| 1: | AS 1 in Table 3-4 is a transit AS, and the IGP is OSPF. Area 0 spans the entire AS. No networks internal to the AS are advertised outside of the AS. None of the subnets over which EBGP is run should be advertised into AS 1. Write BGP configurations for the routers in AS 1, putting all internal neighbors in a peer group called LOCAL. For R3 only, EBGP peering should be performed between loopback interfaces. Authenticate all IBGP connections with the password ExeRCise1. |
| A: | [click here] R1 router ospf 1 network 10.255.255.1 0.0.0.0 area 0 network 192.168.100.5 0.0.0.0 area 0 network 192.168.100.13 0.0.0.0 area 0 ! router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.2 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.2 remote-as 2 __________________________________________________________________ R2 router ospf 1 network 10.255.255.2 0.0.0.0 area 0 network 192.168.100.6 0.0.0.0 area 0 network 192.168.100.17 0.0.0.0 area 0 ! router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.1 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.10 remote-as 2 neighbor 192.168.100.58 remote-as 6 __________________________________________________________________ R3 router ospf 1 network 10.255.255.3 0.0.0.0 area 0 network 192.168.100.18 0.0.0.0 area 0 network 192.168.100.21 0.0.0.0 area 0 ! router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor REMOTE peer-group neighbor REMOTE ebgp-multihop 2 neighbor REMOTE update-source Loopback0 neighbor 10.255.255.1 peer-group LOCAL neighbor 10.255.255.2 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.26 peer-group REMOTE neighbor 192.168.100.26 remote-as 3 _________________________________________________________________ R4 router ospf 1 network 10.255.255.4 0.0.0.0 area 0 network 192.168.100.14 0.0.0.0 area 0 network 192.168.100.22 0.0.0.0 area 0 ! router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.1 peer-group LOCAL neighbor 10.255.255.2 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.30 remote-as 4 neighbor 192.168.100.34 remote-as 5 |
| 2: | AS 2 in Table 3-4 is a stub (nontransit) AS, and its IGP is EIGRP. Configure the routers in AS 2 to speak EBGP to any external peers and to redistribute any EIGRP routes into BGP. Redistribute BGP-learned routes into EIGRP. Implement any necessary filters to prevent incorrect routes from being redistributed. |
| A: | [click here] R5 router eigrp 2 redistribute bgp 2 route-map External_Routes metric 10000 100 255 1 1500 passive-interface Serial0 network 192.168.1.0 network 192.168.100.0 no auto-summary ! router bgp 2 redistribute eigrp 2 route-map Internal_Routes neighbor 192.168.100.1 remote-as 1 ! ip as-path access-list 1 deny _2_ ip as-path access-list 1 permit .* ip as-path access-list 2 permit ^$ ! route-map External_Routes permit 10 match as-path 1 ! route-map Internal_Routes permit 10 match as-path 2 __________________________________________________________________ R6 router eigrp 2 redistribute bgp 2 route-map External_Routes metric 10000 100 255 1 1500 passive-interface Serial0 network 192.168.1.0 network 192.168.100.0 no auto-summary ! router bgp 2 redistribute eigrp 2 route-map Internal_Routes neighbor 192.168.100.9 remote-as 1 ! ip as-path access-list 1 deny _2_ ip as-path access-list 1 permit .* ip as-path access-list 2 permit ^$ ! route-map External_Routes permit 10 match as-path 1 ! route-map Internal_Routes permit 10 match as-path 2 |
| 3: | Networks 192.168.1.0, 192.168.2.0, 192.168.3.0, 192.168.4.0, and 192.168.5.0 exist within AS 2. The administrator of this AS wants the neighboring AS to prefer R5 when sending traffic to 192.168.1.0 and 192.168.3.0. The neighboring AS should prefer R6 when sending traffic to 192.168.2.0 and 192.168.4.0. In each case, the less-preferred link serves as a backup to the more-preferred link. 192.168.5.0 is a private network and must not be advertised to any EBGP peer. Modify the configurations written in Exercise 2 to implement this policy. |
