CCNA6-10

392 Chapter 6  IP Routing
RIPv2, unlike RIPv1, is a classless routing protocol (even though it is configured as classful,
like RIPv1), which means that it sends subnet mask information along with the route updates.
By sending the subnet mask information with the updates, RIPv2 can support Variable Length
Subnet Masks (VLSMs) as well as the summarization of network boundaries. In addition,
RIPv2 can support discontiguous networking, which I’ll go over more in Chapter 7.
Configuring RIPv2 is pretty straightforward. Here’s an example:
Lab_C(config)#router rip
Lab_C(config-router)#network 192.168.40.0
Lab_C(config-router)#network 192.168.50.0
Lab_C(config-router)#version 2
That’s it; just add the command version 2 under the (config-router)# prompt and you
are now running RIPv2.
RIPv2 is classless and works in VLSM and discontiguous networks.
Interior Gateway Routing Protocol (IGRP)
Interior Gateway Routing Protocol (IGRP) is a Cisco-proprietary distance-vector routing protocol.
This means that to use IGRP in your network, all your routers must be Cisco routers.
Cisco created this routing protocol to overcome the problems associated with RIP.
IGRP has a maximum hop count of 255 with the default being 100 (same as EIGRP). This
is helpful in larger networks and solves the problem of 15 hops being the maximum possible
in a RIP network.
IGRP also uses a different metric than RIP. IGRP uses bandwidth and delay of the line by
default as a metric for determining the best route to an internetwork. This is called a composite
metric. Reliability, load, and maximum transmission unit (MTU) can also be used, although
they are not used by default.
The main difference between RIP and IGRP configuration is that when you
configure IGRP, you supply the autonomous system number. All routers
must use the same number in order to share routing table information.
Table 6.4 shows a list of IGRP characteristics that you won’t find in RIP.
Verifying Your Configurations 393
Why is this the end of the IGRP section? Because watch what happens when I try to configure
IGRP on my router:
R3#config t
Enter configuration commands, one per line. End with CNTL/Z.
R3(config)#router igrp 10
^
% Invalid input detected at '^' marker.
R3(config)#
There’s your reason—Cisco no longer supports IGRP. Why should it? All you have to do is
put an E in front of IGRP and you’re running a much, much better routing protocol. We’ll get
to EIGRP in the next chapter, but first, let’s go through some verification commands for RIP.
Verifying Your Configurations
It’s important to verify your configurations once you’ve completed them, or at least once you
think you’ve completed them. The following list includes the commands you can use to verify
the routed and routing protocols configured on your Cisco routers:
 show ip route
 show ip protocols
 debug ip rip
The first command was covered in the previous section—I’ll go over the others in the
sections that follow.
TABLE 6 . 4 IGRP vs. RIP
IGRP RIP
Can be used in large internetworks Works best in smaller networks
Uses an autonomous system number for
activation
Does not use autonomous system
numbers
Gives a full route table update every 90 seconds Gives a full route table update every
30 seconds
Has an administrative distance of 100 Has an administrative distance of 120
Uses bandwidth and delay of the line as metric
(lowest composite metric), with a maximum hop
count of 255
Uses only hop count to determine the best
path to a remote network, with 15 hops
being the maximum
394 Chapter 6  IP Routing
The show ip protocols Command
The show ip protocols command shows you the routing protocols that are configured on
your router. Looking at the following output, you can see that RIP is running on the router and
the timers that RIP uses:
R3#sh ip protocols
Routing Protocol is "rip"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Sending updates every 30 seconds, next due in 24 seconds
Invalid after 180 seconds, hold down 180, flushed after 240
Redistributing: rip
Default version control: send version 1, receive version 1
Interface Send Recv Triggered RIP Key-chain
FastEthernet0/1 1 1
Serial0/0/1 1 1
Automatic network summarization is not in effect
Maximum path: 4
Routing for Networks:
10.0.0.0
Passive Interface(s):
FastEthernet0/0
Serial0/0/0
Routing Information Sources:
Gateway Distance Last Update
10.1.11.2 120 00:00:10
10.1.5.1 120 00:00:22
Distance: (default is 120)
Notice in this output that RIP is sending updates every 30 seconds, which is the default. The
timers used in distance vector are also shown.
Notice further down that RIP is routing for directly connected interfaces f0/1 and s0/0/0.
The version is listed to the right of the interfaces—RIPv1.
F0/0 and s0/0/0 are listed as passive interfaces (they will not send RIP information out). The
neighbors it found are 10.1.11.2 and 10.1.5.1. The last entry is the default AD for RIP (120).
