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CCIE Professional Development Large-Scale IP Network Solut phần 10

mỗi khu vực sẽ thích sử dụng kết nối riêng của mình với Internet. Giải quyết đúng và mạng lưới khu vực hóa sẽ cải thiện định tuyến không đối xứng, mặc dù nó sẽ không thể tránh được hoàn toàn. Alpha.com cuộc đàm phán ISP1 và gửi cho nó một con đường cụ thể hơn từ cả Bắc Mỹ và châu Âu. | Each region has its own ISP connection obviously each region would prefer to use its own connection to the Internet. Proper addressing and network regionalization will improve asymmetric routing although it will not be avoided completely. Alpha.com talks to ISP1 and sends it a more specific route from both North America and Europe. The routes sent from North America and Europe are shown in Figure 16-20. Alpha.com also can send a less-specific route in case of failure. This way Alpha.com does not need to send an MED to ISP1. This is a sensitive issue however because most of the ISPs would not accept subnet routes from their customers. If ISP1 accepts the routes it must keep the subnet routes in its table and share this information with ISP2 so that ISP2 also performs optimal routing. Both the ISPs will advertise only 172.16.0.0 16 to the rest of the Internet. The configuration for C1 peering in the United States with ISP1 would be the following router bgp 109 neighbor 140.10.1.1 remote-as 2 neighbor 140.10.1.1 remove-private-AS neighbor 140.10.1.1 route-map set-community in neighbor 140.10.1.1 send-community neighbor 172.16.252.11 remote-as 109 neighbor 172.16.252.12 remote-as 109 neighbor 172.16.252.13 remote-as 109 neighbor 172.16.252.14 remote-as 109 neighbor 172.16.252.15 remote-as 109 network 172.16.0.0 mask 255.255.192.0 network 172.16.64.0 mask 255.255.224.0 network 172.16.0.0 route-map set-community permit 10 match ip address 1 set community 109 70 443 route-map set-community permit 20 match ip address 2 access-lj st 1 permit 198.10.1.0 0.0.0.255 access-lj st 1 permit 198.10.2.0 0.0.0.255 access-lj st 1 permit 198.10.3.0 0.0.0.255 access-lj st 2 permit any This router will advertise three routes to its EBGP neighbor. The first two networks with mask statements advertise a more specific route to its EBGP peers that cover the North America range. The less-specific route with the network statement covers all other networks for Europe and Asia. This network .