It is related with destination nat.

1. Destination NAT
ABC
www.abc.com
Server host - 2 Server - Sw- LB-FW (Internet)--- User
L3 Virtual server  pool (2 server) 10.1.1.1 10.1.1.2
Virtual server  10.1.1.10
100.1.1.50 (physical interface)
100.1.1.1 100.1.1.10 100.1.1.20
Source Before translation. Destination After transaltion. Destination
Fw  NAT - any user - 100.1.1.1 orignal 10.1.1.10
Firewall
Any 100.1.1.1 tcp 443
Proxy ARP
Static NAT
Server  internet - (source nat ) static source destination nat but one at a time.
Dual NAT  source and destination single flow - routing bypass
Dual NAT, U turn, hair pinning
Sw1(pc1) pc2 pc3 pc4 pc5
Vlan (use) broadcast domain break
Hub  always broadcast (layer1)
Sw1 Van1 pc1 10.1.1.1 sw2 valn 2 pc2 20.1.1.2
Trunk  to allow multiple vlan traffic

2. Intervlan routing -- trunk SVI
Spanning tree
Port channel - Port aggregration  lacp pagp mode
Proxy id - (encryption domain)
ESP - New header IPSEC peer ip address
100.1.1.1 200.1.1.1
Vpn  nat
NAT-T NAT-D
NAT Discovery
Source ip destination ip hash1 hash2
Hash1 hash2
NAT D
NAT T udp 4500
Esp || udp 4500 port
NAT udp 500
Routing  l3 – destination iprouting table exit interface
Cisco
Source ip and destination ip
Routing table
Packet tracer -
Tcpdump
Curl 

3. 10.1.1.4/30
Subnet mask valid host network ip broadcast ip
No of borrowed bit Block size
1 128
2 64
3 32
4 16
5 8
6 4
7 2
Closest to the class full subnet
10.1.1.0 10.1.1.4
10.1.1.1 10.1.1.2
255.255.255.252
10.1.1.23/29 Valid ip
255.255.255.248
10.1.1.0 10.1.1.7
10.1.1.8 10.1.1.15
10.1.1.16 10.1.1.23
10.1.1.17 10.1.1.22