Example 11-1 Router Routing Table

   

Lab Objectives

Before beginning, review the lab objectives and the routing domains in the network. This will help you understand where route redistribution needs to occur.

  • On R2, redistribute RIP into EIGRP and redistribute EIGRP into RIP.

  • On R3, redistribute EIGRP into IGRP and redistribute IGRP into EIGRP.

  • Fix any routing problems that you encounter as you see fit.

All routers should be capable of ping ing all interfaces at the end of this section.

Figure 11-1 outlines the routing domains.

Figure 11-1. Routing Domains

graphics/11fig01.gif

Before beginning with the route redistribution configuration, take a look at each of the router's routing table to see how it appears now and how it will change after redistributing the routes. Example 11-1 depicts the routing tables for the routers thus far.

 R1#  show ip route  Gateway of last resort is not set C    192.169.1.0/24 is directly connected, Loopback0 C    192.168.1.0/24 is directly connected, Ethernet0 R    192.168.2.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.169.2.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 _______________________________________________________________________ R2#  show ip route  Gateway of last resort is not set      192.168.4.0/27 is subnetted, 1 subnets D       192.168.4.0 [90/2707456] via 192.168.100.3, 1d03h, Serial0 C    192.168.1.0/24 is directly connected, Ethernet0 R    192.169.1.0/24 [120/1] via 192.168.1.1, 00:00:02, Ethernet0 C    192.168.2.0/24 is directly connected, Ethernet1 C    192.169.2.0/24 is directly connected, Loopback0 C    192.168.100.0/24 is directly connected, Serial0 D    192.168.3.0/24 [90/2195456] via 192.168.100.3, 2d03h, Serial0 D    200.200.0.0/16 [90/2809856] via 192.168.100.3, 1d03h, Serial0 _______________________________________________________________________ R3#  show ip route  Gateway of last resort is not set C    192.168.100.0/24 is directly connected, Serial0 C    192.168.35.0/24 is directly connected, Serial1 I    192.168.50.0/24 [100/8539] via 192.168.35.5, 00:01:02, Serial1 C    192.169.3.0/24 is directly connected, Loopback0 C    192.168.3.0/24 is directly connected, Ethernet0      192.168.4.0/27 is subnetted, 1 subnets D       192.168.4.0 [90/2195456] via 192.168.100.4, 1d03h, Serial0 D    192.169.4.0/24 [90/2297856] via 192.168.100.4, 00:06:19, Serial0 I    192.169.5.0/24 [100/8976] via 192.168.35.5, 00:01:02, Serial1 D    200.200.0.0/16 [90/2297856] via 192.168.100.4, 1d03h, Serial0 _______________________________________________________________________ R4#  show ip route  Gateway of last resort is not set C    200.200.1.0/24 is directly connected, Loopback1 C    200.200.2.0/24 is directly connected, Loopback2 C    192.168.100.0/24 is directly connected, Serial0 D    192.168.3.0/24 [90/2195456] via 192.168.100.3, 1d03h, Serial0      192.168.4.0/27 is subnetted, 1 subnets C       192.168.4.0 is directly connected, Ethernet0 C    192.169.4.0/24 is directly connected, Loopback0 D    200.200.0.0/16 is a summary, 1d03h, Null0 _______________________________________________________________________ R5#  show ip route  Gateway of last resort is not set C    192.168.35.0/24 is directly connected, Serial0 C    192.168.50.0/24 is directly connected, TokenRing0 I    192.169.3.0/24 [100/8976] via 192.168.35.3, 00:00:45, Serial0 C    192.169.5.0/24 is directly connected, Loopback0 

Example 11-1 shows that each of the router's routing tables are fairly small and include only the routes pertaining to the routing protocol that each is using. When you have completed this chapter, you should see several more routes and should be able to ping every interface on every router, except R6. R6 is unreachable at this time because it will be connected to the network using dial-on-demand routing (DDR) in Chapter 12, "Integrated Services Digital Network (ISDN)."

Redistributing Between RIP and EIGRP

As you can see, R2 is the boundary for RIP, and EIGRP and R3 is the boundary for EIGRP and IGRP. It is at these two " crossroads " that you will redistribute routes between the routing protocols.

