Q1 - The network statement when used with RIP/RIPv2/IGRP/EIGRP/OSPF does not tell the router which networks to advertise. So
does not tell R1 to advertise 220.127.116.11. It tells R1 to start RIP running on any interface that falls into the 1.x.x.x range. So until you added the serial subnets RIP was not running on those interfaces and hence the routers were not exchanging routes.
As for the /8 networks did you disable auto-summarisation on your routers ie.
if you didn't then RIP will summarise across classful boundaries and because your serial links are 12.x.x.x and 13.x.x.x then the LAN subnets will be summarised to 18.104.22.168/8.
If I understood correctly what you mentioned, then the routers should have sent RIP updates on the fastethernet interface, but not on the serial interfaces. However I didn't see any RIP updates at all.
Is there an explanation for this?
Also, regarding Ping question, do you have any hint why it worked, whereas my common sense would have bet that it would never work?
"If I understood correctly what you mentioned, then the routers should have sent RIP updates on the fastethernet interface, but not on the serial interfaces. However I didn't see any RIP updates at all."
You should have seen something happening on the router. When i tested this by enabling RIP on just one interface on a router i was getting advertisement suppressed messages.
On your router
debug ip rip
and you should see messages. But if the advertisement is being suppressed you won't capture it with a packet sniffer on a PC.
"Also, regarding Ping question, do you have any hint why it worked, whereas my common sense would have bet that it would never work?"
R1 has 2 routes to the same destination so it will use both routes. This could cause a problem but if you draw out your topology you will see that in fact it doesn't matter whether R1 sends it to R2 or R3 because R2 & R3 are interconnected so the packet can just be forwarded between the two to get to the right destination.
In your scenario, for the routers to send/receive RIP updates to/from other routers the subnets of the serial interfaces need to be added to the RIP configuration, otherwise they won't advertise anything. If you only add the LAN subnet but you don't add the serial subnets then the LAN subnet won't be advertised because the serial interfaces are not in the RIP configuration and because of that they don't advertise.
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