IRF ARP-MAD detection - question

[Michal Doležal]

Question is really simple, is possible to traverse ARP-MAD traffic accross more switches?

I have two switches in site A (connected together with CX4) and one switch in site B, all connected to IRF ring-topology. There is 160m distance between Site A and B. So two 160m long opt. cables are connected from Switch 1 to 3 and Switch 2 to 3.

I need to solve the situation where switch 3 on Site B is disconnected from both 10Gbit lines between Site A and B.

Site A can be controlled using BFD MAD, or LACP MAD, but I need also to check Site B.

I have MSTP configured so ARP MAD can be solution. But the line between Site A and B goes accross more the one switch. (not an IRF line, but data line)

In current situation I achieve the state where when split occurr then all STP configured ports on switch 3 is going to DISCARDING state so the switch is completely isolated. But this is not normal behavior of IRF MAD, port must be shutdown (all ports - excluded ports)

The 3rd switch becomes Master and is forwaring only locally (with blocked uplinks), this can be used but it is not desired state for customer.

I configured mad arp enable, define VLAN for MAD, define IP adress on IRF Core and propagate VLAN over upliks to intermediate switches.

Any idea?

[Michal Doležal]

And quite simple is also the solution. The problem is with STP root protection. Without it ARP MAD is functioning properly. It looks that STP Root protection is faster than ARP MAD. IRF switch is acting as MSTP Core, so I setup manually STP root priority to 0. When split occured than two STP Roots exists on the network one as current IRF stack (2 members) and one as splitted switch with new MAC address (STP Bridge address). Because Bridge mac address of IRF Stack was lower than MAC of splitted switch. So all ports of splitted switch was in state Discarding (so no packets come into and also ARP MAD packets). When I switch the root-protection off ARP MAD normally shutdown the ports on splitted switch and the IRF state was recovering. So in this case when you need to guard STP root and together guard IRF stack I don´t know the exact way how to do this. Some ideas?