| A: | Note that in these configurations, the AS_PATH filters from Exercise 2 remain . Although not entirely necessary due to the access lists filtering specific prefixes, in a real network they can act as an extra bit of insurance against the wrong routes being advertised. R5 router eigrp 2 redistribute bgp 2 route-map External_Routes metric 10000 100 255 1 1500 passive-interface Serial0 network 192.168.1.0 network 192.168.100.0 no auto-summary ! router bgp 2 redistribute eigrp 2 route-map Internal_Routes neighbor 192.168.100.1 remote-as 1 ! ip as-path access-list 1 deny _2_ ip as-path access-list 1 permit .* ip as-path access-list 2 permit ^$ ! access-list 1 permit 192.168.1.0 access-list 1 permit 192.168.3.0 access-list 2 permit 192.168.2.0 access-list 2 permit 192.168.4.0 ! route-map External_Routes permit 10 match as-path 1 ! route-map Internal_Routes permit 10 match ip address 1 match as-path 2 set metric 50 ! route-map Internal_Routes permit 20 match ip address 2 match as-path 2 set metric 150 __________________________________________________________________ R6 router eigrp 2 redistribute bgp 2 route-map External_Routes metric 10000 100 255 1 1500 passive-interface Serial0 network 192.168.1.0 network 192.168.100.0 no auto-summary ! router bgp 2 redistribute eigrp 2 route-map Internal_Routes neighbor 192.168.100.9 remote-as 1 ! ip as-path access-list 1 deny _2_ ip as-path access-list 1 permit .* ip as-path access-list 2 permit ^$ ! access-list 1 permit 192.168.2.0 access-list 1 permit 192.168.4.0 access-list 2 permit 192.168.1.0 access-list 2 permit 192.168.3.0 ! route-map External_Routes permit 10 match as-path 1 ! route-map Internal_Routes permit 10 match ip address 1 match as-path 2 set metric 50 ! route-map Internal_Routes permit 20 match ip address 2 match as-path 2 set metric 150 |
| 4: | Configure the EBGP neighbors of R5 and R6 to advertise a default route to AS 2. No other routes are to be advertised. |
| A: | [click here] R1 router ospf 1 network 10.255.255.1 0.0.0.0 area 0 network 192.168.100.5 0.0.0.0 area 0 network 192.168.100.13 0.0.0.0 area 0 ! router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.2 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.2 remote-as 2 neighbor 192.168.100.2 default-originate neighbor 192.168.100.2 distribute-list 1 out ! access-list 1 permit 0.0.0.0 access-list 1 deny any __________________________________________________________________ R2 router ospf 1 network 10.255.255.2 0.0.0.0 area 0 network 192.168.100.6 0.0.0.0 area 0 network 192.168.100.17 0.0.0.0 area 0 ! router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.1 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.10 remote-as 2 neighbor 192.168.100.10 default-originate neighbor 192.168.100.10 distribute-list 1 out neighbor 192.168.100.58 remote-as 6 ! access-list 1 permit 0.0.0.0 access-list 1 deny any |
| 5: | The administrator of AS 2's neighboring AS disagrees with part of the policy set in Exercise 2. He wants all routers in his AS to send traffic destined for 192.168.3.0 to R6, with R5 as a backup. All traffic destined for 192.168.4.0 should be sent to R5, with R6 as a backup. The rest of the policy set in Exercise 2 is acceptable. Write configurations to implement this policy. |
| A: | Remember that LOCAL_PREF is considered ahead of MED in the BGP decision process. Therefore, changing the default LOCAL_PREF attributes of the appropriate routes on the appropriate routers in AS 2 overrides the routes' MEDs. R1 router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.2 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.2 remote-as 2 neighbor 192.168.100.2 route-map SET_PREF in neighbor 192.168.100.2 default-originate neighbor 192.168.100.2 distribute-list 1 out ! access-list 1 permit 0.0.0.0 access-list 1 deny any access-list 2 permit 192.168.4.0 access-list 2 deny any ! route-map SET_PREF permit 10 match ip address 2 set local-preference 200 ! route-map SET_PREF permit 20 __________________________________________________________________ R2 router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.1 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.10 remote-as 2 neighbor 192.168.100.10 route-map SET_PREF in neighbor 192.168.100.10 default-originate neighbor 192.168.100.10 distribute-list 1 out neighbor 192.168.100.58 remote-as 6 ! access-list 1 permit 0.0.0.0 access-list 1 deny any access-list 2 permit 192.168.3.0 access-list 2 deny any ! route-map SET_PREF permit 10 match ip address 2 set local-preference 200 ! route-map SET_PREF permit 20 |
