Routers and routin

1.ARP protocol (address resolution protocol): known IP resolution MAC;RARP (inverse address resolution protocol): known MAC resolution IP

1) broadcast: "one-to-many" communications

2) Multicast: "one-to-many" communication, but only for a specific scope (scope)

3) Unicast: "one-to-one" communication

Note: unicast is the result of broadcast or multicast

two。 Broadcast domain: the range that can receive the same broadcast

3.IP broadcast address: the host part is all 1

Class A: network part + host part

10.12.12.34/8 255.0.0.0

10.0.0.0 10.255.255.255

Class B: network part + network part + host part + host part

172.17.45.34/16 255.255.0.0

172.17.0.0 172.17.255.255

Class C: network part + host part

192.168.1.100/24 255.255.255.0

192.168.1.0 192.168.1.255

4.MAC broadcast address: FF-FF-FF-FF-FF-FF

5.ARP principle

1) check the ARP cache table

2) send ARP broadcast

3) the switch receives a broadcast and broadcasts all ports except the sending port

4) ARP reply, and the receiver responds to its own MAC address and caches the sent IP and MAC

5) the sender caches the receiver's response to MAC and IP

Aging time: clear the ARP cache table within 120s or restart the system, or manually using arp-d

Windows ARP command

1) arp-a / / View arp cache table

2) arp-d / / manually clear the ARP cache table

3) arp-s IP MAC / / static binding MAC

Cisco ARP command

1) in show arp / / privileged mode, view the arp cache table

2) clear the arp cache table in clear arp-cache / / global configuration mode

3) bind ARP statically in arp IP MAC arpa / / global configuration mode

II. Routers

1. "look up the table (routing table) forwarding"

two。 Router formation

1) directly connected routing: router ports are configured with IP automatic generation

2) non-directly connected routes: manually configured by the administrator

3. Route classification

1) static route: manually configured by administrator, unidirectional

2) dynamic routing: OSPF, RIP, etc., which automatically learn all routing information in the current network.

3) default route: a special static route that reduces routing entries and is generally used in stub areas

Note: router has one interface and one network segment.

4.Cisco Router configuration Command

1) Router (config-if) # ip addr IP subnet mask / / configure an IP address for the specified interface

2) Router (config-if) # no sh / / enable the specified interface (sh shuts down the interface)

3) Router (config) # ip route destination subnet mask interface / / configure static route

4) Router (config) # ip route 0.0.0.0 0.0.0.0 interface / / configure a default route

Note: the default route is used only when the router has only one exit, and pay attention to the routing loop