Cisco Study notes

Catalogue

1. Routing

1.1 Static Routes

1.2 Dynamic routing

1. Routing

1.1 Static Routes

Characteristics of static Routes:

• Non-advertised lines. Static routes are private by default and are not advertised to other routers
• Relay sex. If the number of hops in the middle of a static route is greater than1(That is, the entire route path has experienced3 or more router nodes), you must configure a static route that reaches the same destination node or network on a router other than the last router

PC1 to ping the PC2, the following four static routes must be configured (two forward, two backhaul):

1) Configure a forward static route to PC2 on the R1 router (PC2 10.16.4.0/24 as the destination node with the C node IP address 10.16.2.2/24 as the next hop address)

2) Configure a forward static route to the PC2 on the R2 router (same as PC2 10.16.4.0/24 as the destination node with the e-node IP address 10.16.3.2/24 as the next-hop address)

3) Configure the backhaul static route to PC1 on the R3 router (PC1 10.16.1.1/24 as the destination node with the D-node IP address 10.16.3.1/24 as the next-hop address) to provide a route path to ping traffic backhaul ICMP messages

4) Configure a forward static route to the PC2 on the R2 router (same as PC2 10.16.4.0/24 as the destination node, with the B-node IP address 10.16.2.1/24 as the next-hop address)

Each network directly connected on each port of the router is directly interconnected, because there is a direct-connect route between them, which means that the number of hops between each network connected to the same router is 0.

• Recursion. The next hop in a static route is any of the other routers in the path, as long as the next hop is guaranteed to arrive. For example, to configure static routes to 10.16.4.0/24 that are connected to R3 on R1, the next hop can be any of the C, D, E, F interfaces

Static route configuration commands:

IP route [destination_network] [mask] [next-hop_address or Exit_interface] [administrative_distance] [Permanent]

IP route 172.16.3.0 255.255.255.0 192.168.2.4 150

IP Route 172.16.3.0 255.255.255.0 s0/0/0

IP route 0.0.0.0 0.0.0.0 10.1.5.1//configure 10.1.5.1 as default route

Whether a route will appear in the routing table depends on whether the router can communicate with the configured next-hop address. The permanent parameter guarantees that the route always exists in the routing table.

Configure the default route. If the router is configured with IGP, the route configured via IP default-network is advertised to the neighboring router.

1. IP route 0.0.0.0 0.0.0.0 interface or IP address
2. IP default-network IP Address

1.2 Dynamic routing

Dynamic Routing Features:

1. Automatic notification
2. Automatic generation of bidirectional routes
3. Only route table entries can be generated between networks and cannot generate dynamic routing table entries that reach specific nodes or hosts

Ways to prevent routing loops

1. The maximum hop count. RIP has a maximum hop count of 16
2. Split horizontally. Disables routing protocol callback route selection information. The routing protocol needs to determine which interface the routing information is received from, and once the interface is determined, the protocol can no longer issue information about the same way from the same interface.
3. Route poisoning. Identifies the unreachable network in the routing information.
4. Remain closed. Specify the re-recovery license time for a closed route or specify the time to wait for an unstable network to modify to the next best route

RIP Routing protocol

1. Routing update timer. The time interval (typically 30s) that the router sends its own routing table to neighboring routers.
2. Routing failure timer. The router eventually determines the length of the wait (typically 180s) before a route is routed to an invalid route.
3. Maintain the fail timer. Time that the route is not valid (default 180s).
4. Route Refresh timer. The time interval (default 240s) in which a route is identified as an invalid route to be removed from the routing table.

Cisco Study notes