html) For more details, see the
documentation or "License Notice" file accompanying the IOS-XE software,
or the applicable URL provided on the flyer accompanying the IOS-XE
software.

ROM: 15.0(1r)SG12
PHEXB201 uptime is 3 years, 28 weeks, 2 days, 5 hours, 9 minutes
Uptime for this control processor is 3 years, 3 weeks, 3 days, 11 hours, 37 minutes
System returned to ROM by SSO Switchover
System restarted at 09:08:41 MNL Sat Jan 6 2018
System image file is "flash1:unknown"
Jawa Revision 3, Winter Revision 0x0.0x41

Last reload reason: Reload command

License Information for 'WS-C4500X-32'
License Level: ipbase Type: Permanent
Next reboot license Level: ipbase

cisco WS-C4500X-32 (MPC8572) processor (revision 9) with 4194304K bytes of physical memory.
Processor board ID JAE211706CE
MPC8572 CPU at 1.5GHz, Cisco Catalyst 4500X
Last reset from PowerUp
17 Virtual Ethernet interfaces
64 Ten Gigabit Ethernet interfaces
511K bytes of non-volatile configuration memory.

Configuration register is 0x2101

[balaji.bandi]

As per the input and we are not sure how big is the network - i believe  Spanning tree convergence hitting with convergence times.

So remove the VLAn From spanning tree, Shut the interface and see any other issue, and remove the interface, and remove VLAN also if not required any more.

also worth checking show ip arp for the VLAN see anything associated.

[vciussnail]

Hi Balaji,

I shutdown the interface and delete the vlan105. Latency and performance still the same.

Pending action on my side is to delete spanning-tree vlan105.

My question is, is there any impact for deleting spanning-tree vlan105?

[Georg Pauwen]

Hello,

the instability probably is caused the spanning tree (after all, you are deleting a Vlan). Depending on whether or not you use VTP, you might want to prune the Vlan. If that is not an option, you could try and remove the Vlan from spanning tree altogether:

no spanning-tree vlan 105

and then delete both the SVI and the Vlan:

interface Vlan 105

--> shut

!

no interface Vlan 105

no vlan 105

[vciussnail]

Hi Georg,

What would be the impact if I execute no spanning-tree vlan 105?

[Georg Pauwen]

Hello,

none, if there are no active clients on the WiFi Vlan (105) you want to delete.