Answers to Chapter 1 Configuration Exercises

1:	Autonomous System 65531 in Figure 1-14 is a core AS. Figure 1-14. The Internetwork for Configuration Exercise 1 Configure EGP on RTA and RTB, with the following constraints: - The data link interior to the AS is not advertised to any exterior neighbor. - RTA advertises the network attached to its S1 interface to RTB; with this exception, no other inter-AS link is advertised between RTA and RTB. - RTA and RTB advertise a default route to their exterior neighbors in addition to networks learned from other autonomous systems. Neither gateway advertises a default route to its internal neighbor.
A:	The configurations of RTA and RTB are as follows : hostname RTA ! interface Ethernet0 ip address 192.168.1.1 255.255.255.0 ! interface Serial0 ip address 192.168.2.1 255.255.255.0 ! interface Serial1 ip address 192.168.3.1 255.255.255.0 ! interface Serial2 ip address 192.168.4.1 255.255.255.0 ! autonomous-system 65531 ! router egp 0 network 192.168.3.0 neighbor 192.168.1.2 neighbor any default-information originate distribute-list 1 out Ethernet0 ! access-list 1 deny 0.0.0.0 access-list 1 permit any __________________________________________________________________ hostname RTB ! interface Ethernet0 ip address 192.168.1.2 255.255.255.0 ! interface Serial0 ip address 192.168.5.1 255.255.255.0 ! autonomous-system 65531 ! router egp 0 neighbor any default-information originate distribute-list 1 out Ethernet0 ! access-list 1 deny 0.0.0.0 access-list 1 permit any
2:	Example 1-26 shows the route table of RTC in Figure 1-15. Example 2-26 The Route Table of RTC in Figure 1-15 RTC# 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 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 Gateway of last resort is not set I 192.168.105.0 [100/8976] via 192.168.6.2, 00:01:00, Serial1 I 192.168.110.0 [100/8976] via 192.168.6.2, 00:01:00, Serial1 I 192.168.100.0 [100/8976] via 192.168.10.2, 00:01:00, Serial2 I 192.168.120.0 [100/8976] via 192.168.10.2, 00:01:01, Serial2 C 192.168.2.0 is directly connected, Serial0 C 192.168.6.0 is directly connected, Serial1 C 192.168.10.0 is directly connected, Serial2 RTC# Figure 1-15. The Internetwork for Configuration Exercise 2 Using redistribution, configure RTC to advertise all EGP-learned networks into AS 65510, and all internal networks except 192.168.105.0 to the core AS. Protect against route feedback by ensuring that none of the networks internal to AS 65510 are advertised back via EGP. The process ID in this configuration is the same as the local AS number.
A:	The relevant configuration of RTC is as follows: autonomous-system 65510 ! router igrp 65510 redistribute egp 65531 metric 1544 100 255 1 1500 network 192.168.6.0 ! router egp 65531 redistribute igrp 65510 neighbor 192.168.2.1 distribute-list 10 out Serial0 distribute-list 20 in Serial0 ! access-list 10 deny 192.168.105.0 access-list 10 permit any access-list 20 deny 192.168.105.0 access-list 20 deny 192.168.110.0 access-list 20 deny 192.168.100.0 access-list 20 deny 192.168.120.0 access-list 20 deny 192.168.10.0 access-list 20 deny 192.168.6.0 access-list 20 permit any Notice that no metric is specified for the redistribution into EGP; EGP adds a default metric of 3. In this example, the distribute-list command is used to filter routes, although a route map could also be used for the same purpose. Of particular interest is the filter that blocks internal network addresses if they are included in incoming EGP updates. Even though 192.168.105.0 is not being advertised out of the AS, the address is included in access list 20. This guards against the possibility of the network's finding its way into the EGP domain by some other means and then being routed back into AS 65510. It also guards against the possibility of a duplicate network address entering the AS.
3:	Example 1-27 shows the route table of RTD in Figure 1-15. Example 1-27 The Route Table of RTD in Figure 1-15 RTD# 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 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 Gateway of last resort is not set C 192.168.3.0 is directly connected, Serial0 C 192.168.7.0 is directly connected, Serial1 R 192.168.230.0 [120/1] via 192.168.7.2, 00:00:14, Serial1 R 192.168.200.0 [120/2] via 192.168.7.2, 00:00:15, Serial1 R 192.168.220.0 [120/1] via 192.168.7.2, 00:00:15, Serial1 R 192.168.210.0 [120/2] via 192.168.7.2, 00:00:15, Serial1 RTD# Configure RTD with the following parameters: - Only 192.168.220.0 and 192.168.230.0 are to be advertised to AS 65531. - No routing protocol is redistributed into EGP. - EGP is redistributed into the IGP of AS 65515. - 192.168.3.0 is advertised into AS 65515 with a metric of 1. - 192.168.100.0, from RTC, is advertised into AS 65515 with a metric of 1. - 192.168.120.0, from RTC, is advertised into AS 65515 with a metric of 3. - All other routes are advertised into AS 65515 with a metric of 5.
