📄 igrptheory.htm
字号:
<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 6.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>IGRP Overview</title>
</head>
<body>
<script language="Javascript">
<!--
function printpage() {
if (window.print)
window.print()
else
alert("Sorry, your browser doesn't support this feature.");
}
//-->
</script>
<FORM>
<INPUT TYPE="button" VALUE="Print this page" onClick="printpage()">
</FORM>
<p><b><font face="Arial, Helvetica" size="4" color="#008000">IGRP Overview</font></b></p>
<p><font face="Arial">Interior Gateway Routing Protocol (IGRP) is a standards-based, distance-vector,
interior gateway protocol (IGP) used by routers to exchange routing
information. IGRP uses a composite metric of bandwidth and delay to determine the best path between two
locations. The metric can also be administratively configured to factor in
the Maximum Transmission Unit (MTU), Reliability, and load for the link. In a
IGRP network, each router
broadcasts its entire IGRP table to its neighboring routers every 90 seconds. When a router receives a neighbor's
IGRP table, it uses the
information provided to update its own routing table and then sends the updated
table to its neighbors. This procedure is repeated by each router and results in
a state referred to as network convergence, in which all routers have an
identical view of the internetwork topology.</font></p>
<p><font face="Arial">IP Addresses: Please set these IP addresses on the interfaces of your routers.</font></p>
<table border="0" width="100%" height="53">
<tr>
<td width="20%" height="18" bgcolor="#00FF00"></td>
<td width="32%" height="18" bgcolor="#00FF00">eRouter1</td>
<td width="23%" height="18" bgcolor="#00FF00">eRouter2</td>
<td width="25%" height="18" bgcolor="#00FF00">eRouter4</td>
</tr>
<tr>
<td width="20%" height="8" bgcolor="#00FFFF">Interface<br>
Ethernet 0</td>
<td width="32%" height="8" bgcolor="#00FFFF">10.1.1.1<br>
255.255.255.0</td>
<td width="23%" height="8" bgcolor="#00FFFF">10.1.1.2<br>
255.255.255.0</td>
<td width="25%" height="8" bgcolor="#00FFFF"> </td>
</tr>
<tr>
<td width="20%" height="15" bgcolor="#00FFFF">Interface<br>
Serial 0</td>
<td width="32%" height="15" bgcolor="#00FFFF">172.16.10.1<br>
255.255.255.0</td>
<td width="23%" height="15" bgcolor="#00FFFF"> </td>
<td width="25%" height="15" bgcolor="#00FFFF">172.16.10.2 <br>
255.255.255.0</td>
</tr>
</table>
<p> </p>
<p><font face="Arial">Lets connect to eRouter1 and get it configured. We will be using the
table above for our IP addresses.</font><font color="#FF0000" face="Courier"><br>
<br>
</font><font face="Terminal" size="2">eRouter>en<br>
eRouter#conf t<br>
Enter configuration commands, one per line. End with CNTL/Z.<br>
eRouter(config)#int e0<br>
eRouter(config-if)#ip address 10.1.1.1 255.255.255.0<br>
eRouter(config-if)#no shut<br>
eRouter(config-if)#exit<br>
00:35:15: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up<br>
eRouter(config)#hostname eRouter1<br>
eRouter1(config)#int s0<br>
eRouter1(config-if)#ip address 172.16.10.1 255.255.0.0<br>
eRouter1(config-if)#no shut<br>
00:35:16: %LINK-3-UPDOWN: Interface Serial0, changed state to up<br>
eRouter1(config-if)#exit<br>
00:35:16: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up</font><font face="Times New Roman"><br>
</font>
</p>
<p> </p>
<p><font face="Arial">IGRP is classful, meaning it does not include the subnet mask in its
routing table updates. So now lets go ahead and start the lab.</font></p>
<p><font face="Arial">1. We first want to configure eRouter1 for IGRP. To enable IGRP as the routing protocol we only need to type: </font>
<font face="Terminal" size="2">router
IGRP <i>AS</i></font><font face="Arial" color="#FF0000">. </font><font face="Arial"> The AS stands for a Autonomous System number. An
Autonomous System is defined as a network under a common administration with a
common routing policy. You will need to use the <b>SAME</b> autonomous system
number on every router that you would like to share its routing table
with. We can see this below in the router output. Notice the new mode
we have entered eRouter1(config-router)# that tells us we are configuring the
router. </font></p>
<p><font face="Terminal" size="2">
eRouter1(config)#router IGRP 100<br>
eRouter1(config-router)#</font></p>
<p><font face="Arial">Now that we have IGRP running on our Router we need to tell the router which
networks it is connected to. We do this by using the network statement.
