IP Connectivity
2024, September 9
0. IP Connectivity
IP Connectivity refers to the ability of devices to communicate with each other using the Internet Protocol (IP) across a network. It forms the foundation of modern networking, enabling data exchange between devices, whether they are on the same local network (LAN) or across geographically distributed networks (WAN). IP connectivity relies on routers, switches, and routing protocols to efficiently deliver packets from a source to a destination, regardless of the devices' locations.
0.1 Components of IP Connectivity
Several key components are essential for ensuring proper IP connectivity:
- IP Addressing: Every device on a network is assigned a unique IP address, which acts as an identifier for sending and receiving data. IP addresses are categorized as either IPv4 or IPv6.
- Routing: Routers are responsible for determining the best path for data to travel between networks. They use routing tables and protocols to forward packets towards their destination.
- Subnetting: Subnets divide larger networks into smaller, manageable segments, improving efficiency and security. A subnet mask is used to differentiate between the network and host portions of an IP address.
- Default Gateway: The default gateway is a router that acts as an access point to external networks. Devices send traffic to the default gateway if the destination IP is outside the local network.
0.2 The Role of the Internet Protocol (IP)
The Internet Protocol (IP) is a set of rules governing how data is transmitted over a network. It defines how data packets are formatted, addressed, transmitted, and routed to the correct destination. The primary responsibilities of IP include:
- Packetizing Data: IP breaks data into smaller packets to be transmitted across the network.
- Addressing: IP assigns source and destination addresses to each packet to ensure it reaches the correct endpoint.
- Routing: Routers use IP addresses to forward packets along the most efficient path toward their destination.
- Fragmentation and Reassembly: Large packets may be fragmented to accommodate network limitations and then reassembled at the destination.
0.3 Types of IP Addresses
IP addresses are crucial for identifying devices and routing traffic. There are two main types of IP addresses:
- IPv4 (Internet Protocol Version 4): IPv4 addresses are 32-bit addresses, typically written in decimal as four octets separated by periods (e.g., 192.168.1.1). Due to the limited number of IPv4 addresses, it is being gradually replaced by IPv6.
- IPv6 (Internet Protocol Version 6): IPv6 addresses are 128-bit addresses, written in hexadecimal and separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). IPv6 provides a much larger address space and is essential for supporting the growing number of devices on the internet.
0.4 Routing in IP Connectivity
Routing is a key aspect of IP connectivity, enabling data to travel between networks. Routers use routing tables and protocols to determine the best path for packets. There are two main types of routing:
- Static Routing: Routes are manually configured by network administrators. Static routing is simple and efficient for small networks but is not scalable for larger, dynamic networks.
- Dynamic Routing: Routers automatically update their routing tables based on the network's current state using routing protocols such as OSPF, BGP, or RIP. This allows the network to adapt to changes, such as link failures or network congestion.
0.5 Common IP Connectivity Issues
Several common issues can disrupt IP connectivity:
- IP Address Conflicts: Occurs when two devices are assigned the same IP address, causing communication problems.
- Routing Misconfigurations: Incorrect routing tables or protocols can cause data packets to take inefficient or incorrect paths.
- Network Address Translation (NAT) Issues: NAT is used to map private IP addresses to public IP addresses for internet access. Misconfigurations can block traffic.
- Subnet Mismatches: Devices in different subnets may not be able to communicate if subnet masks are misconfigured.
0.6 Importance of IP Connectivity
IP connectivity is the backbone of modern communication, enabling devices to interact seamlessly over the internet or within private networks. It underpins web browsing, email, streaming, cloud services, and countless other applications. Ensuring reliable and efficient IP connectivity is essential for maintaining network performance and functionality.
1. Interpret the Components of a Routing Table
The routing table is a vital tool used by routers and hosts to determine the best path for forwarding packets to their destination. It contains specific information about the routes available to different networks. Interpreting the components of a routing table is essential for understanding how packets are routed across a network.
1.1 Components of a Routing Table
Each entry in the routing table contains key information that helps routers make forwarding decisions. The most common components include:
- Destination Network: This field specifies the network address for which the route is valid. It identifies the range of IP addresses that can be reached using the particular route.
- Subnet Mask: Defines the portion of the destination network address that is used to identify the network. The subnet mask helps differentiate the network part of an IP address from the host part.
- Next Hop: Indicates the IP address of the next router or gateway to which the packet should be sent in order to reach its destination. The next hop serves as the intermediate destination.
- Metric: The metric is a numerical value representing the cost associated with the route. Lower metric values are preferred, indicating a more efficient or desirable path.