The first lab objective is to redistribute between RIP and EIGRP. To redistribute routes from one protocol to another, you need to issue the redistribute command under the routing protocol in which you want to introduce the routes from the other routing protocol. The command syntax to accomplish this is as follows :

 Router(config-router)#  redistribute   protocol autonomous-system-number metric  [  route-map   map-ta  g] 

You need to concern yourself only with the first three parameters of the command. For the protocol parameter of the command, you need to supply the routing protocol from which you want to redistribute routes. The autonomous-system parameter pertains only to those routing protocols that use autonomous system number identifiers. With the metric parameter you manually specify the metrics for the routes being introduced into the routing protocol.

Begin by configuring route redistribution on R2. Redistribute EIGRP routes into RIP and then RIP routes into EIGRP. Example 11-2 demonstrates the command for redistributing EIGRP routes into RIP.

Example 11-2 Route Redistribution for RIP on R2
 Termserver#  2  [Resuming connection 2 to r2 ... ] R2# R2#  config t  Enter configuration commands, one per line. End with CNTL/Z. R2(config)#  router rip  R2(config-router)#  redistribute eigrp 100    metric 1   R2(config-router)# 

Because RIP uses hop counts, you can set all routes coming from EIGRP as one hop away. As you know, most of these routes are not one hop away, but for RIP to be capable of placing them into the routing table, one hop count is the minimum that you can specify. It is important to review your routing environment before arbitrarily assigning metrics. Because of the simplicity of the lab topology, the metric assignment is not critical, but in a production environment, it is very critical to review metrics because they control the paths selected for your network traffic. Example 11-3 provides the configuration to now redistribute RIP routes into EIGRP AS 100.

Example 11-3 Redistributing RIP into EIGRP on R2
 R2(config-router)  #exit  R2(config)#  router eigrp 100  R2(config-router)#  redistribute rip metric ?   <1-4294967295>  Bandwidth metric in Kbits per second  R2(config-router)#  redistribute rip metric 2000 ?   <0-4294967295>  IGRP delay metric, in 10 microsecond units  R2(config-router)#  redistribute rip metric 2000 200 ?   <0-255>  IGRP reliability metric where 255 is 100% reliable  R2(config-router)#  redistribute rip metric 2000 200 255 ?   <1-255>  IGRP Effective bandwidth metric (Loading) where 255 is 100% loaded  R2(config-router)#  redistribute rip metric 2000 200 255 1 ?   <1-4294967295>  IGRP MTU of the path  R2(config-router)#  redistribute rip metric 2000 200 255 1 1500  R2(config-router)# 

Because EIGRP uses a more complex metric calculation for path selection, Example 11-3 employed the CLI inline help functionality to help you understand the metric sequence and available values.

The first metric option is bandwidth. Example 11-3 uses a standard 2000-bandwidth metric, but this will change according to the media to which you are attached.

The second metric is delay. Usually this is in direct correlation to the bandwidth. Example 11-3 uses a 200-microsecond delay value for this lab.

The third metric is reliability. Consider the links to be 100 percent reliable, thus equating to a 255 value (255 being 100 percent reliable).

The fourth metric is load. Consider all links to have minimum traffic. 255 is a fully loaded circuit, and 1 is not.

The fifth metric is MTU size. The standard MTU size for Ethernet is 1500, so this will be the default here.

Remember, these values can drastically change the way a real production network will route, so be very thoughtful and thorough before issuing the redistribute command.

After redistributing between RIP and EIGRP, you should see some changes. R2 will not show any changes because it is running both protocols, but R1, R3, and R4 should be very different. Go to R1 and take a look at the routing table as demonstrated in Example 11-4.

Example 11-4 R1's Routing Table
 Termserver#  1  [Resuming connection 1 to r1 ... ] R1#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2        E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set  R    192.168.100.0/24 [120/1] via 192.168.1.2, 00:00:11, Ethernet0  C    192.169.1.0/24 is directly connected, Loopback0 C    192.168.1.0/24 is directly connected, Ethernet0 R    192.168.2.0/24 [120/1] via 192.168.1.2, 00:00:12, Ethernet0  R    192.168.3.0/24 [120/1] via 192.168.1.2, 00:00:12, Ethernet0  R    192.169.2.0/24 [120/1] via 192.168.1.2, 00:00:12, Ethernet0  R    192.168.4.0/24 [120/1] via 192.168.1.2, 00:00:12, Ethernet0   R    192.169.4.0/24 [120/1] via 192.168.1.2, 00:00:12, Ethernet0  

The highlighted portion in Example 11-4 illustrates the changes in the routing table, among which are several additions:

 R    192.168.100.0/24 [120/1] via 192.168.1.2, 00:00:11, Ethernet0 

This route is the Frame Relay network.

