Problem is related to the presence of integrated routing & bridging if I delete the bridge virtual interface,disable bridging and give the two Gigabit Ethernet ports their own IP addresses, the multicast reception works correctly all received multicast packets have te expected value on the destination MAC address (matching the group address) However, subsequent packets' Ethernet headers have the wrong MAC address 01:00:5E:00:00:00 (the last three octets are all zeroes and these packets are discarded by Windows on the receiving PC and not seen by the multicast application. The first packet's Ethernet header contains the correct destination MAC address 01:00:5E:aa:bb:cc where aa:bb:cc match with the last three octets of the mulicast group's address, and that packet is received OK by the listening multicast application (c) But, there is an error in the Ethernet packets (b) Multicast routing on the WAN is working correctly running Wireshark on the receiving PCs shows that multicast data is received on the expected group. work correctly at the sender and at the other two PCs receiving the multicast stream Problem occurs when a (IPV4) multicast application on one PC communicates with the others: Multicast routing strategy between the routers is as per 'Anycast - Static RP', with PIM sparse-mode enabled on all interfaces and sink RP

The spare Gigabit Ethernet port on each router is bridged with the active one (so a portable management PC (laptop) can be plugged in there and communicate with the router and the industriual PC.

One host (industrial PC - core 2 due running Win XP Pro) connected to each router. Using a small network (WAN) with three 1921 routers (IOS 15.1(T)) connected via E1 links.

Wireshark portable no interfaces