OSPF Redistribution and Route Control

Lab 23: Default Routing, Route Manipulation, and Filtering in EIGRP Networks ”Part II

Lab Walkthrough

Configure the Frame Relay switch and attach the three routers in a back-to-back manner to the Frame switch. Use V.35 cables or CSU/DSUs with crossover cables to connect the routers. Create the four LANs by the use of switches or hubs/MAUs, as illustrated in Figure 11-14.

When the physical connections are complete, assign IP addresses to all LAN and WAN interfaces, as depicted in Figure 11-14. Be sure that you can ping each routers' local LAN and WAN interface before moving on. You will use frame-relay interface-dlci commands on the point-to-point interfaces among all the routers. Example 11-44 lists the Frame Relay configuration, to this point, on all routers involved.

Example 11-44 Frame Relay Configurations

  hostname solar_bucks   !  <<<text omitted>>>  !   interface Serial0   no ip address   no ip directed-broadcast   encapsulation frame-relay   no ip mroute-cache   frame-relay lmi-type cisco   !   interface Serial0.1 point-to-point   ip address 172.16.128.1 255.255.255.252   no ip directed-broadcast   frame-relay interface-dlci 121   !   interface Serial0.2 point-to-point   ip address 172.16.128.5 255.255.255.252   no ip directed-broadcast   frame-relay interface-dlci 111   !  _______________________________________________________________________  hostname g_and_s   !  <<<text omitted>>>  !   interface Serial0   no ip address   no ip directed-broadcast   encapsulation frame-relay   no ip mroute-cache   frame-relay lmi-type cisco   !   interface Serial0.1 point-to-point   ip address 172.16.128.2 255.255.255.252   no ip directed-broadcast   frame-relay interface-dlci 102   !   interface Serial0.2 point-to-point   ip address 172.16.128.9 255.255.255.252   no ip directed-broadcast   frame-relay interface-dlci 131   !  _______________________________________________________________________  hostname barneys   !  <<<text omitted>>>  !   interface Serial0   no ip address   encapsulation frame-relay   no ip mroute-cache   !   interface Serial0.1 point-to-point   ip address 172.16.128.6 255.255.255.252   frame-relay interface-dlci 110   !   interface Serial0.2 point-to-point   ip address 172.16.128.10 255.255.255.252   frame-relay interface-dlci 130   !  

The basic EIGRP configuration for this lab is far simpler than that of the previous lab. There are no discontinuous subnets; therefore, you do not have to disable EIGRP autosummarization. The Frame Relay network is a point-to-point network, thereby making split horizon a nonissue, as well. Following the three-step process for configuring EIGRP, you simply need to enable EIGRP routing and assign the AS number of 2001. You will use the network statement of 172.16.0.0 on each router. This is all that you need to configure for basic EIGRP routing. Because the PVCs to the g_and_s router are only 64 kbps, set the bandwidth to 64 on all the Frame Relay links to the g_and_s router. The EIGRP portion of the solar_bucks router, which resembles all the EIGRP configurations to this point, is presented in Example 11-45.

Example 11-45 EIGRP Configuration of All Routers to This Point

  !   router eigrp 2001   network 172.16.0.0   !  

At this time, you can verify routing by performing source ping s and examining the route table. When basic routing is working, you can proceed to the next portion of the lab, which requires that barneys not propagate the subnet 172.16.3.0 throughout the EIGRP domain. There are many ways to accomplish this, but for this lab, you will use a distribution list. The list will be applied to EIGRP updates leaving the s0.1 and s0.2 interfaces on the barneys router. Example 11-46 demonstrates the configuration of an access list denying the network 172.16.3.0/24 only. Access list 10 then is called by the distribution list in EIGRP. The distribution list must be applied to serial interfaces s0.1 and s0.2 to prevent the route from leaking back into the network.

