I'm not aware of any inherent loop protection when running a VC setup that substitutes for STP.
Thanks, Morgan On Thu, May 29, 2014 at 7:35 AM, Jeff Meyers <[email protected]> wrote: > Hi everybody, > > recently we saw a strange bahviour in our network. A customer with a > Proxmox server had a Windows 2k8 VM with 2 virtual NICs (both bridged to > eth0 of the server which faces the internet) and bridged them together > INSIDE the VM. This caused immediately high latency and partial packet-loss > within the whole network with the following messages in the router log: > > May 29 04:06:33 cr0 l2ald[2545]: L2ALD_MAC_MOVE_NOTIFICATION: MAC Moves > detected in the system > > > This is all I saw, no other device detected anything suspicious. This is > the setup of the network: > > > MX480 router with DPCE and irb-interfaces but no (R)STP or any other STP > flavour. This router connects 2x 10G as ae0 to a virtual-chassis consisting > of 2x EX4550. This is a pure Layer2 device and the RSTP root bridge with > priority 0. Furthermore, each server room is equipped with 2x EX4200 in a > VC as well with a RSTP priority of 16k. The ToR switches might have RSTP > enabled or not and are usually connected with 1x GE to the EX4200 stack. > Here is a scheme which describes the setup hopefully good enough: > > > > +-------+ > | MX480 | ------- L3 edge-router, no STP > +-------+ > || ------- ae0 with 2x XGE > +----------------+ > | EX4550 | ------- L2 only > +----------------+ ------- RSTP priority 0 > | EX4550 | > +----------------+ > || || > +----------+ +----------+ > | EX4200 | | EX4200 | > +----------+ +----------+ ------- RSTP priority 16k > | EX4200 | | EX4200 | > +----------+ +----------+ > | | | ------- 1GE links to ToR > +-------+ +-------+ ... > | HP SW | | HP SW | ------- RSTP priority 32k > +-------+ +-------+ > ||||||| > |... > +--------------+ > | Proxmox Host | > +--------------+ > > > > In this particular scenario, the HP ProCurve switch had STP disabled and > did not participate in the spanning-tree protocol. However, for my > understanding that shouldn't be required anyways because the VC of the > EX4200 switches should identify a potential loop on their own as long as > there is no BPDU filter present. > The visible behaviour was high latency to several devices and sometimes up > to 100% packet-loss. Not only within the customer's vlan but globally in > every L2 segment. The arp count did not change on the router, I checked > that. No TC event was recognized by any device. The questions are now: > > - How is it possible that a bridge on a host with just ONE physical uplink > can cause such problems? > - Am I correct that RSTP on the ToR switches is not required as long as > they do not filter BPDUs? > > - Why would the MX router create such a message and indicate, that the MAC > changes although there is only one interface (ae0) facing the L2 network? > Even if a MAC moves on the EX4550 stack from one port to another, the MX > would never see that. > > > Please let me know if you need any further details. I am very curious to > find out what went wrong here. Do I have a misunderstanding on how STP > behaves in that scenario? Are there any ways to dig deeper into analysis of > the causes for that strange MX log message? > > > Thanks a lot! > > > Best regards, > Jeff > > _______________________________________________ > juniper-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/juniper-nsp > _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
