[j-nsp] What is this ethernet switching trace telling us?

[John Neiberger]

We're trying to troubleshoot an odd issue and this log output makes it
appear that a MAC address is flipping between interfaces. There are other
interfaces involved later in the logs. I'm starting to think this isn't
telling us what we think it's telling us. Does this indicate that the MAC
address really is being learned from multiple interfaces? The confusing
thing about the logs is the mention of l3nh. Is that layer three next hop?
If so, why are we seeing that in ethernet-level trace options and what is
the significance?

I'm a little confused. Here is an example:

Jun  4 13:07:22.953201 Attempt to add vlan sbc-core mac 00:08:25:fa:3c:82,
ifname ge-0/0/6.0, pnac_status 0, 0
Jun  4 13:07:22.953312 vlan sbc-core mac 00:08:25:fa:3c:82 (tag 40), iif =
ge-0/0/6.0: present in FDB
Jun  4 13:07:22.953374 (3, 00:08:25:fa:3c:82) next-hop index change [1344
-> 1328]
Jun  4 13:07:22.953562 KRT enqueue FDB (3, 00:08:25:fa:3c:82) nh-index 1328
Jun  4 13:07:22.953712 krt_dequeue: type FDB op change 3, 00:08:25:fa:3c:82
Direct nh 1328
Jun  4 13:07:22.954372 l3nh_fdb_notify: FDB CHANGE vlan <sbc-core> mac
00:08:25:fa:3c:82
Jun  4 13:21:18.041160 Attempt to add vlan sbc-core mac 00:08:25:fa:3c:82,
ifname ge-0/0/5.0, pnac_status 0, 0
Jun  4 13:21:18.041271 vlan sbc-core mac 00:08:25:fa:3c:82 (tag 40), iif =
ge-0/0/5.0: present in FDB
Jun  4 13:21:18.041332 (3, 00:08:25:fa:3c:82) next-hop index change [1328
-> 1327]
Jun  4 13:21:18.041670 Attempt to add vlan sbc-core mac 00:08:25:fa:3c:82,
ifname ge-0/0/6.0, pnac_status 0, 0
Jun  4 13:21:18.041767 vlan sbc-core mac 00:08:25:fa:3c:82 (tag 40), iif =
ge-0/0/6.0: present in FDB
Jun  4 13:21:18.041807 (3, 00:08:25:fa:3c:82) next-hop index change [1327
-> 1328]
Jun  4 13:21:18.041962 KRT enqueue FDB (3, 00:08:25:fa:3c:82) nh-index 1328

It looks to me like the MAC address is jumping around. What do you think?

Thanks,
John