| 6: | AS 3 in Table 3-4 is a stub AS, and AS 4 is a transit AS. The IGP of both autonomous systems is OSPF, and the internal interfaces of R7 and R8 are both in area 0. Write BGP and OSPF configurations for R7 and R8, advertise the internal addresses shown in Table 3-5 to all EBGP peers, and ensure that routers in the OSPF domains can reach any external destination. Do not redistribute routes in either direction. Also, ensure that the BGP router ID of R7 is 192.168.3.254. |
| A: | The route-map STUB at R7 prevents routes received from an EBGP peer from being advertised to other EBGP peers, thus making the AS nontransit. R8 has no such route filter, so AS 4 is a transit AS. R7 router ospf 3 network 10.255.255.7 0.0.0.0 area 0 network 172.16.1.1 0.0.0.0 area 0 default-information originate ! router bgp 3 bgp router-id 192.168.3.254 network 172.16.1.0 mask 255.255.255.0 network 172.16.3.0 mask 255.255.255.0 network 172.17.0.0 network 192.168.6.128 mask 255.255.255.128 neighbor 192.168.100.25 remote-as 1 neighbor 192.168.100.25 ebgp-multihop 2 neighbor 192.168.100.25 update-source Loopback0 neighbor 192.168.100.25 route-map STUB out neighbor 192.168.100.38 remote-as 4 neighbor 192.168.100.38 route-map STUB out neighbor 192.168.100.42 remote-as 5 neighbor 192.168.100.42 route-map STUB out no auto-summary ! ip route 0.0.0.0 0.0.0.0 Null0 ! ip as-path access-list 1 permit ^$ ! route-map STUB permit 10 match as-path 1 __________________________________________________________________ R8 router ospf 4 network 10.255.255.8 0.0.0.0 area 0 network 172.16.2.1 0.0.0.0 area 0 default-information originate ! router bgp 4 network 172.16.2.0 mask 255.255.255.0 network 172.16.4.0 mask 255.255.255.0 network 172.18.0.0 network 192.168.6.0 mask 255.255.255.128 neighbor 192.168.100.29 remote-as 1 neighbor 192.168.100.37 remote-as 3 neighbor 192.168.100.46 remote-as 5 no auto-summary ! ip route 0.0.0.0 0.0.0.0 Null0 Table 3-5. Destinations Internal to AS 3 and AS 4 | AS 3 | AS 4 | | 172.16.1.0/24 | 172.16.2.0/24 | | 172.16.3.0/24 | 172.16.4.0/24 | | 172.17.0.0/16 | 172.18.0.0/16 | | 192.168.6.128/25 | 192.168.6.0/25 | |
| 7: | Modify the configurations of Exercise 6 so that R7 and R8 speak OSPF across the link directly connecting them; remove BGP from the link. Traffic between subnets 172.16.3.0/24 and 172.16.4.0/24 should prefer this direct link and should use any EBGP links only as backup. Traffic between the other addresses internal to AS 3 and AS 4 should use the EBGP links and should use the direct link only as a backup. Additionally, traffic from other autonomous systems can use the direct link as a backup route. If an EBGP link to AS 4 fails, for example, the neighboring AS can send traffic destined for AS 4 to AS 3, to be forwarded to AS 4 across the direct link. |
| A: | [click here] R7 router ospf 3 network 10.255.255.7 0.0.0.0 area 0 network 172.16.1.1 0.0.0.0 area 0 network 192.168.100.37 0.0.0.0 area 0 default-information originate ! router bgp 3 bgp router-id 192.168.3.254 network 172.16.1.0 mask 255.255.255.0 network 172.16.3.0 mask 255.255.255.0 backdoor network 172.17.0.0 network 192.168.6.128 mask 255.255.255.128 neighbor 192.168.100.25 remote-as 1 neighbor 192.168.100.25 ebgp-multihop 2 neighbor 192.168.100.25 update-source Loopback0 neighbor 192.168.100.25 route-map STUB out neighbor 192.168.100.42 remote-as 5 neighbor 192.168.100.42 route-map STUB out no auto-summary ! ip route 0.0.0.0 0.0.0.0 Null0 ! ip as-path access-list 1 permit ^$ ! route-map STUB permit 10 match as-path 1 __________________________________________________________________ R8 router ospf 4 network 10.255.255.8 0.0.0.0 area 0 network 172.16.2.1 0.0.0.0 area 0 network 192.168.100.38 0.0.0.0 area 0 default-information originate ! router bgp 4 network 172.16.2.0 mask 255.255.255.0 network 172.16.4.0 mask 255.255.255.0 backdoor network 172.18.0.0 network 192.168.6.0 mask 255.255.255.128 neighbor 192.168.100.29 remote-as 1 neighbor 192.168.100.46 remote-as 5 no auto-summary ! ip route 0.0.0.0 0.0.0.0 Null0 |
| 8: | AS 5 in Table 3-4 is a transit AS, and its IGP is IS-IS. The Level 2 area 47.0001 spans the entire AS. The internal networks are 192.168.9.0, 192.168.10.0, 192.168.11.0, and 192.168.12.0. Write IS-IS and BGP configurations for R9, R10, and R11. Ensure that all external routes are known by the routers in the IS-IS domain and that all internal networks are advertised to all EBGP peers. Do not redistribute IS-IS routes into BGP. |