 R    192.168.3.0/24 [120/1] via 192.168.1.2, 00:00:12, Ethernet0 

This route is to R3's Ethernet 0 network.

 R    192.169.4.0  /24  [120/1] via 192.168.1.2, 00:00:12, Ethernet0 

This route is R4's loopback 0 network.

 R    192.168.4.0/  24  [120/1] via 192.168.1.2, 00:00:12, Ethernet0 

This route is to R4's Ethernet 0 network.

It is interesting to note that the subnet mask on R4's Ethernet 0 is a /27 bit mask, but the route on R1 is a /24 bit mask. This is because EIGRP will autosummarize the route to its classful boundary, 192.168.4.0 /24. It is important to understand this because RIP, being a classful routing protocol, would not understand a route with a /27 bit mask and would drop the route. Remember that RIP and IGRP do not send subnet mask information with their routing updates.

If a router running RIP or IGRP receives a route, such as a Class B or Class A address space, it checks to see if it has an interface configured in the same address space. If it does, it assumes that the same subnet mask on its interface is being used through the network and, by default, applies the subnet mask of its interface to the route that it received. If it does not have an interface configured in the same address space, it applies the classful subnet mask according to the route that it received. For example, if a router has an interface configured with an IP address of 172.16.2.1 /24, and it receives a route in the 172.16.5.0 address space, it applies the /24 mask to the route and the route looks like 172.16.5.0/24. If it does not have an interface configured in the 17.16.0.0 address space, it applies the default /16 bit mask (172.X.X.X being a Class B address) to the route; the route would be 172.16.0.0/16, pointing to the next hop that it learned through the routing update.

Notice that the two loopback interfaces configured on R4 and summarized to 200.200.0.0/16 are omitted from the routing table. Again, RIP and IGRP are classful routing protocols, meaning that they do not support VLSM or CIDR routing updates. The summary route to 200.200.0.0 is a Class C (200.X.X.X) address space being summarized to a Class B subnet mask (/16). This is known as classless interdomain routing (CIDR), although many network engineers refer to this as supernetting or route summarizing. CIDR is the act of sum-marizing several routes under one route. Earlier, the two loopback networks (200.200.1.0/24 and 200.200.2.0/24) were summarized into one route, 200.200.0.0/16, on R4. EIGRP understands this concept, but RIP and IGRP do not, so they disregard the route when EIGRP tries to redistribute it into RIP.

To ping the two loopback networks, you need to manually specify the route. You have three options:

  • Set a default route.

  • Set a default network.

  • Set static routes to the individual networks.

You will encounter this same issue for IGRP, so use one solution here and another for IGRP. Resolve this issue on R1 by setting a default route.

In global configuration mode, the command for setting a default route is as follows:

 Router(config)#  ip route 0.0.0.0 0.0.0.0   next-hop-address [metric]  

The next-hop-address parameter of this command is the IP address of the default gateway. This IP address must be a directly connected neighbor.

The metric parameter is the administrative distance of the route. For purposes here, do not change the default administrative distance for a static route (which is 1).

NOTE

Administrative distance is the first criterion that a router uses to determine which routing protocol to use if two protocols provide route information for the same destination. Table 11-1 shows the administrative distances for all routing protocols.


Table 11-1. Administrative Distances by Routing Protocol
Route Source Default Distance Values
Connected interface
Static route 1
Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5
External Border Gateway Protocol (BGP) 20
Internal EIGRP 90
IGRP 100
OSPF 110
Intermediate System-to-Intermediate System (IS-IS) 115
Routing Information Protocol (RIP) 120
Exterior Gateway Protocol (EGP) 140
External EIGRP 170
Internal BGP 200
Unknown 255

With R1 having only one other router connected to it, you need to use the Ethernet IP address of R2 as the default gateway. Example 11-5 illustrates the command on R1.

Example 11-5 Configuring Default Route on R1
 R1#  config t  Enter configuration commands, one per line. End with CNTL/Z.  R1(config)#  ip route 0.0.0.0 0.0.0.0 192.168.1.2  R1(config)# 

Next, look at R1's routing table in Example 11-6 to see how the default route appears in the table.

