Static Route Flashcards
What is the difference between connected routers and local routers?
The terms “connected routers” and “local routers” are not standard networking terminology but can be interpreted based on context. Here’s a breakdown of how these terms might be used:
- Connected Routers
• Definition: Routers that are directly connected to each other via a physical or logical link.
• Key Characteristics:
• Share a direct network segment (e.g., Ethernet, serial, or fiber link).
• Can communicate without requiring an intermediate router.
• Exchange routing information via dynamic routing protocols (e.g., OSPF, EIGRP, BGP) or static routes.
• Example:
• Router A (192.168.1.1/24) is directly connected to Router B (192.168.1.2/24) via a physical interface.
• They can exchange traffic without needing another router. - Local Routers
• Possible Meanings:- A router within the local network (e.g., an enterprise or home router managing internal traffic).
- A router managing local subnets (e.g., a gateway router that connects an internal network to an external network).
• Example:
• A router inside a company’s LAN that routes traffic between VLANs or subnets is considered a “local router.”
• A home router managing Wi-Fi and wired connections within a house is also a “local router.”
Key Difference:
• Connected routers refer to routers that have a direct physical or logical connection.
• Local routers typically refer to routers within a specific network, managing local traffic rather than acting as a backbone or external gateway.
What are router functions?
• A router has two main functions:
• Determining the best path to available networks
• Forwarding traffic to those networks
The routing table:
• The best available path or paths to a destination network are listed in a router’s routing table and will be used for forwarding traffic
• A routing table consists of directly connected networks and routes configured statically by the administrator or dynamically learned through a routing protocol.
What is a static route?
• If a router receives traffic for a network which it is not directly attached to, it needs to know how to get there in order to forward the traffic
• An administrator can manually add a static route to the destination, or the router can learn it via a routing protocol
ip route 10.0.1.0 255.255.255.0 10.0.0.1
ip route 10.0.2.0 255.255.255.0 10.0.0.1
ip route 10.1.0.0 255.255.255.0 10.0.0.2
A static route is a manually configured route in a network that defines a specific path for traffic to reach a destination. Unlike dynamic routing, which relies on protocols to automatically adjust routes based on network changes, static routes require manual updates if the network topology changes.
Key Features of Static Routes:
• Manually Configured: Network administrators specify the next-hop IP address or exit interface.
• Fixed Path: Traffic always follows the predefined route unless manually changed.
• Simple and Efficient: No additional CPU or memory usage for route calculations.
• No Automatic Failover: If the specified route fails, traffic cannot be rerouted unless an alternative route is manually configured.
When to Use Static Routes:
• When network topology is simple.
• For default routes (e.g., forwarding all unknown traffic to a specific gateway).
• When security is a priority, avoiding dynamic protocol vulnerabilities.
• In small networks where dynamic routing is unnecessary.
Show ip route table command
sh ip route
What is summary route ?
• For static routing, summary routes lessen administrative overhead and memory usage on the routers
Summarisation doesn’t have to be on classful boundaries
To summarise the range 10.1.0.0 to 10.1.3.0:
• route 10.1.0.0 255.255.252.0 10.0.0.2
Summary Route (Route Aggregation)
• Imagine there are two networks: 192.168.1.0/24 and 192.168.2.0/24.
• Instead of having separate entries for each, we combine them into one broader summary route: 192.168.0.0/22.
What is Longest prefix match?
Longest Prefix Match (LPM)
• Imagine you have two maps: one of a whole country and another of a single city.
• If you want directions to a street, you use the city map because it is more detailed.
• Similarly, the router picks the most specific route when multiple routes match a destination.
Suppose a router has two routes:
• 192.168.1.0/24 (specific)
• 192.168.0.0/16 (general)
• A packet arrives for 192.168.1.10.
• The router checks both routes and picks 192.168.1.0/24 because it is more specific (has a longer prefix).
What is Load Balancing?
• The router has two equal-cost paths to 192.168.3.0/24.
• Instead of using only one, it distributes traffic between both paths.
• This helps in balancing network load and preventing congestion.
Imagine you have two roads leading to the same place.
• If both roads take the same time, you use both to send traffic.
• A router does the same: if it has two equal paths, it splits the traffic between them.
What is default route or getaway of last resort?
ip route 0.0.0.0 0.0.0.0. Getaway adresss
If a router doesn’t have a specific route for a destination, it sends the packet to the default route (0.0.0.0/0).
• This is useful for sending unknown traffic (e.g., internet traffic) to a gateway.
Think of this as asking someone for help when you don’t know the way.
• If the router doesn’t have a specific route, it sends the packet to a default route (like sending all unknown letters to the main post office).
