IPv6 - delay in 'ping6'

Hi,

(note I've obfuscated the ping address - it was only an example url! but forums wouldn't let me post!)

I have just switched to Zen -ie an Internet provider offering full dual stack IPv4/6 support, using a Fritzbox 7530 and am experiencing a delay , seemingly in name resolution, when using 'ping6'.

The same configuration is also supporting iOS, windows, linux, raspberry pi - and these devices all seem to work fine.

The symptom is:
'ping www DOT ibm DOT com' -> instant response, start getting icmp request/response
ping6 'www DOT ibm DOT com' -> About a 3-4s delay after typing the command before the pings start
ie:

Code Block 
$ ping6 www DOT ibm DOT com
... delay here ...
PING6(56=40+8+8 bytes) 2a02:8010:687f:0:2dbc:1ea2:a301:b111 --> 2a02:26f0:e8:491::b3a
16 bytes from 2a02:26f0:e8:491::b3a, icmp_seq=0 hlim=58 time=11.621 ms
16 bytes from 2a02:26f0:e8:491::b3a, icmp_seq=1 hlim=58 time=10.486 ms
16 bytes from 2a02:26f0:e8:491::b3a, icmp_seq=2 hlim=58 time=11.994 ms

The same behaviour is seen for other IPv6 sites such as ipv6.google.com

Using 'nslookup' I also get a delay:

```
$ nslookup
... delay actually occurs here

ipv6.google.com
Server: 192.168.178.1
Address: 192.168.178.1#53

Non-authoritative answer:
ipv6.google.com canonical name = ipv6.l.google.com.

```
That delay is almost as if it's reverse resolving itself - or a localhost issue?
All the ipv6 testers I've tried in a browser suggest my IPv6 config is fine, sites reachable
I don't notice delays in google chrome
If IPv4 is disabled no delays occur
The router is set to automatic IPv6 (with fast commit)
The macOS Wifi adapter is set to automatic for ipv6 (and dhcp for ipv4)
scutil --dns ends with

Code Block 
DNS configuration (for scoped queries)
resolver #1
search domain[0] : fritz.box
nameserver[0] : 192.168.178.1
nameserver[1] : fd00::2e91:abff:fe55:2d26
if_index : 5 (en0)
flags : Scoped, Request A records, Request AAAA records
reach : 0x00020002 (Reachable,Directly Reachable Address)

So ipv6 addresses are being requested

/etc/hosts has

Code Block 
##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##
127.0.0.1 localhost
::1 localhost
fe80::1%lo0 localhost
# End of section
192.168.178.48 pi4

Any ideas why the delay?

Once past that ipv6 and ipv4 are both working fine it seems (from limited tests so far)