Company XZ required to build its network according to a modular enterprise network architecture. XZ Company has 1 R&D base in Shenzhen and Xi'an each; one office building in Beijing and Shanghai; offices with more than 50 people in 23 provincial capital cities; small offices with no more than 8 people in 200 small and medium-sized cities; More than 200 marketing and technical staff are typically traveling at any one time. Due to environmental and cost problems, some offices cannot connect to the headquarters through dedicated lines or packet-switched WAN connections. According to these circumstances, the network module that XZ company should have is ________.

In the network shown in the figure, the BGP routing learning between routers is normal, and the BGP routing attributes all take default values.
After the route 9.0.0.0 is imported into BGP on RTD, if the next hop of route 9.0.0.0 on RTA is to point to RTC, the following adjustment methods are feasible: ______

In the IS-IS network shown in the figure, each router is configured as follows.
RTA-isis-1] cost-ste wide
RTB-isis-1] cost-ste wide-compatible
RTC-isis-1]cost-ste narrow-compatible
Then it is ________ that can correctly calculate the link cost between each other.

B As shown in the figure, RTA, RTB, and RTC run OSPF, and the process number is 100; RTA, RTB, and RTD run OSPF process 200. The cost of all interconnected links is set to 10. Set the external route priority of OSPF 100 to 190 on RTA and RTB, and import an external route 172.16.1.0/24 to OSPF100 on RTC. Both RTA and RTB are set to import routes from OSPF100 to OSPF200.
According to the above scenario analysis, the following description about RTD learning external route 172.16.1.0/24 is correct ______.

In the IS-IS network shown in the figure, after the routes of each router are stable, the RTC learns ______ IS-IS Level-1 routes through neighbors.