Noticed that even after a factory reset to defaults, the switch will will duplicate broadcast frames if the default vlan is attached to a L3 IRB interface. When two switches are connected, end hosts see 4 double frames instead of 1, the more switches in a chain the more multiplication of frames at the furthest switch. Noticed this behaviour on the EX3400, can anyone else confirm this on their end? Very easy to spot with DHCP messages.
I assume what is happening is that frame is being forwarded as any broadcast (or multicast) would, and is also being sent (copied) to RE, who then forwards it as well. As to why, that is a good question.
For DHCP packets, multiple copies should not be an issue. I assume you have no DHCP config of any type on the switch as well, yes?
Was what I was thinking also. No DHCP config on the switches. I noticed it because Cisco SPA phones refused to boot up, looks like there may be a bug on their firmware that causes the to lockup. Was hoping someone else from the community would be able to confirm this issue.
Firewall input rule on lo0 to discard packets sent to broadcast fixes the problem, looks like the IRB is definitely forwarding broadcast packets. I can also confirm this is happening regardless of the vlan and that this does not affect the EX2300-48P running 15.1X53-D55. Currently the switch in question is running 15.1X53-D55 but can confirm the problem is also present on D56. No service contract on the switch, working with the vendor to get it on there so that I can file a JTAC case.