Internet dual-link implementation of "original route back"

As shown in a recent project in Guangzhou, this topology applies for Internet links from China Telecom and China Unicom to connect to different routers respectively. The vro is Cisco 3925, and the switch is Cisco 3560V2.
Requirement: if an access request is initiated from the Internet into the local area, the original route is required to return to the original route. That is, if the request is sent from the telecom link, the request is returned from the telecom link.
Analysis:
Select the core node of the route entry on the switch.
There are two ways to achieve the above requirements.
1. Use BGP. Configure BGP on the two routers to receive BGP Route entries of China Telecom and China Unicom respectively. This not only enables the original route back when the access is initiated from the Internet, it also selects the best choice when the Intranet actively accesses the Internet, that is, the access to the telecommunications IP from the telecommunications link, access to the unicom ip from the UNICOM link. The disadvantage is that the equipment is demanding, and the vrociscisco3925 should be supported, but the cisco 3560V2 won't work.
2. Use NAT. You can use the NAT Function to convert the source IP address that is actively accessed from the Internet to a specific IP address.
In this project, 10.0.0.0/8 is divided into two CIDR blocks: 10.127.0.0/255.128.0.0 and 10.128.0.0/255.128.0.0. The two CIDR blocks are divided into more than 8.3 million IP addresses.
You can only use NAT ing because you cannot use PAT to initiate access from the Internet. Each session that initiates an access from the Internet corresponds to a specific IP address, which can have more than 8.3 million sessions. An Internet user may have multiple sessions, which may occupy multiple specific IP addresses. In this project, the number of more than 8.3 million sessions is sufficient.
China Unicom Route_L Configuration:
Router ospf 1
Log-adjacency-changes
Redistribute connected subnets
Network 192.168.35.0 0.0.0.255 area 0
Default-information originate always route-map
!
Ip nat pool 10 10.0.0.1 10.127.255.254 netmask 255.128.0.0 \ Internet access Source IP Address Translation pool, more than 8 million.
Ip nat inside source list 2 interface FastEthernet0/0 overload
Ip nat outside source list 2 pool 10 \ Internet access nat
 
Access-list 2 permit any
!
Route-map a permit 10
Set metric 2
 
China Telecom Route_D Configuration:
Router ospf 100
Log-adjacency-changes
Redistribute connected subnets
Network 192.168.45.0 0.0.0.255 area 0
Default-information originate always
!
Ip nat pool 10 10.128.0.1 10.128.255.254 netmask 255.128.0.0 \ Internet access Source IP Address Translation pool, a total of more than 8 million.
Ip nat inside source list 2 interface FastEthernet0/0 overload
Ip nat outside source list 2 pool 10 \ Internet access nat
!
Access-list 2 permit any
 
Switch configuration
Router ospf 100
Log-adjacency-changes
Network 192.168.35.0 0.0.0.255 area 0
Network 192.168.45.0 0.0.0.255 area 0
!
Ip route 10.127.0.0 255.128.0.0 192.168.35.3 Static Routing for a specific address pool
Ip route 10.128.0.0 255.128.0.0 192.168.45.3 Static Routing for a specific address pool

Author: "Xia ke"