- Interface: The interface specifies the physical or logical network interface through which the packet should be sent. It tells the router where to forward the packet (e.g., Ethernet, Wi-Fi, etc.).
- Routing Protocol Code: This code indicates how the router learned about the route. Common codes include static routes and dynamic routes learned from protocols like OSPF, BGP, or RIP.
1.2 Example of a Routing Table
Below is a simple example of a routing table and its components:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
10.0.0.0 255.0.0.0 10.1.1.1 5 Ethernet1 BGP
172.16.0.0 255.255.0.0 172.16.1.2 100 Ethernet2 Static
- Destination Network: In this table, 192.168.1.0 refers to the destination network.
- Subnet Mask: The 255.255.255.0 subnet mask identifies the network portion.
- Next Hop: The packet will be forwarded to the 192.168.2.1 gateway.
- Metric: The OSPF route has a metric of 10, which is used to compare the efficiency of routes.
- Interface: The packet will leave through Ethernet0.
- Protocol: The route was learned via OSPF.
1.3 Longest Prefix Match
Routers use the Longest Prefix Match rule to select the best route when multiple routes exist for the same destination. The route with the longest matching prefix (more specific network) is preferred. For example, if two routes to the same destination exist, such as 192.168.0.0/16 and 192.168.1.0/24, the latter is more specific and will be chosen.
1.4 Importance of Routing Table Components
Each component of the routing table plays a critical role in ensuring efficient and correct packet forwarding. Misconfigured routing tables can lead to inefficient routing, packet loss, or network loops. Understanding how to interpret these components is essential for troubleshooting network issues and optimizing performance.
2. IP Connectivity - Interpret the Components of Routing Table
In IP networking, the routing table is a critical component that determines how data packets are forwarded to their destination. The routing table is stored in a router or a host, and it contains a set of rules for deciding the next hop for each IP packet. Understanding the components of a routing table is key to grasping how IP connectivity works in networks.
2.1 Components of a Routing Table
The routing table consists of several essential fields that allow for the proper routing of packets. Each row in the table typically represents one route, and these components help in determining the correct path for the packet.
- Destination Network: This specifies the network address for which the route is defined. It indicates the range of IP addresses that are reachable through this route.
- Subnet Mask: Defines the range of addresses within the destination network by specifying which part of the address is the network part and which part is the host part.
- Next Hop: Specifies the IP address of the next router or gateway through which the packet should be forwarded to reach its final destination.
- Metric: A value that represents the "cost" of using a particular route. Lower metrics are preferred, as they signify a more efficient or shorter path to the destination.
- Interface: Identifies the router's or host's interface through which the packet should be sent. It indicates which physical or logical connection should be used to reach the next hop.
- Routing Protocol Code: A symbol that represents which routing protocol was used to learn or establish the route. This can include static routes, as well as routes learned from dynamic protocols like OSPF, BGP, or RIP.
2.2 Routing Protocol Code
The routing protocol code is used to identify how the router or host learned about the particular route. These codes are essential for distinguishing between routes provided by different routing protocols and manually configured static routes. Each protocol has its own characteristics in terms of speed, reliability, and the type of network for which it is best suited. Below are common routing protocol codes used in routing tables:
- C (Connected): Directly connected network, typically associated with the device's local interfaces.
- S (Static): Static route that has been manually added by an administrator.
- R (RIP): Routes learned through the Routing Information Protocol (RIP), a distance-vector protocol.
- O (OSPF): Routes learned from the Open Shortest Path First (OSPF) protocol, a link-state protocol.
- B (BGP): Routes learned from the Border Gateway Protocol (BGP), used for routing between autonomous systems.
- D (EIGRP): Routes learned from the Enhanced Interior Gateway Routing Protocol (EIGRP), a Cisco-proprietary hybrid routing protocol.
2.3 Example of a Routing Table
To visualize how these components work together, here's an example of a simple routing table:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
10.0.0.0 255.0.0.0 10.1.1.1 5 Ethernet1 BGP
172.16.0.0 255.255.0.0 172.16.1.2 1 Ethernet2 Static
This routing table shows three routes learned from different protocols: OSPF, BGP, and Static. The router uses this table to determine the next hop and interface for each packet it receives, based on the destination IP address.
3. Prefix
A prefix in networking refers to a combination of an IP address and a subnet mask that defines a range of IP addresses. It is used to specify networks and subnets in routing tables, enabling routers to determine which IP addresses belong to which networks. The prefix plays a crucial role in IP connectivity and routing decisions, as it identifies the scope of the network or subnet.