Troubleshooting with the show ip protocols Command
Let’s use a sample router and use the show ip protocols command to see what we can determine
about routing by looking at this output from a router on another network:
Router#sh ip protocols
Routing Protocol is "rip"
Verifying Your Configurations 395
Sending updates every 30 seconds, next due in 6 seconds
Invalid after 180 seconds, hold down 180, flushed after240
Outgoing update filter list for all interfaces is
Incoming update filter list for all interfaces is
Redistributing: rip
Default version control: send version 1, receive any version
Interface Send Recv Key-chain
Serial0/0 1 1 2
Serial0/1 1 1 2
Routing for Networks:
10.0.0.0
Routing Information Sources:
Gateway Distance Last Update
10.168.11.14 120 00:00:21
Distance: (default is 120)
Let’s also look at the show ip interface brief command from the same router and see
what we find out:
Router#sh ip interface brief
Interface IP-Address OK? Method Status
FastEthernet0/0 192.168.18.1 YES manual up
Serial0/0 10.168.11.17 YES manual up
FastEthernet0/1 unassigned YES NRAM Administatively down
Serial0/1 192.168.11.21 YES manual up
Under the show ip protocols output, you can see that we’re using RIP routing for network
10.0.0.0, which means our configuration would look like this:
Router(config)#router rip
Router(config-router)#network 10.0.0.0
Also, only serial 0/0 and serial 0/1 are participating in the RIP network. And last, our neighbor
router is 10.168.11.14.
From the output of the show ip interface brief command, you can see that only serial
0/0 is in the 10.0.0.0 network. This means that the router will only send and receive routing
updates with the 10.0.0.0 network and not advertise the 192.168.0.0 networks out any interface.
The debug ip rip Command
The debug ip rip command sends routing updates as they are sent and received on the router
to the console session. If you are telnetted into the router, you’ll need to use the terminal
monitor command to be able to receive the output from the debug commands.
396 Chapter 6  IP Routing
We can see in this output that RIP is both sending and receiving (the metric is the hop count):
R3#debug ip rip
RIP protocol debugging is on
R3#terminal monitor
*Mar 17 19:08:34.371: RIP: sending v1 update to 255.255.255.255 via
Serial0/0/1 (10.1.5.2)
*Mar 17 19:08:34.371: RIP: build update entries
*Mar 17 19:08:34.371: subnet 10.1.10.0 metric 1
*Mar 17 19:08:34.371: subnet 10.1.11.0 metric 1
*Mar 17 19:08:34.371: subnet 10.1.12.0 metric 2
*Mar 17 19:08:40.107: RIP: received v1 update from 10.1.5.1 on
Serial0/0/1
*Mar 17 19:08:40.107: 10.1.1.0 in 1 hops
*Mar 17 19:08:40.107: 10.1.2.0 in 1 hops
*Mar 17 19:08:40.107: 10.1.3.0 in 1 hops
*Mar 17 19:08:40.107: 10.1.4.0 in 1 hops
*Mar 17 19:08:40.107: 10.1.6.0 in 2 hops
*Mar 17 19:08:40.107: 10.1.7.0 in 2 hops
*Mar 17 19:08:40.107: 10.1.8.0 in 2 hops
*Mar 17 19:08:40.107: 10.1.9.0 in 2 hops
*Mar 17 19:08:47.535: RIP: sending v1 update to 255.255.255.255 via
FastEthernet0/1 (10.1.11.1)
*Mar 17 19:08:47.535: RIP: build update entries
*Mar 17 19:08:47.535: subnet 10.1.1.0 metric 2
*Mar 17 19:08:47.535: subnet 10.1.2.0 metric 2
*Mar 17 19:08:47.535: subnet 10.1.3.0 metric 2
*Mar 17 19:08:47.535: subnet 10.1.4.0 metric 2
*Mar 17 19:08:47.535: subnet 10.1.5.0 metric 1
*Mar 17 19:08:47.535: subnet 10.1.6.0 metric 3
*Mar 17 19:08:47.535: subnet 10.1.7.0 metric 3
*Mar 17 19:08:47.535: subnet 10.1.8.0 metric 3
*Mar 17 19:08:47.535: subnet 10.1.9.0 metric 3
*Mar 17 19:08:47.535: subnet 10.1.10.0 metric 1
*Mar 17 19:08:49.331: RIP: received v1 update from 10.1.11.2 on
FastEthernet0/1
*Mar 17 19:08:49.331: 10.1.12.0 in 1 hops
R3#undeug all
*Mar 17 19:08:47.535: subnet 10.1.10.0 metric 1
*Mar 17 19:08:49.331: RIP: received v1 update from 10.1.11.2 on
FastEthernet0/1