A:	The relevant configuration of RTD is as follows: autonomous-system 65515 ! router rip redistribute egp 65531 route-map EXTERNAL network 192.168.7.0 network 192.168.3.0 default-metric 5 ! router egp 65531 network 192.168.220.0 network 192.168.230.0 neighbor 192.168.3.1 ! access-list 10 permit 192.168.100.0 access-list 20 permit 192.168.120.0 access-list 30 permit any ! route-map EXTERNAL permit 10 match ip address 10 set metric 1 ! route-map EXTERNAL permit 20 match ip address 20 set metric 3 ! route-map EXTERNAL permit 30 match ip address 30
4:	Example 1-28 shows the route table of RTE in Figure 1-15. Example 1-28 The Route Table of RTE in Figure 1-15 RTE# 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 O 192.168.125.0/28 [110/74] via 192.168.130.6, 00:01:03, Serial1 C 192.168.4.0/24 is directly connected, Serial0 192.168.225.0/28 is subnetted, 1 subnets O E2 192.168.225.160 [110/50] via 192.168.130.18, 00:01:04, Ethernet0 192.168.215.0/24 is variably subnetted, 3 subnets, 3 masks O 192.168.215.161/32 [110/65] via 192.168.130.6, 00:01:04, Serial1 O E2 192.168.215.192/26 [110/50] via 192.168.130.18, 00:01:04, Ethernet0 O E1 192.168.215.96/28 [110/164] via 192.168.130.6, 00:01:04, Serial1 192.168.130.0/24 is variably subnetted, 7 subnets, 4 masks D 192.168.131.192/27 [90/2195456] via 192.168.130.6, 00:16:49, Serial1 D 192.168.131.96/27 [90/409600] via 192.168.130.18, 00:16:49, Ethernet0 O 192.168.131.97/32 [110/11] via 192.168.130.18, 00:01:05, Ethernet0 D 192.168.131.64/27 [90/409600] via 192.168.130.18, 00:15:01, Ethernet0 D 192.168.131.8/30 [90/2195456] via 192.168.130.6, 00:16:49, Serial1 C 192.168.131.4/30 is directly connected, Serial1 C 192.168.131.16/28 is directly connected, Ethernet0 RTE# Configure RTE with the following parameters: - No IGP is redistributed into EGP. - EGP is not redistributed into any IGP. - All the internal networks of AS 65520 are advertised to AS 65531. - The internal routers of AS 65520 can forward packets to any network advertised by RTA. - All process IDs are the same as the AS number. - All OSPF interfaces are in area 0.
A:	The relevant configuration of RTE is as follows: autonomous-system 65520 ! router eigrp 65520 redistribute static network 192.168.130.0 default-metric 1000 100 255 1 1500 no auto-summary ! router ospf 65520 redistribute static metric 10 subnets network 192.168.130.4 0.0.0.3 area 0 network 192.168.130.16 0.0.0.15 area 0 ! router egp 65531 network 192.168.125.0 network 192.168.131.0 network 192.168.215.0 network 192.168.225.0 neighbor 192.168.4.1 ! ip route 0.0.0.0 0.0.0.0 192.168.4.1
5:	In Figure 1-16, AS 65525 has been added to the internetwork of the previous exercises. RTF's Ethernet interface has an IP address of 192.168.1.3/24. Figure 1-16. The Internetwork for Configuration Exercise 5 Configure this router to peer only with RTB and make any necessary configuration changes to support third-party neighbors.
A:	The configurations of RTF and RTB are as follows: RTF autonomous-system 65525 ! router egp 65531 network 192.168.50.0 neighbor 192.168.1.2 ________________________________________________________________ RTB autonomous-system 65531 ! router egp 0 neighbor 192.168.1.1 neighbor 192.168.1.1 third-party 192.168.1.3 external neighbor 192.168.1.3 neighbor 192.168.1.3 third-party 192.168.1.1 neighbor any default-information originate distribute-list 1 out Ethernet0 ! access-list 1 deny 0.0.0.0 access-list 1 permit any