| A: | These configurations use next-hop-self, although alternatively you could run IS-IS in passive mode on the external interfaces. R9 router isis net 47.0001.0000.1234.abcd.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 network 192.168.12.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.10 peer-group LOCAL neighbor 10.255.255.11 peer-group LOCAL neighbor 192.168.100.41 remote-as 3 __________________________________________________________________ R10 router isis net 47.0001.0000.5678.ef01.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 network 192.168.12.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.9 peer-group LOCAL neighbor 10.255.255.11 peer-group LOCAL neighbor 192.168.100.45 remote-as 4 __________________________________________________________________ R11 router isis net 47.0001.0000.4321.dcba.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 network 192.168.12.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.9 peer-group LOCAL neighbor 10.255.255.10 peer-group LOCAL neighbor 192.168.100.33 remote-as 1 |
| 9: | Modify the configurations written in Exercise 8 so that network 192.168.12.0 is known only by AS 4, and no other autonomous system. |
| A: | The network statement for 192.168.12.0 is removed from the configurations of R9 and R11 so that they do not advertise that network. At R10, the NO_EXPORT community is added to the route to 192.168.12.0 so that it is not advertised beyond AS 4. R9 router isis net 47.0001.0000.1234.abcd.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.10 peer-group LOCAL neighbor 10.255.255.11 peer-group LOCAL neighbor 192.168.100.41 remote-as 3 __________________________________________________________________ R10 router isis net 47.0001.0000.5678.ef01.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 network 192.168.12.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.9 peer-group LOCAL neighbor 10.255.255.11 peer-group LOCAL neighbor 192.168.100.45 remote-as 4 neighbor 192.168.100.45 send-community neighbor 192.168.100.45 route-map EXPORT_COMMUNITY out ! access-list 1 permit 192.168.12.0 ! route-map EXPORT_COMMUNITY permit 10 match ip address 1 set community no-export ! route-map EXPORT_COMMUNITY permit 20 __________________________________________________________________ R11 router isis net 47.0001.0000.4321.dcba.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.9 peer-group LOCAL neighbor 10.255.255.10 peer-group LOCAL neighbor 192.168.100.33 remote-as 1 |
| 10: | Modify the configurations written in Exercise 9 so that AS 3 and AS 4 prefer the path through AS 1 to reach network 192.168.11.0. |
| A: | Network 192.168.11.0 is advertised normally by R11 but is prepended by R9 and R10. R9 router isis net 47.0001.0000.1234.abcd.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.10 peer-group LOCAL neighbor 10.255.255.11 peer-group LOCAL neighbor 192.168.100.41 remote-as 3 neighbor 192.168.100.41 route-map PREPEND out ! access-list 1 permit 192.168.11.0 ! route-map PREPEND permit 10 match ip address 1 set as-path prepend 5 5 ! route-map PATH permit 20 __________________________________________________________________ R10 router isis net 47.0001.0000.5678.ef01.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 network 192.168.12.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.9 peer-group LOCAL neighbor 10.255.255.11 peer-group LOCAL neighbor 192.168.100.45 remote-as 4 neighbor 192.168.100.45 send-community neighbor 192.168.100.45 route-map EXPORT_COMMUNITY out ! access-list 1 permit 192.168.12.0 access-list 2 permit 192.168.11.0 ! route-map EXPORT_COMMUNITY permit 10 match ip address 1 set community no-export ! route-map EXPORT_COMMUNITY permit 20 match ip address 1 set as-path prepend 5 5 ! route-map EXPORT_COMMUNITY permit 30 __________________________________________________________________ R11 router isis net 47.0001.0000.4321.dcba.00 is-type level-2-only redistribute bgp 5 metric 0 metric-type external level-2 ! router bgp 5 network 192.168.9.0 network 192.168.10.0 network 192.168.11.0 neighbor LOCAL peer-group neighbor LOCAL remote-as 5 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.9 peer-group LOCAL neighbor 10.255.255.10 peer-group LOCAL neighbor 192.168.100.33 remote-as 1 |