Example 11-46 Configuration of a Distribution List

 barneys(config)#  access-list 10 deny 172.16.3.0 0.0.0.255  barneys(config)#  access-list 10 permit any  barneys(config)#  router eigrp 2001  barneys(config-router)#  distribute-list 10 out serial 0.1  barneys(config-router)#  distribute-list 10 out serial 0.2  barneys(config-router)#  ^z  

By observing the forwarding table on g_and_s in Example 11-47, you can see that the route 172.16.3.0/24 is now missing. You still can ping the 172.16.20.0/24 subnet, so you know that the filter was a success.

Example 11-47 Testing a Route Filter

 g_and_s#  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, ia - IS-IS inter area        * - candidate default, U - per-user static route, o - ODR        P - periodic downloaded static route Gateway of last resort is not set      172.16.0.0/16 is variably subnetted, 7 subnets, 3 masks C       172.16.128.8/30 is directly connected, Serial0.2 D       172.16.128.4/30 [90/41024000] via 172.16.128.1, 00:05:14, Serial0.1                         [90/41024000] via 172.16.128.10, 00:05:14, Serial0.2 C       172.16.128.0/30 is directly connected, Serial0.1 C       172.16.60.0/24 is directly connected, Ethernet0 D       172.16.50.0/24 [90/40537600] via 172.16.128.1, 00:05:14, Serial0.1 D       172.16.20.0/24 [90/40537600] via 172.16.128.10, 00:05:13, Serial0.2 D       172.16.0.0/16 is a summary, 01:10:38, Null0 g_and_s#  ping 172.16.20.1  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.20.1, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 40/41/44 ms g_and_s# 

The next portion of the lab requires solar_bucks to inject a default route into the EIGRP domain. To accomplish this task, configure a default static route pointing all traffic to the internet_routers Ethernet port, 172.16.50.1. For the routers to use the default network, ensure that IP classless is enabled. The static route is redistributed into EIGRP. Example 11-48 demonstrates the configuration of the default route on the solar_bucks router.

Example 11-48 Configuring a Default Route for EIGRP

 solar_bucks(config)#  ip route 0.0.0.0 0.0.0.0 172.16.50.1  solar_bucks(config)#  router eigrp 2001  solar_bucks(config-router)#  redistribute static  solar_bucks(config-router)#  default-metric 1544 100 254 1 1500  solar_bucks(config-router)#  ^Z  solar_bucks# 

By viewing the route or forwarding table on g_and_s or barneys, you can see that the default route is being propagated and is marked as an external, default candidate route, as shown in Example 11-49.

Example 11-49 Viewing the Default Route on Barneys

 g_and_s#  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 172.16.128.1 to network 0.0.0.0  172.16.0.0/16 is variably subnetted, 7 subnets, 3 masks C       172.16.128.8/30 is directly connected, Serial0.2 D       172.16.128.4/30 [90/41024000] via 172.16.128.1, 00:20:43, Serial0.1                         [90/41024000] via 172.16.128.10, 00:20:43, Serial0.2 C       172.16.128.0/30 is directly connected, Serial0.1 C       172.16.60.0/24 is directly connected, Ethernet0 D       172.16.50.0/24 [90/40537600] via 172.16.128.1, 00:20:43, Serial0.1 D       172.16.20.0/24 [90/40537600] via 172.16.128.10, 00:20:42, Serial0.2 D       172.16.0.0/16 is a summary, 01:26:07, Null0  D*EX 0.0.0.0/0 [170/40537600] via 172.16.128.1, 00:09:12, Serial0.1  g_and_s# 

The final phase of the lab involves influencing EIGRP routing decisions. In the previous example, g_and_s is using solar_bucks as the preferred route to the Internet. By changing the delay on this link, you can affect the route table so that the barneys router is the preferred path to the Internet. To accomplish this, use the delay 1000 command on each side of the PVC going between the g_and_s router and solar_bucks. Example 11-50 lists the route table of g_and_s, showing all routes now going through barneys first. A source trace can be performed to further test the configuration.