Example 11-6 R1's IP Routing Table
 R1#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2        E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR  Gateway of last resort is 192.168.1.2 to network 0.0.0.0  R    192.168.100.0/24 [120/1] via 192.168.1.2, 00:00:09, Ethernet0 C    192.169.1.0/24 is directly connected, Loopback0 C    192.168.1.0/24 is directly connected, Ethernet0 R    192.168.2.0/24 [120/1] via 192.168.1.2, 00:00:09, Ethernet0 R    192.168.3.0/24 [120/1] via 192.168.1.2, 00:00:09, Ethernet0 R    192.169.2.0/24 [120/1] via 192.168.1.2, 00:00:09, Ethernet0 R    192.168.4.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.169.4.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 S*   0.0.0.0/0 [1/0] via 192.168.1.2 R1# 

The routing table now informs you in two ways of the default route. The first is highlighted in Example 11-6:

 Gateway of last resort is 192.168.1.2 to network 0.0.0.0. 

The second way is to display the default route as a static route:

 S*   0.0.0.0/0 [1/0] via 192.168.1.2 

It is important to note that default routes are considered static routes, denoted by the S. However, to distinguish a default route from a regular static route a * is placed after the S.

Now that R1 has a default route, you should be able to ping all interfaces from R1 that were learned through EIGRP. For brevity in the lab, you need only ping a few interfaces, but in a live environment, you should take the time to ping all the EIGRP interfaces from R1 and then ping all the RIP interfaces from R3 or R4.

Example 11-7 displays several ping results from R1 to R4's loopback 0 and loopback 1, and R3's Serial 0 and Ethernet 0.

Example 11-7 ping Results from R1 to R4 and R3
 R1#  ping 192.169.4.4  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.169.4.4, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 88/90/92 ms R1#  ping 200.200.1.4  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 200.200.1.8, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 88/89/92 ms R1#  ping 200.200.2.4  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 200.200.2.8, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 88/90/96 ms R1#  ping 192.168.100.3  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.100.3, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 32/33/36 ms R1#  ping 192.168.3.3  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.3.3, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 32/34/36 ms R1# 

The ping output indicates 100 percent success on all ping ed networks.

To verify that RIP is properly redistributed into EIGRP, go to R4 and take a look at its routing table in Example 11-8.

Example 11-8 R4's IP Routing Table
 Termserver#  4  [Resuming connection 4 to r4 ... ] R4#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2        E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set C    200.200.1.0/24 is directly connected, Loopback1 C    200.200.2.0/24 is directly connected, Loopback2 C    192.168.100.0/24 is directly connected, Serial0  D EX 192.169.1.0/24 [170/2733056] via 192.168.100.3, 01:23:47, Serial0   D EX 192.168.1.0/24 [170/2733056] via 192.168.100.3, 02:13:53, Serial0   D EX 192.168.2.0/24 [170/2733056] via 192.168.100.3, 02:13:53, Serial0   D EX 192.169.2.0/24 [170/2733056] via 192.168.100.3, 02:13:53, Serial0  D    192.168.3.0/24 [90/2195456] via 192.168.100.3, 1d06h, Serial0      192.168.4.0/27 is subnetted, 1 subnets C       192.168.4.0 is directly connected, Ethernet0 C    192.169.4.0/24 is directly connected, Loopback0 D    200.200.0.0/16 is a summary, 1d06h, Null0 

EIGRP makes it a little easier to determine which routes were redistributed. It denotes routes learned external to EIGRP with an "EX" symbol after the D. Take a look at the new routes individually:

 D EX 192.169.1.0/24 [170/2733056] via 192.168.100.3, 01:23:47, Serial0 

This route is to R1's loopback 0 network.

 D EX 192.168.1.0/24 [170/2733056] via 192.168.100.3, 02:13:53, Serial0 

This route is to R1 and R2's Ethernet 0 network.

 D EX 192.168.2.0/24 [170/2733056] via 192.168.100.3, 02:13:53, Serial0 

This route is to R2's Ethernet 1 network.

 D EX 192.169.2.0/24 [170/2733056] via 192.168.100.3, 02:13:53, Serial0 

This route is R2's loopback 0 network.

Before moving on to redistribute EIGRP and IGRP, ping R1's loopback 0 and R1's Ethernet 0 interfaces, just to verify IP connectivity, as done in Example 11-9.

Example 11-9 R4 ping Results to R1
 R4#  ping 192.169.1.1  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.169.1.1, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 88/92/104 ms R4#  ping 192.168.1.1  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 88/89/92 ms 

RIP and EIGRP are redistributing correctly, and the default route statement is working properly on R1. Next, look at R1 and R2's configuration to understand how the commands that you entered appear in the configuration file. Example 11-10 depicts the output from the running config file on R1.

