<Jeremy's IT Lab> Day11: Routing Fundamentals, Static Route

★ Routing Fundamentals, Static Route

 

Switch: Mac address table

Router: Routing table

 

• Connected and Local routes
• Static Routing

 

Routing is the process routers use to determine the path that IP packets should take over a NW to reach their destin.

-> Routers store routes to all of their known destin in a routing table

-> when routers receive packets, look in routing table

- Dynamic routing: Daynamic routing protocols (OSPF) automatically bulid their routing tables

- Static routing: manually congifures routes on the router

 

- route tells the routher to send to destin X, you should sen the pakcet to next-hop(next router in the path to the destin)

-> or if directly connected to the router(Connected route), send directly to destin

-> or if it is own IP(Local route), receive packet for yourself

 

WAN: Wide Area Network

-> a nw that extends over a large geographical area

 

//CLI

Routing Table

R1# show ip route

-> Codes legend(범례) in the output of show ip route lists which routers can use

-> L - Local route: actual IP adrs configured on the interface(with /32 netmask)

## if IP is 192.168.1.1/24, route will be to 192.168.1.0/24

-> C - Connected route: route to the NW the interface is connected to (with actual netmask configured on inter)

## if IP is 192.168.1.1/24, route will be to 192.168.1.0/32

-> When configure IP adrs with no shutdown, routes will automatically be added to routing table(L C)

-> A route matched a destination if the packet's destin IP adrs is part of the NW specified in the route.

-> If packet doensn't have a match the packet's destin, router will drop the packet. (!= switch, flood frames)

-> Use the most specific matching route to forward the packet. (!= switch, exact same MAC)

 

 

 

 

 

https://www.youtube.com/watch?v=YCv4-_sMvYE&list=PLxbwE86jKRgMpuZuLBivzlM8s2Dk5lXBQ&index=20

Static Route configuration:

-> Two-way reachability (PC1 can send packets to PC4, and opposite is possible)

-> manually configured (using Static routes)

-> To allow PC1 and PC4 to communicate with over the NW, configure Static routes on R1, R3, and R4

(if we consider only R1- R3 - R4 route)

 

//CLI

R1(config)# ip route destin-ip-address netmask next-hop

## R1(config)# ip route 192.168.4.0 255.255.255.0 192.168.13.3

## >> S     192.168.4.0/24 [1/0] via 192.168.13.3

* [1/0] = [Administrative Distance/Metric]

 

R2(config)# ip route ip-adrs netmask exit-interface

## R2(config)# ip route 192.168.1.0 255.255.255.0 g0/0

## >> Direcly conntected

R2(config)# ip route ip-adrs netmask exit-interface next-hop

## R2(config)# ip route 192.168.4.0 255.255.255.0 g0/0 192.168.24.4

## >> S     192.168.4.0/24 [1/0] via 192.168.24.4

 

-> Static routes having only exit-interface rely on a feature called Proxy ARP to function

-> Neither is 'better' than other

 

Default route(default gatway):

-> 0.0.0.0/0 (least specific route; includes every destin IP)

-> If router doesn't have any more specifics, the router will forward the packet using default route

-> Used to direct traffic to the Internet

* More specific routes are used for destin in internal corporate network(Router)

* Traffic to destins outside of the internal NW is sent to the Internet

 

##>> * - candiate default 

 

 

Q1. IP address configured on a router interface will appeare in the routing table as what kinds of route?

>Local

 

Q2. congifure a default route on a Cisco router?

> R1(config)# ip route 0.0.0.0 0.0.0.0 10.1.1.255 (cannot specify prefix length with '/')

 

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Acronym:

• WAN: Wide Area Network