| 11: | The networks internal to AS 6 in Table 3-4 are 192.168.16.0, 192.168.17.0, 192.168.18.0, and 192.168.19.0. Write a BGP configuration for R12 that advertises these networks to the neighboring AS and that also advertises a summary route for the networks. The neighboring AS should advertise only the summary to other autonomous systems. |
| A: | [click here] router bgp 6 network 192.168.16.0 network 192.168.17.0 network 192.168.18.0 network 192.168.19.0 aggregate-address 192.168.16.0 255.255.252.0 neighbor 192.168.100.57 remote-as 1 neighbor 192.168.100.57 send-community neighbor 192.168.100.57 route-map AGGREGATE out ! access-list 101 permit ip host 192.168.16.0 host 255.255.252.0 ! route-map AGGREGATE permit 10 match ip address 101 set community none ! route-map AGGREGATE permit 20 set community no-export |
| 12: | Modify the most recent configuration you wrote for R12's EBGP neighbor so that the neighbor does not accept prefixes that do not belong to the aggregate being advertised by R12, does not accept prefixes longer than 24 bits, and does not accept more than five prefixes. |
| A: | [click here] R2 router bgp 1 neighbor LOCAL peer-group neighbor LOCAL remote-as 1 neighbor LOCAL password 7 15371309360922372D62 neighbor LOCAL update-source Loopback0 neighbor LOCAL next-hop-self neighbor 10.255.255.1 peer-group LOCAL neighbor 10.255.255.3 peer-group LOCAL neighbor 10.255.255.4 peer-group LOCAL neighbor 192.168.100.10 remote-as 2 neighbor 192.168.100.10 route-map SET_PREF in neighbor 192.168.100.10 default-originate neighbor 192.168.100.10 distribute-list 1 out neighbor 192.168.100.58 remote-as 6 neighbor 192.168.100.58 maximum-prefix 5 neighbor 192.168.100.58 route-map PREFIX_LIMIT in ! access-list 1 permit 0.0.0.0 access-list 1 deny any access-list 2 permit 192.168.3.0 access-list 2 deny any ! ip prefix-list AS6 seq 5 permit 192.168.16.0/22 le 24 ! route-map SET_PREF permit 10 match ip address 2 set local-preference 200 ! route-map SET_PREF permit 20 ! route-map PREFIX_LIMIT permit 10 match ip address prefix-list AS6 |
| 13: | Example 3-164 shows a BGP configuration for R7 in Table 3-4. The internal prefixes shown in Table 3-5 are advertised by OSPF. Example 3-164 BGP Configuration of Router R7 router bgp 3 redistribute ospf 1 neighbor NEIGHBORS peer-group neighbor NEIGHBORS ebgp-multihop 2 neighbor NEIGHBORS update-source Loopback0 neighbor NEIGHBORS route-map EX13 out neighbor 10.255.255.8 remote-as 4 neighbor 10.255.255.8 peer-group NEIGHBORS neighbor 10.255.255.9 remote-as 5 neighbor 10.255.255.9 peer-group NEIGHBORS neighbor 10.255.255.3 remote-as 1 neighbor 10.255.255.3 peer-group NEIGHBORS no auto-summary ! ip classless ip as-path access-list 1 permit ^1 2$ ! access-list 1 permit 172.16.1.0 access-list 2 permit 172.16.3.0 ! route-map EX13 permit 10 match ip address 1 set as-path prepend 2 ! route-map EX13 permit 20 match ip address 2 set as-path prepend 1 ! route-map EX13 permit 30 match as-path 1 set as-path prepend 4 5 ! route-map EX13 deny 40 Explain the effects of route map EX13. |
| A: | Term 10 of the route map matches prefix 172.16.1.0 and prepends 2 to the AS_PATH. As a result, routers in AS 2 will reject the prefix. Term 20 matches prefix 172.16.2.0 and prepends 1 to the AS_PATH, so the route is rejected by routers in AS 1. Term 30 matches routes that have an AS_PATH of [1, 2], meaning routes that are originated in AS 2 and have been advertised by AS 1. That term prepends 4 and 5 to the AS_PATH of these routes, so they are rejected by AS 4 and AS 5. Term 40 suppresses the advertisement of any other routes. |
| 14: | Router R1 in Figure 3-36 is a route reflector for routers R2, R3, and R4 and is connected to those neighbors via Frame Relay PVCs. Write a BGP configuration for R1 that provides full connectivity for the networks attached to the four routers. The cluster ID is 6500. Figure 3-36. The Route Reflection Cluster for Configuration Exercise 14  |
| A: | [click here] router bgp 6500 no synchronization bgp cluster-id 6500 network 172.20.0.0 neighbor 172.16.1.1 remote-as 6500 neighbor 172.16.1.1 route-reflector-client neighbor 172.16.1.2 remote-as 6500 neighbor 172.16.1.2 route-reflector-client neighbor 172.16.1.3 remote-as 6500 neighbor 172.16.1.3 route-reflector-client |
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