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Strange issue with new Cisco Catalyst 2960 (IOS)

Hello all,

I am upgrading a older 2950(100M) switch replacing it with a gigabit 2960. Installed it in the same rack, the configuration is practically non-existent just set the passwords and IP. We run a single VLAN flat network for this so I started out by patching it to the existing switch, after a few days we had an opportunity to migrate because there was some downtime so I disconnected the cables on the old and moved them to the new.. Everything seemed fine, there is connectivity and things operate, but a few days later we noticed that some network transfer activities are slow. There are no errors or log entries showing on the new switch or the old one, but the low throughput is persistent.

All ports show 1G Full duplex as they should, but what I see when I test is that traffic tests look almost asynchronous when passing switch boundaries with normal read speeds and slow writes. Reversing the direction of the test hosts I get slow reads and fast writes so it seems to 'stick' to one side of the traffic path. Testing the same equipment against differente targets without the switch boundary crossing does not show the problem. All Intra-switch tests look good (gig switches transfer near a gig and 100 switches near 100), but the moment there is a crossing things behave strangely regardless of the target (new switch is center backbone with most hosts, but does no routing). Network layout is essentially a T with everything radiating from the new switch. I can eliminate the old switch soon, but I still need to resolve the problem with the crossing to the other switch.

Everything seems to point at the inter switch links. One is a patch cable under two feet, and the other is a dedicated fiber site link. We had the vendor confirm that the site link showed no issues, but having the same symptoms on both links makes me suspect the switch has something odd happening..

I checked for duplex issues first, but didn't find any. I flushed the arp caches in all of the switches (3 total) and all of the computers as well, but the problem persists.

Could this be an STP issue ?   If so how can I set this switch as the STP root and force a refresh..

Any help would be greatly appreciated.

  • LAN Switching and Routing
Everyone's tags (1)
40 REPLIES

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Another detail.. Just dis show spanning-tree on all switches and two claim to to be the spanning-tree root. The new switch in the center is the only one that does not. Another oddity I see ist that the two directly connected switches see each other as CDP neighbors, but the one across the fiber link does not see any neighbors. IP traffic is flowing, but this has me more worried all the time.

Green

Strange issue with new Cisco Catalyst 2960 (IOS)

David,

This does sound worrying.

There should only be ONE root bridge for your whole

flat vlan.

Can you share your config and a network diagram with us.

Regards,
Alex.
Please rate useful posts.

Regards, Alex. Please rate useful posts.

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Hello

Can you post a topology of you network and specify the location of the old/nre switch

Also a running config of the new switch?

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

Please don't forget to rate any posts that have been helpful. Thanks.

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

The network looks like this (very simple)

C2950 (Pt Fas 0/22) <---Patch---> (port Gi1/0/48) C2960G (port Gi1/0/47) <--- Fiber ---> C2960 Si (port Gi0/2)

                                                                             !

                                                                             !

                                                                             !

                                                            Firewall and default gateway (Cisco 2901)

Both ends say they're STP root. CDP doesn't cross fiber (I think it's a tunnel in cisco at provider)

Below is the running config (paswords removed and repetitive elements removed). Fixed speed port(47) is fiber link, patch to 2950 is port 48.

CISCO-2960-48-GB-ASP#show running-config

Building configuration...

Current configuration : 4151 bytes

!

version 12.2

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname CISCO-2960-48-GB-ASP

!

boot-start-marker

boot-end-marker

!

enable secret 5 ******************

enable password  ****************

!

!

!

no aaa new-model

switch 1 provision ws-c2960s-48td-l

!

!

!

!

crypto pki trustpoint TP-self-signed-3269237632

enrollment selfsigned

subject-name cn=IOS-Self-Signed-Certificate-3269237632

revocation-check none

rsakeypair TP-self-signed-3269237632

!

!

crypto pki certificate chain TP-self-signed-3269237632

certificate self-signed 01

(CERT BINARY REMOVED)

  quit

spanning-tree mode pvst

spanning-tree extend system-id

!

!

!

!

vlan internal allocation policy ascending

!

!

!

interface FastEthernet0

no ip address

!

interface GigabitEthernet1/0/1

!

(ALL PORTS AUTO TO THIS POINT)

!

interface GigabitEthernet1/0/46

!

interface GigabitEthernet1/0/47

speed 100

duplex full

!

interface GigabitEthernet1/0/48

!

interface GigabitEthernet1/0/49

!

interface GigabitEthernet1/0/50

!

interface TenGigabitEthernet1/0/1

!

interface TenGigabitEthernet1/0/2

!

interface Vlan1

ip address 192.168.0.25 255.255.255.0

!

ip http server

ip http secure-server

!

line con 0

line vty 0 4

password  ****************

login

line vty 5 15

password  ***************

login

!

end

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Hello

Have you checked the cabling?

What IOS are you running?

also try this:

spanning-tree vlan 1 priority 0

spanning-tree portfast bpduguard default

ip default-gateway

access ports

switchport host

no cdp enable

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

Please don't forget to rate any posts that have been helpful. Thanks.

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Hi Paul,

Checked cabling and also had provider confirm ports weren't flapping or generating errors on either end from his side. The switches are all logging at debug level and show no problems or flapping either. Swapped ports on the far right switch, but not on the others (could only be at one site at a time).

Before trying that a question: is there a chance it would lock me out (I am remote at the moment)

Also- the gateway probably wouldn't affect it either its all a single IP subnet with private addresses roughly 30 systems.

The IOS may be an issue on the oldest switch.. here are show ver of each (slightly abridged):

Oldest  C2950-

Cisco Internetwork Operating System Software

IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA2, RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2004 by cisco Systems, Inc.