Example 11-10 Portion of R1's Running Config
 R1#  show running-config  . . ! router rip  network 192.168.1.0  network 192.169.1.0 ! no ip classless  ip route 0.0.0.0 0.0.0.0 192.168.1.2  ! banner motd ^C This is Router 1 ^C . 

All static and default routes appear in the configuration file after the routing protocols. Actual redistribution commands appear under the routing protocol. Example 11-11 illustrates a portion of R2's configuration file.

Example 11-11 Portion of R2's Running Config File
 R2#  show running-config  . . ! router eigrp 100  redistribute rip metric 2000 200 255 1 1500  network 192.168.100.0 ! router rip  redistribute eigrp 100 metric 1  network 192.168.1.0  network 192.168.2.0  network 192.169.2.0 ! . . 

When redistributing, the source protocol is redistributed into the destination protocol. You accomplish this by entering router configuration mode for the destination protocol and then using the redistribute command to bring in the source protocol's routes. All of the configuration files look good. In the next section, you will redistribute IGRP and EIGRP on R3.

Redistributing Between IGRP and EIGRP

With the boundaries for EIGRP and IGRP meeting at R3, R3 is the place where you need to configure route redistribution. In this section, you will redistribute EIGRP into IGRP and then IGRP into EIGRP. The command syntax is the same here as it was on R2. Use the same values that you used for EIGRP on R2 for both routing protocols. Example 11-12 illustrates the configuration for redistributing EIGRP into IGRP on R3.

Example 11-12 Redistributing EIGRP into IGRP on R3
 Termserver#  3  [Resuming connection 3 to r3 ... ] R3#  config t  Enter configuration commands, one per line. End with CNTL/Z. R3(config)#  router igrp 200  R3(config-router)#  redistribute eigrp 100 metric 2000 200 255 1 1500  R3(config-router)# 

Now redistribute IGRP routes into EIGRP using the configuration for R3 in Example 11-13.

Example 11-13 Redistributing IGRP into EIGRP on R3
 R3(config-router)#  exit  R3(config)#  router eigrp 100  R3(config-router)#  redistribute igrp 200 metric 2000 200 255 1 1500  R3(config-router)# 

Next, look at R3's running configuration, the routing protocol portion of which is displayed in Example 11-14.

Example 11-14 R3's Running Configuration File
 R3#  show running-config  . . interface Serial1  description This interface connects to R5's S0 (DCE)  ip address 192.168.35.3 255.255.255.0 ! router eigrp 100  redistribute igrp 200 metric 2000 200 255 1 1500  network 192.168.100.0  network 192.168.3.0 ! router igrp 200  redistribute eigrp 100 metric 2000 200 255 1 1500  network 192.168.35.0  network 192.169.3.0 ! no ip classless ! banner motd ^CCC This is Router 3 ^C . . 

The highlighted portions illustrate where and how the commands appear in the configuration file. Next, go to R5 and take a look at the routing table to make sure that it is functioning correctly. Example 11-15 displays the IP routing table from R5.

Example 11-15 R5's IP Routing Table
 Termserver#  5  [Resuming connection 5 to r5 ... ] R5#  show ip route  Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2        E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR Gateway of last resort is not set  I    192.168.100.0/24 [100/10476] via 192.168.35.3, 00:00:51, Serial0  C    192.168.35.0/24 is directly connected, Serial0 C    192.168.50.0/24 is directly connected, TokenRing0  I    192.169.1.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0   I    192.168.1.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0   I    192.168.2.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0  I    192.169.3.0/24 [100/8976] via 192.168.35.3, 00:00:52, Serial0  I    192.168.3.0/24 [100/8576] via 192.168.35.3, 00:00:52, Serial0   I    192.169.2.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0   I    192.168.4.0/24 [100/10576] via 192.168.35.3, 00:00:52, Serial0  C    192.169.5.0/24 is directly connected, Loopback0  I    192.169.4.0/24 [100/10976] via 192.168.35.3, 00:00:52, Serial0  

IGRP makes it a little more difficult to determine which routes were introduced into IGRP through redistribution, but you know from the network diagram in Figure 11-1 that the highlighted routes were not originally in the IGRP domain. Another interesting note is that all of the RIP routes show up in the routing table as well. This is because you already redistributed between RIP and EIGRP, so when EIGRP was redistributed into IGRP, all of the RIP routes in addition to EIGRP routes were redistributed. Take a look at the highlighted individual routes:

 I    192.168.100.0/24 [100/10476] via 192.168.35.3, 00:00:51, Serial0 

This route is to the Frame Relay network. It was learned through EIGRP.

