FQDN node and icmp monitor

I can't as well figure out how Down Interval works.

According to manual

In the Down Interval field, type the number of seconds the system waits to mark an FQDN node down following a DNS query failure.

First of all what is considered DNS query failure?

• No records returned for FQDN query
• No reply from DNS server at all

From my test it looks like status change for non ephemeral node are like that (same order as above events):

• The DNS server(s) are available; No records returned 2017-06-05 09:59:00
• The DNS server(s) are unavailable

Now which node is set down by Down Interval? Non Ephemeral node or ephemeral node?

Seems that first as only log entries are for non ephemeral node, for ephemeral I can't see anything.

If ephemeral nodes has monitor assigned (via parent node) and there is reply from nodes there is situation when parent node is marked down (red diamond) but ephemeral up (green dot).

A bit confusing situation.

I guess if anyone noticed such issue:

• Monitor assigned to parent node
• Config saved
• Entering node again - no entry in Active monitors - or rather there is entry but without monitor name - but monitor is working and listed when list ltm node is performed.

I did some test for case when DNS is not reachable at all using tcpdump and ltm log.

Down Interval set to 5s

Results:

13:23:14.723097 ARP, Request who-has 10.128.11.4 tell 10.128.11.10, length 35 out slot1/tmm0 lis= - last arp request for DNS IP

Jun 5 13:23:25 bigiptest notice bigd[13757]: 01060141:5: Node /Common/lamp4-20_nd monitor status down [ 10.128.11.2: up ] [ was up for 0hr:2mins:21sec ]

Jun 5 13:23:25 bigiptest notice bigd[13757]: 01060141:5: Node /Common/lamp4-20_nd monitor status down [ 10.128.11.4: down ] [ was up for 0hr:2mins:21sec ] - ltm log entries

Form above it looks like non ephemeral node is going down after 11s - why so? Why not 5s?

Piotr