Ok, thankyou so much, I seem to be making some progress.
For one minute in the system log I got these
Fri Feb 5 17:47:24 2021 kern.warn kernel: [191687.568386] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:25 2021 kern.warn kernel: [191688.572414] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:26 2021 kern.warn kernel: [191689.596465] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:31 2021 kern.warn kernel: [191694.760455] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:32 2021 kern.warn kernel: [191695.772514] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:33 2021 kern.warn kernel: [191696.796439] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:43 2021 kern.warn kernel: [191706.332604] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:43 2021 kern.warn kernel: [191706.343235] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:43 2021 kern.warn kernel: [191706.353472] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:47 2021 kern.warn kernel: [191710.452938] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:48 2021 kern.warn kernel: [191711.484568] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
Fri Feb 5 17:47:49 2021 kern.warn kernel: [191712.508647] br-lan: received packet on eth0 with own address as source address (addr:dc:a6:32:f2:38:1f, vlan:0)
and in tcpdump output, for the same minute, these
tcpdump -i eth0 -evn -Q in ether src host dc:a6:32:f2:38:1f
---- beginning of minute - some earlier ones removed
17:47:24.527705 dc:a6:32:f2:38:1f > 33:33:ff:71:a3:d3, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff71:a3d3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:c069:5f8:7a71:a3d3
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:25.531728 dc:a6:32:f2:38:1f > 33:33:ff:71:a3:d3, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff71:a3d3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:c069:5f8:7a71:a3d3
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:26.555765 dc:a6:32:f2:38:1f > 33:33:ff:71:a3:d3, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff71:a3d3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:c069:5f8:7a71:a3d3
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:31.719707 dc:a6:32:f2:38:1f > 33:33:ff:71:a3:d3, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff71:a3d3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:c069:5f8:7a71:a3d3
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:32.731758 dc:a6:32:f2:38:1f > 33:33:ff:71:a3:d3, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff71:a3d3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:c069:5f8:7a71:a3d3
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:33.755676 dc:a6:32:f2:38:1f > 33:33:ff:71:a3:d3, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff71:a3d3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:c069:5f8:7a71:a3d3
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:43.291746 dc:a6:32:f2:38:1f > 33:33:ff:f2:38:1f, ethertype IPv6 (0x86dd), length 86: (hlim 1, next-header Options (0) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:fff2:381f: HBH (rtalert: 0x0000) (padn) [icmp6 sum ok] ICMP6, multicast listener reportmax resp delay: 0 addr: ff02::1:fff2:381f
17:47:43.302383 dc:a6:32:f2:38:1f > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 86: (hlim 1, next-header Options (0) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:2: HBH (rtalert: 0x0000) (padn) [icmp6 sum ok] ICMP6, multicast listener reportmax resp delay: 0 addr: ff02::1:2
17:47:43.312629 dc:a6:32:f2:38:1f > 33:33:00:01:00:03, ethertype IPv6 (0x86dd), length 86: (hlim 1, next-header Options (0) payload length: 32) fe80::dea6:32ff:fef2:381f > ff05::1:3: HBH (rtalert: 0x0000) (padn) [icmp6 sum ok] ICMP6, multicast listener reportmax resp delay: 0 addr: ff05::1:3
17:47:47.412040 dc:a6:32:f2:38:1f > 33:33:ff:3f:89:84, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff3f:8984: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:387c:d840:583f:8984
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:48.443667 dc:a6:32:f2:38:1f > 33:33:ff:3f:89:84, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff3f:8984: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:387c:d840:583f:8984
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
17:47:49.467739 dc:a6:32:f2:38:1f > 33:33:ff:3f:89:84, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::dea6:32ff:fef2:381f > ff02::1:ff3f:8984: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2a00:23c4:a993:8700:387c:d840:583f:8984
source link-address option (1), length 8 (1): dc:a6:32:f2:38:1f
---- end of minute - the rest removed
25 packets captured
3250 packets received by filter
6 packets dropped by kernel
8 packets dropped by interface
It would appear that the number of lines are the same and the timing second is the same in each,
but....
what does it mean?
Thankyou
Richard