I had some requests for the final configs so I have fixed those. You can download them here. Also I had some issues getting the traffic through but thanks to my helpful readers like zumzum I now have it figured out.

Lets start on R4 since this is the source of the traffic.

R4 wants to send traffic to 1.1.1.1 with a source of 155.1.12.4. We know that route via RIP and the next-hop is 155.1.12.1. That network is directly connected (secondary). We need to find out the MAC address of 155.1.12.1 for our ARP entry. R3 has proxy arp enabled, which is the default. However it will not respond to R4 ARP request since it does not have the subnet 155.1.12.0/24 connected. R4 must therefore have a static ARP entry. I did an error here earlier by typing in R1 MAC but this should be the MAC of R3 Fa0/0 since that is the link connecting us. We create the static ARP with arp 155.1.12.1 xxxx.xxxx.xxxx arpa. R4 now has all the info needed.

Packet travels to R3. R3 does not have a route for 1.1.1.1. We create a static route, ip route 1.1.1.0 255.255.255.0 155.1.23.2. We also need a static route back to R4 for the 155.1.12.4 IP. Ip route 155.1.12.4 255.255.255.0 155.1.34.4.

Packet now travels to R2. R2 also needs to know about 1.1.1.1 so we add a route there as well. Ip route 1.1.1.0 255.255.255.0 155.1.12.1. R2 also needs to find its way back to R4 so we add a static route, ip route 155.1.12.4 255.255.255.255 155.1.23.2.

Packet goes to R1 which will respond. It will send the packet out Fa0/0. R1 needs to know the MAC address for 155.1.12.4. R2 has proxy ARP enabled so it will reply with its own MAC address to R1. R1 will insert this into ARP cache and adjacency table and then we are good to go.

So except learning a multicast feature we also got to practice how to make connectivitiy in an unusual way and think through the whole process of packet flow.

Followup on multicast helper map
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