3.1 Structure of a Prefix
A prefix is typically represented in the following format: IP address/Prefix Length. The prefix length represents the number of bits in the subnet mask that are used to identify the network portion of the address. This is crucial for routers to match IP addresses with their respective networks. For example:
- 192.168.1.0/24: This means the first 24 bits of the IP address are used for the network, and the remaining 8 bits are available for host addresses.
3.2 Subnet Mask and Prefix Length
The subnet mask is closely related to the prefix. The prefix length is simply a shorthand representation of the subnet mask. For example:
- /24 corresponds to a subnet mask of 255.255.255.0, meaning the first 24 bits are used for the network address.
- /16 corresponds to a subnet mask of 255.255.0.0, meaning the first 16 bits are used for the network address.
The prefix length determines how large the subnet is, and it directly affects the number of hosts that can exist within that subnet. A smaller prefix length (e.g., /16) means a larger subnet, while a larger prefix length (e.g., /28) means a smaller subnet.
3.3 Prefix and Routing Decisions
Routers use prefixes to make routing decisions. When a packet arrives at a router, the destination IP address is compared to the prefixes in the routing table. The router chooses the route with the longest prefix match, also known as the Longest Prefix Match (LPM) rule. The longest prefix match ensures that the most specific route is chosen for forwarding the packet.
For example, given two routes in the routing table:
- 192.168.0.0/16
- 192.168.1.0/24
If the destination IP address is 192.168.1.45, the router will choose the route with the /24 prefix, as it is more specific than the /16 prefix.
3.4 Example of Prefix Usage
Here's an example of how a prefix appears in a routing table:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0/24 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
10.0.0.0/8 255.0.0.0 10.1.1.1 5 Ethernet1 BGP
172.16.0.0/16 255.255.0.0 172.16.1.2 1 Ethernet2 Static
Each row in this routing table shows a prefix representing a destination network, followed by its corresponding subnet mask. The prefix length helps the router identify the size of the network and make proper routing decisions.
4. Network Mask
The network mask, also known as a subnet mask, is a 32-bit number used in IP networking to divide an IP address into two parts: the network portion and the host portion. It helps routers and devices determine which part of an IP address refers to the network and which part refers to the host. The network mask is crucial in defining the size of a subnet and plays a significant role in routing decisions and IP addressing.
4.1 Structure of a Network Mask
A network mask consists of two parts:
- Network Portion: The leftmost bits of the mask that are set to '1' represent the network part of the IP address.
- Host Portion: The rightmost bits of the mask that are set to '0' represent the host part of the IP address, indicating how many addresses are available for devices within the subnet.
For example, the network mask 255.255.255.0 in binary would be:
11111111.11111111.11111111.00000000
Here, the first 24 bits are the network portion, and the remaining 8 bits are for the host portion.
4.2 Common Network Masks
Here are some common subnet masks and their prefix lengths:
- 255.0.0.0 (or /8): Used for large networks, allowing over 16 million host addresses.
- 255.255.0.0 (or /16): Used for medium-sized networks, allowing up to 65,536 host addresses.
- 255.255.255.0 (or /24): Common for smaller networks, allowing 256 host addresses.
- 255.255.255.240 (or /28): Used for very small networks, allowing only 16 host addresses.
4.3 Role of the Network Mask in Routing
The network mask helps routers determine whether a destination IP address belongs to the same network or should be forwarded to another network. When a router receives a packet, it performs a bitwise AND operation between the destination IP address and the subnet mask of each route in its routing table to find the best match.
For example, consider the destination IP address 192.168.1.45 and a network mask of 255.255.255.0:
Destination IP: 192.168.1.45 -> 11000000.10101000.00000001.00101101
Subnet Mask: 255.255.255.0 -> 11111111.11111111.11111111.00000000
Result (Network ID): 192.168.1.0 -> 11000000.10101000.00000001.00000000
The result of the AND operation is the network ID 192.168.1.0, which helps the router determine whether the destination is on the same network or if it needs to forward the packet to another router.
4.4 Network Mask and Subnetting
Subnetting is the process of dividing a larger network into smaller sub-networks (subnets). The network mask is used to define the size of each subnet. By increasing the number of '1's in the mask, you can create more subnets, each with fewer host addresses.
For example, if you start with a /24 network (255.255.255.0) and divide it into two subnets, you would use a /25 subnet mask (255.255.255.128), effectively splitting the network into two smaller subnets, each with 128 addresses.
