After configuring NAPT, it is found that some internal network addresses can always ping the external network, while others cannot. The possible reasons are ______.

Two MSR routers are connected via Ethernet and serial interfaces respectively, as shown in the figure. The PPP link layer protocol is running on the serial link, and OSPF is running on the two routers, and both belong to Area 0. At the same time, the three network segments on each router (GE interface network segment) are published in Area 0 through the network command. , Serial interface network segment, LAN network segment);
At present, the OSPF neighbors on both ends are stable, so ______. (Multiple choice)

A network connection is like:
HostA----GE0/0--MSR-1--S1/0---------S1/0--MSR-2--GE0/0----HostB
Two of the MSR routers MSR-1 and MSR-2 are interconnected back-to-back through their S1/0 interfaces, and their GE0/0 interfaces are respectively connected to the client hosts HostA and HostB. By configuring the IP address and routing, HostA can communicate with HostB in the current network. The IP address of HostA is 192.168.0.2/24, and the default gateway is 192.168.0.1. The GE0/0 interface address of MSR-1 is 192.168.0.1/24.
The following configuration has been added to MSR-1:
firewall enable
firewall default permit
acl number 3003
rule 0 deny icmp source 192.168.0.2 0 icmp-type echo-reply
interface GigabitEthernet0/0
firewall packet-filter 3003 inbound
So ______ . (Multiple choice)

To set a subnet mask so that 192.168.0.78 and 192.168.0.94 are in the same network segment, the subnet mask used cannot be ______.

If you want to check which VLANs currently exist on the switch, which one of the following commands is required?