Example 11-50 Route Table of g_and_s After the Delay Was Implemented

 g_and_s#  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, ia - IS-IS inter area        * - candidate default, U - per-user static route, o - ODR        P - periodic downloaded static route Gateway of last resort is 172.16.128.10 to network 0.0.0.0      172.16.0.0/16 is variably subnetted, 7 subnets, 3 masks C       172.16.128.8/30 is directly connected, Serial0.2  D       172.16.128.4/30 [90/41024000] via 172.16.128.10, 00:00:01, Serial0.2  C       172.16.128.0/30 is directly connected, Serial0.1 C       172.16.60.0/24 is directly connected, Ethernet0  D       172.16.50.0/24 [90/41049600] via 172.16.128.10, 00:00:01, Serial0.2   D       172.16.20.0/24 [90/40537600] via 172.16.128.10, 00:00:11, Serial0.2  D       172.16.0.0/16 is a summary, 01:28:54, Null0  D*EX 0.0.0.0/0 [170/41049600] via 172.16.128.10, 00:00:02, Serial0.2  g_and_s# 

Example 11-51 lists the final configurations.

Example 11-51 Final Router Configurations for the Internet Coffee Shop Network

  hostname solar_bucks   !  <<<text omitted>>>  !   interface Ethernet0   ip address 172.16.50.5 255.255.255.0   no ip directed-broadcast   !   interface Serial0   no ip address   no ip directed-broadcast   encapsulation frame-relay   no ip mroute-cache   frame-relay lmi-type cisco   !   interface Serial0.1 point-to-point   bandwidth 64   ip address 172.16.128.1 255.255.255.252   no ip directed-broadcast   delay 1000   frame-relay interface-dlci 121   !   interface Serial0.2 point-to-point   ip address 172.16.128.5 255.255.255.252   no ip directed-broadcast   frame-relay interface-dlci 111   !  <<<text omitted>>>  !   router eigrp 2001   redistribute static    network 172.16.50.0 0.0.0.255        Optional 12.0 way, listed for example only    network 172.16.0.0   default-metric 1544 100 254 1 1500   !   ip classless   ip route 0.0.0.0 0.0.0.0 172.16.50.1  _______________________________________________________________________  hostname g_and_s   !  <<<text omitted>>>  !   interface Ethernet0   ip address 172.16.60.1 255.255.255.0   no ip directed-broadcast   !   interface Serial0   no ip address   no ip directed-broadcast   encapsulation frame-relay   no ip mroute-cache   frame-relay lmi-type cisco   !   interface Serial0.1 point-to-point   bandwidth 64   ip address 172.16.128.2 255.255.255.252   no ip directed-broadcast   delay 1000   frame-relay interface-dlci 102   !   interface Serial0.2 point-to-point   bandwidth 64   ip address 172.16.128.9 255.255.255.252   no ip directed-broadcast   frame-relay interface-dlci 131   !   router eigrp 2001   network 172.16.0.0   !   ip classless  _______________________________________________________________________  hostname barneys   !  <<<text omitted>>>  !   interface Ethernet2   ip address 172.16.20.1 255.255.255.0   media-type 10BaseT   !   <<<text omitted>>>   !   interface Serial0   no ip address   encapsulation frame-relay   no ip mroute-cache   !   interface Serial0.1 point-to-point   ip address 172.16.128.6 255.255.255.252   frame-relay interface-dlci 110   !   interface Serial0.2 point-to-point   ip address 172.16.128.10 255.255.255.252   bandwidth 64   frame-relay interface-dlci 130   !  <<<text omitted>>>  !   router eigrp 2001   network 172.16.0.0   distribute-list 10 out Serial0.1   distribute-list 10 out Serial0.2   !   ip classless   !   access-list 10 deny   172.16.3.0 0.0.0.255   access-list 10 permit any