 I    192.169.1.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0 

This route is to R1's loopback 0 network. It was learned through EIGRP by RIP redistribution.

 I    192.168.1.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0 

This route is to R1 and R2's Ethernet 0 network. It was learned through EIGRP by RIP redistribution.

 I    192.168.2.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0 

This route is to R2's Ethernet 1 network. It was learned through EIGRP by RIP redistribution.

 I    192.168.3.0/24 [100/8576] via 192.168.35.3, 00:00:52, Serial0 

This route is to R3's Ethernet 0 network. It was learned through EIGRP redistribution.

 I    192.169.2.0/24 [100/10676] via 192.168.35.3, 00:00:52, Serial0 

This route is to R2's loopback 0 network. It was learned through EIGRP by RIP redistribution.

 I    192.168.4.0/24 [100/10576] via 192.168.35.3, 00:00:52, Serial0 

This route is to R4's Ethernet 0 network. Note that it was summarized to a /24 network. The actual subnet mask on R4's Ethernet 0 is /27. This is the same situation that was encountered on R2. EIGRP will autosummarize to the classful boundary before redistributing the route. IGRP is a classful routing protocol, so it does not understand any VLSMs.

 I    192.169.4.0/24 [100/10976] via 192.168.35.3, 00:00:52, Serial0 

This route is to R4's loopback 0 network. It was learned through EIGRP.

Notice that the 200.200.0.0/16 summary route is not present. This is the same situation as on R2. IGRP, being a classful routing protocol, does not understand CIDR. You can fix this problem using a default network. The key concept to remember when configuring a default network is that it does not have to be a directly connected network. This provides some flexibility in choosing how to route your network. The command to configure a default network is issued under the global configuration mode, and the syntax is as follows:

 Router(config)#  ip default-network   network-address  

The only thing to specify in this command is the network address. It is a good rule of thumb to choose a network that will nearly never go down. This is when a loopback interface is very useful. You could use R3's Ethernet 0 or Serial 0 interface, but once in a while the interface might go down. A loopback network will never go down unless the router goes down; then you might have more serious issues than a router that can't reach its default network! For purposes here, use R3's loopback 0 network (192.169.3.0) for the default network on R5. Example 11-16 displays the configuration command on R5.

Example 11-16 ip default-network Command on R5
 R5#  config t  Enter configuration commands, one per line.  End with CNTL/Z. R5(config)#  ip default-network 192.169.3.0  R5(config)# 

Next, take a look at the routing table on R5 in Example 11-17 to see how the default network appears in the routing table.

Example 11-17 R5's IP Routing Table
 R5(config)#  end  R5#  show ip route  %SYS-5-CONFIG_I: Configured from console by console R5#sho ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP        D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area        N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2        E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP        i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default        U - per-user static route, o - ODR  Gateway of last resort is 192.168.35.3 to network 192.169.3.0  I    192.168.100.0/24 [100/10476] via 192.168.35.3, 00:00:57, Serial0 C    192.168.35.0/24 is directly connected, Serial0 C    192.168.50.0/24 is directly connected, TokenRing0 I    192.169.1.0/24 [100/10676] via 192.168.35.3, 00:00:58, Serial0 I    192.168.1.0/24 [100/10676] via 192.168.35.3, 00:00:58, Serial0 I    192.168.2.0/24 [100/10676] via 192.168.35.3, 00:00:58, Serial0  I*   192.169.3.0/24 [100/8976] via 192.168.35.3, 00:00:58, Serial0  I    192.168.3.0/24 [100/8576] via 192.168.35.3, 00:00:58, Serial0 I    192.169.2.0/24 [100/10676] via 192.168.35.3, 00:00:58, Serial0 I    192.168.4.0/24 [100/10576] via 192.168.35.3, 00:00:58, Serial0 C    192.169.5.0/24 is directly connected, Loopback0 I    192.169.4.0/24 [100/10976] via 192.168.35.3, 00:00:58, Serial0 R5# 

From the highlighted portion in Example 11-17, the routing table shows two areas where the default network is identified. The first is the gateway of last resort statementR3's Serial 1 interface IP address at the top of the routing table. The second indicator of the location of the default network is where the router to R3's loopback 0 network has a * next to it. Even though the route was learned through IGRP (I), it can be a default network candidate. A default network is similar to the default route, but, as you remember, the default route was added to the routing table as a static route (S) with the * following it. A default network is not considered a static route or a default route, and it will not add an additional route entry in the routing table, as the default route statement will. It will designate an existing route in the routing table as a default path to reach only networks not present in the routing table. A default network statement can use any network in the routing table, not just a directly connected network. Example 11-18 displays the running configuration file of R5. Notice where the default network statement appears in the configuration file.

