Is the IP address 10.111.10.1 the IP address of the "inside" interface of the ASA? The ASA is receving a packet on the inside interface with a source IP which is it's own and the destination IP is that of the syslog server 10.99.100.1. Could you paste the output of "show route" and "show int ip brief" from the ASA?
Is the ASA sending syslogs to 10.99.100.1? If so, is it connected to the "inside" interface of the ASA? If so, it seems like the there is some kind of a routing loop in the network! The device directly connected to the ASA on the "inside" interface is sending this packet back to the ASA for some reason. Please have a look the device connected to the ASA on the inside interface.
Well as i said previously my guess is that The device directly connected to the ASA on the "inside" interface is sending this packet back to the ASA for some reason. Please apply captures on the ASA from the ASA to the syslogs server and vice versa on the inside interface as i had said.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...