FredM

Hi all, We are using the component TIdIpMcastClient class for a UDP client that joins a Multicast group (ff02::3 in our case). We have 2 ethernet interfaces (one with index 16, one with index 17). As prescribed, we fill in the IPV6 address of one of the interfaces to make sure the group is joined on the interface of choice. Now, the problem is that whatever we do, we always join the mcast group on the same interface (16), but we also want to join the group on the other interface (17). Below you can see that on interface 16 the group ff02::3 is joined, but we used the IP address of interface 17, where there is no trace of group ff02::3 (see second image below). Important note: when we fully disable interface 16, we áre able to join interface 17. Then after enabling 16 again, it is not possible to join 16 anymore. Here's our delphi code: Using: Delphi 10.3, update 2 Indy 10 Thank you for your help! Fred

Hi Remy, Thank you for your answer, much appreciated! Now, the binding to the interface index itself it not so important. As long as we can bind to a specific interface, it is not important how. In fact, we currently use the interface IP address. I mention the interface indexes just to give you a better idea what's going on. So e.g. interface 16 has ip address: fe80::1c64:aff:fec8:7fe6 interface 17 has ip address fe80::2cad:26ff:fe8f:bfca We set fe80::2cad:26ff:fe8f:bfca as the IP address of interface (17) to bind to, but it just binds to interface 16 for some reason. We saw this thread online, it does seem related (even though it's not Indy): https://www.codenewsfast.com/cnf/article/0/permalink.art-ng1921q7387 What do you think?