Example 11-18 R5's Running Configuration
 R5#  show running-config  Building configuration... Current configuration: ! . . router igrp 200  passive-interface Loopback0  network 192.168.35.0  network 192.168.50.0  network 192.169.5.0 ! no ip classless  ip default-network 192.169.3.0  ! banner motd ^CC This is Router 5 ^C . . . end R5# 

The ip default-network statement comes after the routing protocol configuration section.

Next, ping a few interfaces to verify connectivity into the EIGRP and RIP domains. For brevity in the lab we will not ping all of the interfaces, but in live environments you should ping all of the interfaces, just to verify for yourself. ping R1's Loopback 0 (192.169.1.1), R2's Ethernet 1 (192.168.2.2), R4's Loopback 1 (200.200.1.4), and R3's Serial 0 (192.168.100.3). Example 11-19 displays the results.

Example 11-19 R5 ping Results
 R5#  ping 192.169.1.1  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.169.1.1, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 32/35/44 ms R5#  ping 192.168.2.2  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.2.2, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 32/36/44 ms R5#  ping 200.200.1.4  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 200.200.1.4, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 60/62/64 ms R5#  ping 192.168.100.3  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.100.3, timeout is 2 seconds:  !!!!!   Success rate is 100 percent (5/5)  , round-trip min/avg/max = 4/5/8 ms R5# 

The 100-percent success rate confirms complete interrouting domain connectivity.

Lab Summary

To quickly review this chapter, you learned how to redistribute routes from one routing protocol to another. An issue that you need to remember when redistributing is that all metrics are lost and need to be manually set in the redistribute command. Redistributing routes between classful and classless routing protocols can cause some routes to be lost. Be aware of VLSM and CIDR routes when redistributing from a classless routing protocol (EIGRP) to a classful routing protocol (RIP or IGRP).

To compare the routing tables, Example 11-20 contains the routing tables for routers R1 through R5 after all of the route redistribution, default routes, and default networks have been configured.

