Communication problem between Cisco 8500-12x and Fortigate

[User24571]

Hello,

I have a communication problem between Cisco 8500-12X and Fortigate Firewall. 

The problem is that both devices suddenly stopped communicating with each other (they do not respond to ICMP - on FW I allowed ICMP packets) Of course, no other traffic goes through either.
Interestingly, the MAC addresses are refreshing.
On the router I have implemented L2 on bridge-domain.

Topology:
Fortigate (Public IP) ---- (int BDI) Cisco 8500-12X -- ISP

On the router I have recommended software: 17.09.04a

[M02@rt37]

@User24571 

Do you diagnose on Fortigate side ? I mean, diagnose sniffer packet in CLI to see if icmp echo-request from C8500 arrived on that FortiGate ?

[MHM Cisco World]

So c8500 use BDI and or L3 interface BVI, 

Thr FPR use pppoe?

That correct

If yes then check your routing table in fpr

MHM

[balaji.bandi]

To make sure what device having this issue-

try below

PC ---- (int BDI) Cisco 8500-12X -- ISP  ( does the PC able to work as expected )

from there you know where to start troubleshooting

[User24571]

Thank you for all your ideas, but the problem lay elsewhere
It turned out that two Fortigate clusters present themselves with the same MAC address.

[balaji.bandi]

is this HA  ? then try turn off one of the node and check ?