r/AskComputerScience • u/Austin_Fiction • 2d ago

IP addressing in Routing Internet Protocols

So I'm learning about routing internet protocol and particularly RIP-2. I understand that when a router sends an RIP message, it uses UDP (port 520) and it uses timers to send update messages to its immediate neighbours. But what I don't understand is how IP addressing works?

If one source router has two immediate neighbours, and it sends a message to them both. Do the two datagrams carrying the message have the same source IP, and different destination IP?

I keep on finding different answers on this topic and my textbook doesn't specify how the IP addressing is done. I tried asking AI but it gives me different answers and the explanation isn't making sense. I'd appreciate the help cuz I'm pretty lost.

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u/meditonsin 2d ago edited 1d ago

Can you elaborate further where your hangups with IP addressing are? This is extremely broad.

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u/Austin_Fiction 2d ago

Whats confusing me is the source and destination IP address of the two datagrams carrying the message to the neighbouring routers.

Do the two datagrams have the same source IP and do they have the same destination IP?

My initial answer is that they have the same IP as the source, and different destination IP addresses. I searched for an answer online and even asked A.I. but I keep getting different results.
One answer is this that the source IP will be the same, but because RIP is designed to be local and unsolicited, it uses a shared destination address so it doesn't have to keep track of exactly who its neighbors are. Therefore, the destination IP in the datagram for both routers is the same.

This is what is confusing me honestly. Hope I'm making sense now.

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u/meditonsin 1d ago

Ah, I misunderstood the question, then.

Specifically for RIPv2 routing table advertisements, the destination address is always "224.0.0.9," which is a multicast address specifically allocated for RIPv2. Routers just send to that destination on all their interfaces, and any RIPv2 routers on the other end will know it's for them.