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The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employ the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from source to destination. The largest number of hops allowed for RIP is 15, which limits the size of networks that RIP can support.
RIP implements the split horizon, route poisoning and holddown mechanisms to prevent incorrect routing information from being propagated.
In RIPv1 router broadcast updates with their routing table every 30 seconds. In the early deployments, routing tables were small enough that the traffic was not significant. As networks grew in size, however, it became evident there could be a massive traffic burst every 30 seconds, even if the routers had been initialized at random times.
In most networking environments, RIP is not the preferred choice for routing as its time to converge and scalability are poor compared to EIGRP, OSPF, or IS-IS. However, it is easy to configure, because RIP does not require any parameters unlike other protocols.
RIP uses the User Datagram Protocol (UDP) as its transport protocol, and is assigned the reserved port number 520
Based on the Bellman–Ford algorithm and the Ford–Fulkerson algorithm distant-vector routing protocols started to be implemented from 1969 onwards in data networks such as the ARPANET and CYCLADES. The predecessor of RIP was the Gateway Information Protocol (GWINFO) which was developed by Xerox in the mid-1970s to route its experimental network. As part of the Xerox Network Systems (XNS) protocol suite GWINFO transformed into the XNS Routing Information Protocol. This XNS RIP in turn became the basis for early routing protocols, such as Novell’s IPX RIP, AppleTalk’s Routing Table Maintenance Protocol (RTMP), and the IP RIP. The 1982 Berkley Software Distribution of the UNIX operating system implemented RIP in the routed daemon. The 4.2BSD release proved popular and became the basis for subsequent UNIX versions, which implemented RIP in the routed or gated daemon. Ultimately RIP had been extensively deployed before the standard written by Charles Hedrick was passed as RIPv1 in 1988.
Transcription:
So on the Internet router; we can do some additional tests if we want to.
We can ping the loopback of router 1, router 2, router 3 and ourselves.
Notice we have a gateway of last resort. We have a default route pointing to the Internet. So we should be able to ping 8.8.8.8 which is the DNS server. We should be able to ping Cisco.com. Notice that’s resolved and the ping succeeds. And we should be able to ping Facebook.com.
So the Internet router has received an IP address through DHCP. It’s also learned a default route as we can see here. It has a gateway of last resort and it’s been told via DHCP which DNS server to use, which is this server here.
Notice the DNS records for Cisco and Facebook and here’s the DHCP server telling devices the default gateway, DNS server and we have an address pool configured.
So that router can get to the Internet but a router such as router 1, won’t be able to get to the Internet because this router only knows about the internal networks. So it knows about network 1 and network 10. It doesn’t have a gateway of last resort set. It doesn’t have a default route. So it won’t be able to ping the DNS server, as an example, because it doesn’t know where network 8 is. We have to advertise a default route to the router and we’re going to do that on the Internet router.
So router rip
we use this command default-information originate
to advertise a default route through RIP.
So notice previously, there was no default route, no gateway of last resort set.
show ip route
now, however, shows us that a gateway of last resort is configured and we have a default route learned via RIP. Notice it’s a candidate default route learned via RIP, our gateway is the Internet router.
So Internet router once again
show ip interface brief
has this IP address configured on the serial link to router 1. So router 1 should be able to ping the DNS server which it can, and it should be able to ping Cisco.com but we have to configure a name server for that.
So let’s configure the name server and see if we can ping Cisco.com. Yes, we can.
Can we ping Facebook.com? Yes we can….
