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

[John Neiberger]

Also, another interesting thing about this is that the output of "show
ethernet mac-learning-log" stops at April 13th. I have no idea why. If a
MAC address were jumping around, we'd see it in the MAC learning log...if
it were up to date. What would cause a Juniper switch to stop logging to
the MAC learning log?

By the way, this is an EX4200 running 10.4R6.5.


On Fri, Jun 7, 2013 at 4:07 PM, John Neiberger <jneiberger at gmail.com> wrote:

> 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
>