What this means is every interface of our router that is directly connected to an
active network needs a network number. We will have some networks using the same ip addressing
schemes with different subnets, and some are using entirely different addressing
schemes. Look at the diagram below. In this diagram we have three
different kinds of addressing schemes. Lets look at these in more
detail. On eRouter 1 we have an IP address of 10.1.1.1 with a /24 subnet
mask. Since IGRP is classful you are only required to enter the class part
of the address for the network statement. For example on eRouter1 we have
already issued the command router IGRP, we then need to specify the directly
connected networks to eRouter1 so the router can advertise these routes in its routing table. To do this we would only need to type: </font>
<font face="Terminal" size="2">network
10.0.0.0</font><font face="Arial">.<font color="#FF0000"> </font></font><font face="Arial">We have not told the router about the network on its serial interface, to do this we would type: </font>
<font face="Terminal" size="2">
network 172.16.0.0</font><font face="Arial">.<font color="#FF0000"> </font>Lets look at eRouter 2.
What network statement would we need to use on this router? ______________________________________(see
the answer below the diagram.) </font> </p>
<p> </p>
<p align="center"> <img border="0" src="default.jpg"></p>
<p><font face="Arial">The answer is </font>
<font face="Terminal" size="2">network 10.0.0.0</font><font face="Arial">.<font color="#FF0000"> </font></font><font face="Arial">The network statement for the
ethernet link is the same for eRouter1
and eRouter2. On eRouter1 what network statement would you need for the
serial link? For this network
statement you used the classful portion of the address 172.16.10.1 which would be
just </font><font face="Terminal" size="2">network 172.16.0.0</font><font face="Arial">.</font></p>
<p><font face="Arial">Now that we understand the network command lets enter it on our eRouter1.</font></p>
<p><font face="Courier" color="#FF0000"><br>
</font><font face="Terminal" size="2">eRouter1(config-router)#network 172.16.0.0<br>
eRouter1(config-router)#network 10.0.0.0<br>
eRouter1(config-router)#</font></p>
<p><font face="Arial">If you notice we only needed to enter 10.0.0.0 for our network statement, this is
because 10.0.0.0 is a Class A address and IGRP only uses the classful portion
of the address. Now we have configured eRouter1 for IGRP lets connect to
eRouter2 and get it setup.</font></p>
<p><font face="Arial"> We need to
connect to eRouter2 and follow the same instructions. Lets select eRouter2
from the Window pull down menu. When we connect we are going to set a hostname to eRouter2, then set the
IP addresses to the table above and configure
IGRP.</font> </p>
<p><font color="#FF0000" face="Courier"><br>
</font><font face="Terminal" size="2">eRouter>en<br>
eRouter#conf t<br>
Enter configuration commands, one per line. End with CNTL/Z.<br>
eRouter(config)#hostname eRouter2<br>
eRouter2(config)#int e0<br>
eRouter2(config-if)#ip address 10.1.1.2 255.255.255.0<br>
eRouter2(config-if)#no shut<br>
eRouter2(config-if)#exit<br>
01:23:17: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up<br>
01:23:18: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up<br>
eRouter2(config)#</font></p>
<p><font face="Arial">Now add the IGRP stuff!</font></p>
<p><font color="#FF0000" face="Courier"><br>
</font><font face="Terminal" size="2">eRouter2(config)#router IGRP 100<br>
eRouter2(config-router)#network 10.0.0.0<br>
eRouter2(config-router)#exit<br>
eRouter2(config)#exit<br>
eRouter2#</font></p>
<p>We should now have IGRP running on our network between eRouter1 and eRouter2.
