In the IS-IS network as shown in the figure, RTA and RTB are configured as follows:
RTA]isis
RTA-isis-1]network-entit01.1111.1111.1111.00
RTA-isis-1]interface serial 2/0
RTA-Serial2/0]isis enable 1
RTB]isis 2
RTB-isis-2]network-entit01.2222.2222.2222.00
RTB-isis-2]interface serial 1/0
RTB-Serial1/0]isis enable 2
RTB-Serial1/0]isis circuit-level level-2
Then between RTA and RTB ______

In the topology shown in the figure, the following configurations are performed on RTA and RTB respectively:
RTA]ospf 1
RTA-ospf-1]area 1
RTA-ospf-1-area-0.0.0.1]network 1.1.1.1 0.0.0.0
RTA-ospf-1-area-0.0.0.1]network 10.0.0.0 0.0.0.255
RTA-ospf-1-area-0.0.0.1]network 192.168.1.0 0.0.0.255
RTA-ospf-1-area-0.0.0.1]network 192.168.4.0 0.0.0.255
RTA-ospf-1-area-0.0.0.1]network 192.168.7.0 0.0.0.127
RTA-ospf-1-area-0.0.0.1]network 192.168.8.0 0.0.0.127
RTA-ospf-1-area-0.0.0.1]network 192.168.15.0 0.0.0.255
RTB]ospf 1
RTB-ospf-1]area 1
RTB-ospf-1-area-0.0.0.1]network 10.0.0.0 0.0.0.255
RTB-ospf-1-area-0.0.0.1]area 0
RTB-ospf-1-area-0.0.0.1]abr-summar192.168.0.0 255.255.252.0 not-advertise
Then which of the following routes may exist in the RTC routing table_____

In the IS-IS network as shown in the figure, after the routes of each router are stable, there are ______ IS-IS Level-2 routes learned by RTA through neighbors.

The advantages of the hierarchical network model include _______. (Choose one or more)

Among the following routing protocols, _______ supports manual route aggregation. (Choose one or more)