Hi community,
we migrated a customer from his old 65xx core switches to new 4500X in VSS.
As exchange for the copper linecards in the chassis he got two stacks of the new 3750X, with three switches each.
The other access switches are still untouched, despite of configuration changes, some older 3750 stacks with 2 or 3 switches included.
Softwareversions
4500X: cat4500e-universalk9.SPA.03.04.00.SG.151-2.SG.bin
3750X: c3750e-universalk9-mz.150-2.SE4.bin
Old 3750: c3750-ipbase-mz.122-35.SE5.bin
Obviously all worked fine, but the customer complained about loads of these messages on his syslog server now, distributed over the whole campus/all stacks:
| Host 0021.9b5e.7176 in vlan 1 is flapping between port Po1 and port Fa1/0/11 |
Which what seems like a classic loop or anything like that isnt in fact a loop. This station is directly attached to Fa1/0/11 of this switch, and theres no other link to the rest of the infrastructure, just the channel Po1, with two memberinterfaces.
Looks like this way for all of the stacks:
Config on the coreswitches:
interface Port-channel113
description PORTCHANNEL 2GBit
switchport
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
interface TenGigabitEthernet1/1/3
description MEMBER-IF CU PO113 1GBit
switchport mode trunk
switchport nonegotiate
channel-protocol lacp
channel-group 113 mode active
spanning-tree portfast trunk
interface TenGigabitEthernet2/1/3
description MEMBER-IF LWL PO113 1Gbit
switchport mode trunk
switchport nonegotiate
channel-protocol lacp
channel-group 113 mode active
spanning-tree portfast trunk
(4500X-1 and 4500X-2)
VSS-Cluster
Te1/1/3 Te2/1/3
/ Po113 \
/ \
/ \
/ Po1 \
3750-1 \
\ \
3750-2 \ Stack 3x 3750 via stacking cables
\ \
3750-3
Config on the Stackswitches:
interface Port-channel1
description PORTCHANNEL TO VSS-CORE 2GBit -> PO1
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
spanning-tree portfast trunk
interface GigabitEthernet1/0/1
description LWL MEMBERLINK PO1 -> 4500X
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
load-interval 30
channel-group 1 mode active
spanning-tree portfast trunk
interface GigabitEthernet3/0/1
description LWL MEMBERLINK PO1 -> 4500X
switchport trunk encapsulation dot1q
switchport mode trunk
switchport nonegotiate
load-interval 30
channel-group 1 mode active
spanning-tree portfast trunk
These errormessages occur everywhere actually, also on the new stack with the 3750X.
I checked already and couldnt find:
- no messages regarding Loops on the core
- no messages or anything that at any given time one of the memberlinks left the channel
- no real problems recognized by users or management systems
I´m running out of ideas actually how i could solve that.
All i could find was regarding real loops, or ports leaving the channel...we don´t have THESE problems here.
And even more interesting is:
We have one more switch, which has no seperate stackmembers, and is connected with two interfaces to the VSS core...this switch expereinces exactly the same problem...a mac-address is learned over Po1 instead of the port this station is exactly patched to...so it obviously has nothing to do with the portchannes over different stackmodule-switches.
Many thanks in advance for the input,
Andreas