We need to get eRouter4 setup.</p>
<p>We need to
connect to eRouter4 and follow the same instructions. Lets select eRouter4
from the Window pull down menu. When we connect we are going to set a hostname to
eRouter4, then set the ip addresses to the table above and configure IGRP. </p>
<p><font color="#FF0000" face="Courier"><br>
</font><font face="Terminal" size="2">eRouter>en<br>
eRouter#conf t<br>
Enter configuration commands, one per line. End with CNTL/Z.<br>
eRouter(config)#hostname eRouter4<br>
eRouter4(config)#int s0<br>
eRouter4(config-if)#ip address 172.16.10.2 255.255.0.0<br>
eRouter4(config-if)#no shut<br>
eRouter4(config-if)#exit<br>
01:23:17: %LINK-3-UPDOWN: Interface Ethernet0, changed state to up<br>
01:23:18: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up<br>
eRouter4(config)#</font></p>
<p><font face="Arial">Now add the IGRP stuff!</font></p>
<p><font face="Terminal" size="2">eRouter4(config)#router IGRP 100<br>
eRouter4(config-router)#network 172.16.0.0<br>
eRouter4(config-router)#exit<br>
eRouter4(config)#exit<br>
eRouter4#</font></p>
<p><font face="Arial"> Now that we have IGRP running on our entire network
lets verify that it is receiving routes. To do this we will be using some
show commands. The most common one is </font>
<font face="Terminal" size="2">show ip route</font><font face="Arial">. This displays all entries in the routing table. If we do
this on our eRouter 4 we will see the route to our directly connected eRouter1.
Lets take a look at our routing table, to do this type: </font>
<font face="Terminal" size="2">show
ip route</font><font face="Arial"> from the privilege mode.</font></p>
<p><font face="Arial">Lets look at the first entry </font>
<font face="Terminal" size="2">I 10.1.1.0/24
[100/273] via 172.16.10.1, 00:00:21, Serial0</font><font face="Arial">. It starts off saying it is an IGRP route, it then says the destination
network with subnet mask in this case is 10.1.1.0 with a /24 (255.255.255.0)
subnet mask. Next it gives 100/273 the 100 is the administrative distance, IGRP's default administrative distance is 100. Administrative distance is
considered the trustworthiness of the route. If you have two routing protocols
with the same route the router will pick the route with the lower number.
The 273 is the calculated metric, which is based on bandwidth delay. The next
piece of information is the via 172.16.10.1 that is the next hop address it must go
to. The last item is that this information was learned via
Serial0.</font> </p>
<p><font face="Arial">Another great command is<b> </b></font>
<font face="Terminal" size="2">show ip protocols</font><font face="Arial">. This displays information
about the ip routing protocols you have enabled. Lets type the command : </font>
<font face="Terminal" size="2">show ip protocols</font><font face="Arial"> and see what we get.</font></p>
<p><font face="Terminal" size="2">eRouter4#show ip protocols<br>
Routing Protocol is igrp 100<br>
Sending updates every 90 seconds, next due in 12 seconds<br>
Invalid after 270 seconds, hold down 280, flushed after 630<br>
Outgoing update filter list for all interfaces is not set<br>
Incoming update filter list for all interfaces is not set<br>
Default networks flagged in outgoing updates<br>
Default networks accepted from incoming updates<br>
IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0<br>
IGRP maximum hopcount 100<br>
IGRP maximum metric variance 1<br>
Redistributing: igrp 100<br>
Routing for Networks:<br>
172.16.0.0<br>
Routing Information Sources:<br>
Gateway Distance Last Update<br>
172.16.10.2 100 00:00:09<br>
Distance: (default is 100)<br>
<br>
eRouter4#</font></p>
<p><font face="Arial">Looking at the output in detail we see that we are sending updates every 90
seconds. We know IGRP is a distance vector routing protocol so it exchanges
its entire routing table every 90 seconds. We also see our network
statements are working by noticing the networks are both under the Routing for
Networks area. The last area to notice is the Distance which we said was
administrative distance. This tells us the default is 100 and that is what
we are using. </font> </p>
<p> </p>
<p><font face="Arial" size="2"><span class="724482219-24092001">Copyright (c)
1998-2003 Boson Software, Inc. All Rights Reserved.</span></font></p>
</body>
</html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -