As shown in the figure, a sham link is established between PE1 and PE2 through the LoopBackD interface. CE2 can learn the route to the 192.168.1.0/24 network segment (the direct route on CE1) through the sham link and backdoor link. If you keep the default configuration, the cost value of the route from CE2 to the 192.168.1.0/24 network segment should be (). (Please fill in the Arabic numerals directly, without symbols)

In an operator's MPLSVPN network, there are two devices PE1 and PE2 for MPLSVPN data forwarding. PE1 receives a private network route of 172.16.1.0/24 from the client, and converts it to a VPNv4 route on PE1 and assigns a label of 1027 Released to PE2. The outgoing label of the MPLS LSR-ID of PE2 reaching PE1 is 1025o When a client on PE2 accesses 172.16.1.0/24, the frame sent by PE2, the inner and outer labels should be a combination of the following 6 options?

As shown in the figure:

As shown below:

In a multi-level RR scenario, a large number of second-level RR are connected to the first-level RR, which may cause the BGP routing table of the first-level RR to overflow. What method can be used to reduce the risk of overflow of the BGP routing table of the first-level RR?