collisions in a vlan interface

[Cooky]

We're experiencing slow network on a particular switch.
When I was going through the sh interface, I noticed bunch of collisions under int vlan1. What exactly does that number represent?
Sum of all collisions of the physical interfaces in the same vlan?

 

[spidey07]

oooohhhh....that's bad. You shouldn't have any errors on a vlan interface as it's virtual. An SVI.

post "show int vlan 1", "show queueing vlan 1", "show int stats"

and the model of switch and if any L3/L4 switching or ACLs/VACLs are being used.

 

[Cooky]

I'll have to get the show outputs from work on Monday...forgot which switch it is.
Model is an aging 3548XL. No multi-layer switching is used (model doesn't support it anyway).

We checked couple of other switches in the same site, and they have the same number of collisions on the vlan1 interface. Does that indicate how many collisions in our vlan1 collision domain??
And how bad is it to have collision on a vlan int?

 

[spyordie007]

Dumb question but how many is "a bunch"; and how long since you've last cleared counters? I'm assuming that the collisions are still incrementing.

100 collisions that occurred during some freak network issue 2 years ago might not make any difference today 😉

Might also be useful if you posted your config (just blank out any parts you can?t let the public see). Also let us know what version of IOS it's running.

I've never heard of collisions on a VLAN Interface so not sure how to troubleshoot. If it were in my deployment I'd just hand it off to one of our CCIEs 😀

 

[Cooky]

007, I'll have to answer your questions on Monday cause I don't have access to that switch right now.
Assuming the stats are current, how is it bad, and what can I do to fix it?
Out of about 30 switches in that site, only that particular was experiencing problem. We checked the config and it looked fine. (will post on Mondy too)

 

[spidey07]

Could be an IOS bug, because I can't think of any reason why you would ever have them on an SVI.

You should have maintenance on all your gear so you could just call TAC.

 

[Cooky]

Unfortunately it's impossible to get SmartNet on all access switches, but only cores...

 

[Cooky]

AiC1-SWHA-8-73#sh int vlan1
VLAN1 is up, line protocol is up
Hardware is CPU Interface, address is 0030.7172.ac40 (bia 0030.7172.ac40)
Description: Management - VLAN 1
Internet address is 10.x.x.x/23
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 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 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 5d16h
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 2 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
33462 packets input, 2630311 bytes, 0 no buffer
Received 19872 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
13631 packets output, 1626841 bytes, 0 underruns
0 output errors, 1333002353 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

 

[Cooky]

IOS 12.0(5)XP
Model WS-C3548-XL-EN
---------------
version 12.0
no service pad
service timestamps debug datetime localtime
service timestamps log datetime localtime
service password-encryption
!
hostname AiC1-SWHA-8-73
!
logging buffered 12288 errors
no logging console
aaa new-model
aaa authentication login default group tacacs+ enable
aaa authorization exec default group tacacs+ if-authenticated
aaa accounting exec default start-stop group tacacs+
aaa accounting commands 1 default wait-start group tacacs+
aaa accounting commands 15 default wait-start group tacacs+
enable secret 5 $$$$$$
!
!
!
!
!
clock timezone EST -5
clock summer-time EDT recurring
!
ip subnet-zero
no ip domain-lookup
!
!
!
interface FastEthernet0/1
no logging event link-status
switchport access vlan xxx
spanning-tree portfast
!
interface FastEthernet0/48
no logging event link-status
switchport access vlan xxx
spanning-tree portfast
!
interface GigabitEthernet0/1
description AiC1-SWHD-8-29 0/6
duplex full
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface GigabitEthernet0/2
shutdown
!
interface VLAN1
ip address 10.x.x.x 255.255.254.0
no ip directed-broadcast
no ip route-cache
!
ip default-gateway 10.x.x.x
no ip http server
logging x.x.x.x
snmp-server engineID local 00000009020000307172AC40
snmp-server community xxxx RO
snmp-server chassis-id 0x17
snmp-server host x.x.x.x trap xxxx
tacacs-server host x.x.x.x
tacacs-server host x.x.x.x
tacacs-server key xxxx
banner motd ^C
This system is for the use of authorized users only. Individuals using
this network device are subject to having all of their activities on this
system monitored and recorded. Anyone using this system expressly consents
to such monitoring and is advised that if such monitoring reveals possible
evidence of criminal activity, it may be provided as evidence to law
enforcement officials.^C
!
line con 0
exec-timeout 5 0
password 7 xxxx
transport input none
stopbits 1
line vty 0 4
exec-timeout 20 0
password 7 xxxx
line vty 5 15
!
ntp clock-period 11258905
ntp server 10.x.x.x
end

 

[spidey07]

If it is showing performance problems, and it's only that switch - I'd have a nother switch swapped with it to see if it continues.

May be hardware related. Also you can have a console cable connected to it and power cycle it to view the self tests. command line is "show post"

 

[Cooky]

We thought about looking at the post, but the switch is in a remote site, and it's quite a hassle to ask someone else to hook up a laptop that's got a serial port to console in.
Three other 3548XLs in the same closet don't have the same issue, and we think this may be hardware related like you said...