diff --git a/11. Static Routing.md b/11. Static Routing.md index 76e599e..2d32d80 100644 --- a/11. Static Routing.md +++ b/11. Static Routing.md @@ -2,10 +2,13 @@ id: 1777544578-NSAK aliases: - Static Routing -tags: [] +tags: + - CCNA + - Router --- # Static Routing + ## Network diagram ![Diagram](./Images/Diagram_Static_routing.png) @@ -15,10 +18,219 @@ tags: [] End hists like PC1 and PC4 can send packets directly to destinations in their connected network. - PC1 is connected to 192.168.1.0/24, PC4 is connected to 192.168.4.0/24 +To send packets to destinations outside of their local network, they must send the packets to their default gateway. + +```PC1 (linux Config) +iface eth0 inet static + address 192.168.1.10/24 + gateway 192.168.1.1 +``` + +```PC4 (linux Config) +iface eth0 inet static + address 192.168.4.10/24 + gateway 192.168.4.4 +``` + +The default gateway configuration is also called a default route. +- It is a route to 0.0.0.0/0 = all netmask bits set to 0. Includes all addresses 0.0.0.0 -> 255.255.255.255 + + The default route is the least specific route possible, because it includes all [[IP addresses]]. + 0.0.0.0 = 4,294,967,296 IP addresses + A /32 route (ie. Local route) is the most specific route possible, because it specifies only one IP address + 192.168.1.1/32 = 1 IP address + +End hosts usually have no need for any more specific routes. + +- They just need to know: to send packets outside of my local network, I should send them to my default gateway + - Src. IP: 192.168.1.10 + - Dst. IP: 192.168.4.10 + - Dst. MAC = R1 G0/2 MAC + - Src. MAC = PC1 eth0 MAC + - to learn R1 G0/2's MAC address, PC1 will first send an [[ARP]] request to 192.168.1.1 + +- When R1 Receives the frame from PC1, it will de-encapsulate it (remove L2 header/ trailer) and look at the inside packet. + +- It will check the routing table for the most-specific matching route: + +- R1 has no matching routes in irs routing table. + - It will drop the packet. + +- To properly forward the packet, R1 needs a route to the destination network (192.168.4.0/24) + - Routes are instructions: to send a packet to destinations in network 192.168.4.0/24, forward the packet to next hop Y + +- There are two possible path packets from PC1 to PC4 can take: + 1) PC1 -> R1 -> R3 -> R4 -> PC4 + 2) PC1 -> R1 -> R2 -> R4 -> PC4 + + - (it will be learn later) + +## Static Route configuration + +Each router in the path needs two routes: a route to 192.168.1.0/24 and a route to 192.168.4.0/24. + - this ensures two-way reachability (PC1 can send packets to PC4, PC4 can send packets to PC1). + + routers don't need routes to all networks in the path to the destination. + - R1 doesn't need a route to 192.168.34.0/24. + - R4 doesn't need a route to 192.168.13.0/24. + +- R1 already has a **Connected route** to 192.168.1.0/24 +- R4 already has a **Connected route** to 192.168.4.0/24 + - The other routes must be manually configured (using **Static Routes**) + +### Static Route Chart + + | Router | Destination | Next-Hop | + | ------ | -------------- | -------------- | + | R1 | 192.168.1.0/24 | Connected | + | R1 | 192.168.4.0/24 | 192.168.13.3 | + | R3 | 192.168.1.0/24 | 192.168.13.1 | + | R3 | 192.168.4.0/24 | 192.168.34.4 | + | R4 | 192.168.1.0/24 | 192.168.34.3 | + | R4 | 192.168.4.0/24 | Connected | + + +### R1 Configuration + +For configuring Static route the command is: + + ```Cisco +R1(config)# ip route ip-address netmask next-hop +``` + +so for R1: + + ```Cisco +R1(config)# ip route 192.168.4.0 255.255.255.0 192.168.13.3 +``` + +To check the routes + + ```Cisco +R1(config)# do show ip route + +Codes: L - local, C - connected, S - static .... + +//partial return + +192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks +C 192.168.1.0/24 is directly connected, GigabitEthernet0/2 +L 192.168.1.1/32 is directly connected, GigabitEthernet0/2 +S 192.168.4.0/24 [1/0] via 192.168.13.3 +``` + + The [1/0] displayed in static routes means: + [adminstrative Distance/Metric] + We will cover these concepts later in the course. + +so for R3: + + ```Cisco +R3(config)# ip route 192.168.1.0 255.255.255.0 192.168.13.1 +// to send packets to 192.168.1.0/ 24 send packets to R1 +R3(config)# ip route 192.168.4.0 255.255.255.0 192.168.34.4 +// to send packets to 192.168.4.0/ 24 send packets to R4 +``` + +so for R4: + + ```Cisco +R4(config)# ip route 192.168.1.0 255.255.255.0 192.168.34.3 +``` + +### Test connection + +Now to see if *PC1* and *PC4* can communicate + + +```powershell +PC1:$ ping 192.168.4.10 +5 packets transmitted, 5 packets received, 0% packet loss +``` + +If the ping is successful, that means there is two-way reachability. +*PC1* can reach *PC4*, and *PC4* can reach *PC1* + +## Static Route Configuration with exit-interface + +instead of configuring a next hop we can configure an exit interface +instead of the ip address we can specify the interface + +We will do this for R2: + + ```Cisco +R2(config)# ip route ip-address netmask exit-interface +R2(config)# ip route 192.168.1.0 255.255.255.0 g0/0 +``` + +but we can do both exit-interface and next-hop + + ```Cisco +R2(config)# ip route ip-address netmask exit-interface next-hop +R2(config)# ip route 192.168.4.0 255.255.255.0 g0/1 192.168.24.4 +``` + +so it returns + + ```Cisco +R2(config)# do show ip route + +// exit interface +S 192.168.1.0/24 is directly connected, GigabitEthernet0/0 + +// exit interface and next-hop +S 192.168.4.0/24 [1/0] via 192.168.24.4, GigabitEthernet0/1 +``` + +- Static routes in which you specify only the exit-interface rely on a feature called Proxy ARP to function +- This is usually not a problem, but generally you can stick to + - next-hop or exit-interface next-hop +- Neither is 'better' than the other: use which you prefer. + +## Default route + +- A default route is a route to 0.0.0.0/0 + - 0.0.0.0/0 is the least specific route possible; it includes every possible destination IP address. +- if the router doesn't have any more specific routes that match a packet's destination IP address, the router + will forward the packet using the default route. +- A default route is often used to direct traffic to the [[Internet]]. + +- Example for a internal corporate network.: + - More specific routes are used for destinations in the internal corporate network. + - Traffic to destinations outside of the internal network is sent to the internet. + +!(default route)[./Images/default_routes.png] + +### configure default route + +```Cisco +R1# show ip route +Gateway of last resort is not set +``` + +No default route has been configured yet +To configure a default route use this command + +```Cisco +R1(config)# ip route 0.0.0.0 0.0.0.0 203.0.113.2 + +//check +R1(config)# do show ip route +* - candidate default + +S* 0.0.0.0/0 [1/0] via 203.0.113.2 +``` + ## Review - Connected and Local routes [[Routing Fundamentals]] - Intro to Static Routes - Static Route configuration + +```Cisco +R2(config)# ip route ip-address netmask next-hop +R2(config)# ip route ip-address netmask exit-interface +R2(config)# ip route ip-address netmask exit-interface next-hop +``` - Default Routes diff --git a/Images/default_routes.png b/Images/default_routes.png new file mode 100644 index 0000000..f4938d0 Binary files /dev/null and b/Images/default_routes.png differ