This is what happens without dad-attempts 0 on br0:
Oct 13 10:31:30 westogre pppd[2055]: rcvd [IPCP ConfAck id=0x2 <addr
81.x.x.x>]
Oct 13 10:31:30 westogre pppd[2055]: local IP address 81.x.x.x
Oct 13 10:31:30 westogre pppd[2055]: remote IP address 81.187.81.187
Oct 13 10:31:30 westogre pppd[2055]: Script /etc/ppp/ip-up started (pid
2087)
Oct 13 10:31:30 westogre pppd[2055]: rcvd [IPV6CP ConfReq id=0x0 <addr
fe80::0203:97ff:fe40:4000>]
Oct 13 10:31:30 westogre pppd[2055]: sent [IPV6CP ConfAck id=0x0 <addr
fe80::0203:97ff:fe40:4000>]
Oct 13 10:31:30 westogre pppd[2055]: local LL address
fe80::4094:d1c2:9863:b1a5
Oct 13 10:31:30 westogre pppd[2055]: remote LL address
fe80::0203:97ff:fe40:4000
Oct 13 10:31:30 westogre pppd[2055]: Script /etc/ppp/ipv6-up started
(pid 2088)
Oct 13 10:31:30 westogre pppd[2055]: Script /etc/ppp/ipv6-up finished
(pid 2088), status = 0x0
Oct 13 10:31:31 westogre ifup[1521]: /bin/run-parts --exit-on-error
--verbose /etc/network/if-up.d
Oct 13 10:31:31 westogre ifup[1521]: run-parts: executing
/etc/network/if-up.d/bind9
Oct 13 10:31:31 westogre ifup[1521]: run-parts: executing
/etc/network/if-up.d/ethtool
Oct 13 10:31:31 westogre ifup[1521]: run-parts: executing
/etc/network/if-up.d/mountnfs
Oct 13 10:31:31 westogre ifup[1521]: /bin/run-parts --exit-on-error
--verbose /etc/network/if-up.d
Oct 13 10:31:31 westogre ifup[1521]: run-parts: executing
/etc/network/if-up.d/bind9
Oct 13 10:31:31 westogre ifup[1521]: run-parts: executing
/etc/network/if-up.d/ethtool
Oct 13 10:31:31 westogre ifup[1521]: run-parts: executing
/etc/network/if-up.d/mountnfs
Oct 13 10:31:31 westogre systemd[1]: networking.service: Main process
exited, code=exited, status=1/FAILURE
Oct 13 10:31:31 westogre pppd[2055]: Terminating on signal 15
Oct 13 10:31:31 westogre pppd[2055]: Connect time 0.1 minutes.
Oct 13 10:31:31 westogre pppd[2055]: Sent 242 bytes, received 0 bytes.
Oct 13 10:31:31 westogre pppd[2055]: Script /etc/ppp/ipv6-down started
(pid 2170)
Oct 13 10:31:31 westogre pppd[2055]: sent [LCP TermReq id=0x2 "User
request"]
Oct 13 10:31:31 westogre pppd[2055]: Child process /etc/ppp/ip-up (pid
2087) terminated with signal 15
Oct 13 10:31:31 westogre pppd[2055]: Script /etc/ppp/ip-down started
(pid 2171)
Oct 13 10:31:31 westogre pppd[2055]: Script /etc/ppp/ipv6-down finished
(pid 2170), status = 0x0
Oct 13 10:31:31 westogre pppd[2055]: rcvd [LCP TermAck id=0x2]
Oct 13 10:31:31 westogre pppd[2055]: Connection terminated.
Oct 13 10:31:31 westogre pppd[2055]: Connect time 0.1 minutes.
Oct 13 10:31:31 westogre pppd[2055]: Sent 242 bytes, received 0 bytes.
Oct 13 10:31:31 westogre pppd[2055]: Send PPPOE Discovery V1T1 PADT
session 0x214 length 20
Oct 13 10:31:31 westogre pppd[2055]: dst 28:8a:1c:e9:c0:52 src
00:19:99:ed:01:9a
Oct 13 10:31:31 westogre pppd[2055]: [AC-cookie 33 58 9a 5b 57 42 46
f7 fc e5 5e 6f d0 b3 47 8c]
Oct 13 10:31:31 westogre pppd[2055]: Sent PADT
Oct 13 10:31:31 westogre pppd[2055]: Waiting for 1 child processes...
Oct 13 10:31:31 westogre pppd[2055]: script /etc/ppp/ip-down, pid 2171
Oct 13 10:31:31 westogre pppd[2055]: Script /etc/ppp/ip-down finished
(pid 2171), status = 0x1
Oct 13 10:31:31 westogre pppd[2055]: Exit.
Oct 13 10:31:31 westogre systemd[1]: networking.service: Failed with
result 'exit-code'.
Oct 13 10:31:31 westogre systemd[1]: Failed to start Raise network
interfaces.
Oct 13 10:31:31 westogre systemd[1]: Reached target Network.
The irony of this is that br0 is configured absolutely fine, it's ppp0
that suffers!