Compiled Sun 07-Nov-04 23:14 by antonino

Image text-base: 0x80010000, data-base: 0x8055E000

ROM: Bootstrap program is C2950 boot loader

uptime is 5 years, 7 weeks, 3 days, 6 hours, 54 minutes

System returned to ROM by power-on

System image file is "flash:/c2950-i6q4l2-mz.121-22.EA2.bin"

cisco WS-C2950-24 (RC32300) processor (revision R0) with 21055K bytes of memory.

Processor board ID FOC0908W1ZQ

Last reset from system-reset

Running Standard Image

24 FastEthernet/IEEE 802.3 interface(s)

Newest C2960 Gig-

Cisco IOS Software, C2960S Software (C2960S-UNIVERSALK9-M), Version 12.2(55)SE7, RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2013 by Cisco Systems, Inc.

Compiled Mon 28-Jan-13 10:28 by prod_rel_team

Image text-base: 0x00003000, data-base: 0x01B00000

ROM: Bootstrap program is Alpha board boot loader

BOOTLDR: C2960S Boot Loader (C2960S-HBOOT-M) Version 12.2(55r)SE, RELEASE SOFTWARE (fc1)

uptime is 11 weeks, 3 days, 21 hours, 1 minute

System returned to ROM by power-on

System image file is "flash:/c2960s-universalk9-mz.122-55.SE7/c2960s-universalk9-mz.122-55.SE7.bin"

cisco WS-C2960S-48TD-L (PowerPC) processor (revision J0) with 131072K bytes of memory.

Processor board ID FOC1718W11Q

Last reset from power-on

1 Virtual Ethernet interface

1 FastEthernet interface

50 Gigabit Ethernet interfaces

2 Ten Gigabit Ethernet interfaces

Switch Ports Model              SW Version            SW Image

------ ----- -----              ----------            ----------

*    1 52    WS-C2960S-48TD-L   12.2(55)SE7           C2960S-UNIVERSALK9-M

Far Right C2960 on other side of Fiber-

Cisco IOS Software, C2960 Software (C2960-LANLITEK9-M), Version 12.2(50)SE5, RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2010 by Cisco Systems, Inc.

Compiled Tue 28-Sep-10 13:44 by prod_rel_team

Image text-base: 0x00003000, data-base: 0x01200000

ROM: Bootstrap program is C2960 boot loader

BOOTLDR: C2960 Boot Loader (C2960-HBOOT-M) Version 12.2(53r)SEY3, RELEASE SOFTWARE (fc1)

uptime is 51 weeks, 6 days, 2 hours, 19 minutes

System returned to ROM by power-on

System image file is "flash:/c2960-lanlitek9-mz.122-50.SE5/c2960-lanlitek9-mz.122-50.SE5.bin"

cisco WS-C2960-24TC-S (PowerPC405) processor (revision P0) with 65536K bytes of memory.

Processor board ID FCQ1623Y1QC

Last reset from power-on

1 Virtual Ethernet interface

24 FastEthernet interfaces

2 Gigabit Ethernet interfaces

Switch Ports Model              SW Version            SW Image

------ ----- -----              ----------            ----------

*    1 26    WS-C2960-24TC-S    12.2(50)SE5           C2960-LANLITEK9-M

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Hello

"The switches are all logging at debug level and show no problems or  flapping either"

If you mean debugging is enabled on the switches, please turn it off ASAP- this can a have a major effect on the switches performance

undebug all

Also the changes I have specified shouldn't have any effect on the switch or network if you say that this switch is already the STP root. - however I would suggested checking again prior to applying the config.

sh spanning-tree root

The access config is to be applied only on the access ports, if you have unauthorized switch devices attached to any of these porst then they could be errdisabled by the bpduguard feature.

Apart from  I cannot see any issues.

If you dont feel comfortable doing this remotely then refrain from doing so and apply the changes when you are physically present or  save you current running config and execute a timed reload prior to any changes.

wr

reload in xx

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

Please don't forget to rate any posts that have been helpful. Thanks.

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Paul,

Sorry for the delay, in different timezone was going home and sleeping.

Just meant that the logging level is 7 (debugging).

    Console logging: level debugging, 743 messages logged, xml disabled,

                     filtering disabled

    Monitor logging: level debugging, 0 messages logged, xml disabled,

                     filtering disabled

    Buffer logging:  level debugging, 743 messages logged, xml disabled,

                     filtering disabled

The new switch is not the spanning tree root.. The two other switches are both claiming to be. I will try lowering the priority value on the new switch as soon as I can make a trip, I prefer to be there just in case.  May go today, but worst case it will be over the weekend.

I don't have trunk mode enabled because there are no VLANs, but I was also worried by the remote switch not seeing the new switch as a CDP neighbor and also claiming to be an STP root.. IP is flowing between, but it's not what I expected to see mit looks rather like the switches don't recognize each other fully. Is that normal for a remote switch ?

Dave

Re: Strange issue with new Cisco Catalyst 2960 (IOS)

Hello

Trunking doesnt matter in this case as you are correct if only the default vlan is being used.

However I dont understand what you mean by the remote switch?

Also

The new switch is not the spanning tree root.. The two other switches are both claiming to be -  This is a bit concerning as isnt this new switch  interconnected between these two other switches  claiming to be stp root?

Can you post the following config for all 3 switches:

show spanning-tree vlan 1

(These will be the interconect links between the switchs)

sh run int xx

sh int xx

sh int xx switchport

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

Please don't forget to rate any posts that have been helpful. Thanks.
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