HI!
The magic is more friquent then we want to hear about it.
The same problem trapped with my network.
We have two 650x with some 3750 stacks connected to it on 2x10 Gbit (EtherChan) .
To each of those 3750 are connectedby one else 3750 stacks on 2x1Gbit (EtherChan)
One "happy" day (3 days ago) ALL the NETWORK got a crazy - domaine is not accessible!
Network pings about 5 secconds, then not at all.
After some hours of braine rings and restarting everithing in different combinations we shut all the ports on the both 650x.
Then began to not shut by one stack. The A and B up - network works good. Pings are pingingin all the pings.
When we uped X stack -- IMXO!!! To est - all falt down.
So we localized the problem. Then we shut the X down-stack (1 G-trunk).
With X stack 10G the LAN works good.
So we break the X down-stack 1G and find out the one 3750 who was the monster.
The network works during some years and that is the first but very remember INCIDENT.
Now we are trying to find out what is the problem.
Neither MARS, neither IDS kill the anomalia! -???? Why?!
We have fixed the baginning: Flapping vlan 1 MAC-address on port 1G X-down stack,
then flapping MAC Y between 10G trunks, ports down, ports up and all of those are continuosly.
IS IT Spanning-tree Protocol slapping?
On Layer 2 we have:
access ports are in port-fast
all switches are in Rapid PVST
trunk-ports are with vlan-lists and fast trunks
What shall I do to prevent from these surprises?
And is this problem of cisco devices or somebody else?