Example 11-20 Routing Tables
 R1#  show ip route  Gateway of last resort is 192.168.1.2 to network 0.0.0.0 R    192.168.100.0/24 [120/1] via 192.168.1.2, 00:00:09, Ethernet0 R    192.168.35.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.168.50.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 C    192.169.1.0/24 is directly connected, Loopback0 C    192.168.1.0/24 is directly connected, Ethernet0 R    192.169.3.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.168.2.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.168.3.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.169.2.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.169.5.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.168.4.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 R    192.169.4.0/24 [120/1] via 192.168.1.2, 00:00:10, Ethernet0 S*   0.0.0.0/0 [1/0] via 192.168.1.2 _______________________________________________________________________ R2#  show ip route  Gateway of last resort is not set      192.168.4.0/27 is subnetted, 1 subnets D       192.168.4.0 [90/2707456] via 192.168.100.3, 1d01h, Serial0 D    192.169.4.0/24 [90/2809856] via 192.168.100.3, 1d01h, Serial0 D EX 192.169.5.0/24 [170/2809856] via 192.168.100.3, 23:49:13, Serial0 D EX 192.168.50.0/24 [170/2697984] via 192.168.100.3, 23:49:13, Serial0 D EX 192.168.35.0/24 [170/2169856] via 192.168.100.3, 23:49:13, Serial0 C    192.168.1.0/24 is directly connected, Ethernet0 R    192.169.1.0/24 [120/1] via 192.168.1.1, 00:00:25, Ethernet0 C    192.168.2.0/24 is directly connected, Ethernet1 C    192.169.2.0/24 is directly connected, Loopback0 C    192.168.100.0/24 is directly connected, Serial0 D    192.168.3.0/24 [90/2195456] via 192.168.100.3, 1d01h, Serial0 D EX 192.169.3.0/24 [170/2169856] via 192.168.100.3, 23:49:14, Serial0 D    200.200.0.0/16 [90/2809856] via 192.168.100.3, 1d01h, Serial0 _______________________________________________________________________ R3#  show ip route  Gateway of last resort is not set C    192.168.100.0/24 is directly connected, Serial0 C    192.168.35.0/24 is directly connected, Serial1 I    192.168.50.0/24 [100/8539] via 192.168.35.5, 00:00:25, Serial1 D EX 192.169.1.0/24 [170/2221056] via 192.168.100.2, 1d01h, Serial0 D EX 192.168.1.0/24 [170/2221056] via 192.168.100.2, 1d02h, Serial0 D EX 192.168.2.0/24 [170/2221056] via 192.168.100.2, 1d02h, Serial0 C    192.169.3.0/24 is directly connected, Loopback0 D EX 192.169.2.0/24 [170/2221056] via 192.168.100.2, 1d02h, Serial0 C    192.168.3.0/24 is directly connected, Ethernet0      192.168.4.0/27 is subnetted, 1 subnets D       192.168.4.0 [90/2195456] via 192.168.100.4, 2d06h, Serial0 I    192.169.5.0/24 [100/8976] via 192.168.35.5, 00:00:26, Serial1 D    192.169.4.0/24 [90/2297856] via 192.168.100.4, 1d01h, Serial0 D    200.200.0.0/16 [90/2297856] via 192.168.100.4, 2d06h, Serial0 _______________________________________________________________________ R4#  show ip route  Gateway of last resort is not set C    200.200.1.0/24 is directly connected, Loopback1 C    200.200.2.0/24 is directly connected, Loopback2 C    192.168.100.0/24 is directly connected, Serial0 D EX 192.168.35.0/24 [170/2169856] via 192.168.100.3, 23:38:54, Serial0 D EX 192.168.50.0/24 [170/2697984] via 192.168.100.3, 23:38:54, Serial0 D EX 192.169.1.0/24 [170/2733056] via 192.168.100.3, 1d01h, Serial0 D EX 192.168.1.0/24 [170/2733056] via 192.168.100.3, 1d02h, Serial0 D EX 192.169.3.0/24 [170/2169856] via 192.168.100.3, 23:38:54, Serial0 D EX 192.168.2.0/24 [170/2733056] via 192.168.100.3, 1d02h, Serial0 D EX 192.169.2.0/24 [170/2733056] via 192.168.100.3, 1d02h, Serial0 D    192.168.3.0/24 [90/2195456] via 192.168.100.3, 2d06h, Serial0 D EX 192.169.5.0/24 [170/2809856] via 192.168.100.3, 23:38:54, Serial0      192.168.4.0/27 is subnetted, 1 subnets C       192.168.4.0 is directly connected, Ethernet0 C    192.169.4.0/24 is directly connected, Loopback0 D    200.200.0.0/16 is a summary, 2d06h, Null0 _______________________________________________________________________ R5#  show ip route  Gateway of last resort is 192.168.35.3 to network 192.169.3.0 I    192.168.100.0/24 [100/10476] via 192.168.35.3, 00:01:14, Serial0 C    192.168.35.0/24 is directly connected, Serial0 C    192.168.50.0/24 is directly connected, TokenRing0 I    192.169.1.0/24 [100/10676] via 192.168.35.3, 00:01:14, Serial0 I    192.168.1.0/24 [100/10676] via 192.168.35.3, 00:01:14, Serial0 I    192.168.2.0/24 [100/10676] via 192.168.35.3, 00:01:14, Serial0 I*   192.169.3.0/24 [100/8976] via 192.168.35.3, 00:01:14, Serial0 I    192.168.3.0/24 [100/8576] via 192.168.35.3, 00:01:14, Serial0 I    192.169.2.0/24 [100/10676] via 192.168.35.3, 00:01:14, Serial0 I    192.168.4.0/24 [100/10576] via 192.168.35.3, 00:01:15, Serial0 C    192.169.5.0/24 is directly connected, Loopback0 I    192.169.4.0/24 [100/10976] via 192.168.35.3, 00:01:15, Serial0 _____________________________________________________________________ 

Compare this example to Example 11-1, introduced earlier in this chapter. You will see many changes and additions to the routing tables. The next chapter provides you with the opportunity to configure ISDN dial backup between routers R5 and R6.


   
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CCNA Practical Studies
CCNA Practical Studies (Cisco Certification & Training)
ISBN: 1587200465
EAN: 2147483647
Year: 2005
Pages: 127

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