Original Network: 192.168.1.0/24
Subnet 1: 192.168.1.0/25 (Addresses from 192.168.1.0 to 192.168.1.127)
Subnet 2: 192.168.1.128/25 (Addresses from 192.168.1.128 to 192.168.1.255)
4.5 Example of Network Mask in Routing
Here’s an example of how a network mask is used in a routing table:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
10.0.0.0 255.0.0.0 10.1.1.1 5 Ethernet1 BGP
172.16.0.0 255.255.0.0 172.16.1.2 1 Ethernet2 Static
In this example, the subnet mask helps the router identify the size of each destination network and ensures packets are forwarded to the correct next hop.
5. Next Hop
The Next Hop in networking refers to the immediate, next router or gateway to which a data packet should be forwarded on its journey to its destination. The next hop is a critical component of the routing process and is present in each entry of a router’s routing table. It allows routers to incrementally pass packets towards their final destination, even if they are multiple hops away.
5.1 Role of the Next Hop in Routing
When a router receives a packet, it examines its routing table to determine the next hop. The next hop field in the routing table indicates where the router should send the packet next based on the destination IP address. Each router in the path forwards the packet to the next hop until it reaches the destination.
For example, if a router wants to send a packet to a remote IP address (e.g., 203.0.113.1), it does not send it directly to the destination but to the next hop router closer to the destination.
5.2 Types of Next Hop
There are two primary types of next hop scenarios:
- Directly Connected Next Hop: The next hop is directly reachable within the same network or subnet. In this case, the packet is forwarded to a host or router that is part of the same local network.
- Indirect Next Hop: The next hop is a router that is not directly reachable, meaning the packet must pass through intermediate routers to reach the next hop. This is typically the case in larger networks or when routing between different networks.
5.3 Next Hop Resolution
To forward packets correctly, routers must resolve the next hop to a physical address (such as a MAC address). This is achieved through protocols like the Address Resolution Protocol (ARP) in IPv4 networks or Neighbor Discovery Protocol (NDP) in IPv6 networks.
- ARP (Address Resolution Protocol): ARP is used to map an IP address to its corresponding MAC address within the same network.
- NDP (Neighbor Discovery Protocol): NDP is used in IPv6 to discover neighboring devices, including the next hop, and resolve their link-layer addresses.
5.4 Example of Next Hop in a Routing Table
The next hop is displayed in the routing table alongside the destination network, subnet mask, and other routing information. Here's an example:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
10.0.0.0 255.0.0.0 10.1.1.1 5 Ethernet1 BGP
172.16.0.0 255.255.0.0 172.16.1.2 1 Ethernet2 Static
In this routing table:
- The next hop for the 192.168.1.0 network is 192.168.2.1, indicating that packets destined for this network should be sent to the router at IP address 192.168.2.1.
- The next hop for the 10.0.0.0 network is 10.1.1.1, indicating that the next router closer to this destination is 10.1.1.1.
5.5 Importance of Next Hop in Routing Efficiency
The next hop is essential for ensuring the packet takes the most efficient path to its destination. Using the next hop field, routers can make intelligent forwarding decisions, optimizing network performance and minimizing delays.
Additionally, in dynamic routing protocols like OSPF or BGP, the next hop is continuously updated as network conditions change, ensuring that the most optimal path is always selected based on current topology and metrics.
6. Administrative Distance
Administrative Distance (AD) is a value used by routers to rank the trustworthiness of a routing source. It helps routers decide which routing information to prioritize when there are multiple routes to the same destination learned from different routing protocols. The lower the administrative distance, the more trusted the source of the routing information. It ensures that the best possible route is selected based on the trust level assigned to each protocol.
6.1 Role of Administrative Distance in Routing
Routers often learn routes to the same destination from different routing sources or protocols. To resolve these conflicts, the router relies on the AD value of each source. The route with the lowest AD is preferred and added to the routing table. For example, if a router receives a route to a destination from both OSPF and RIP, it will choose the OSPF route because OSPF has a lower AD (110) compared to RIP (120).
6.2 Common Administrative Distance Values
Here are the default administrative distance values for some common routing sources:
- Connected Interface: 0 (The most trusted route as it's directly connected.)
- Static Route: 1
- EBGP (External BGP): 20
- EIGRP (Internal): 90
- OSPF: 110
- RIP: 120
- External EIGRP: 170
- IBGP (Internal BGP): 200
- Unknown/Untrusted: 255 (This route will never be used.)
6.3 Administrative Distance in Action
Consider a scenario where a router receives a route to the network 192.168.1.0/24 from two different routing protocols—OSPF and RIP. The router will compare the AD of both protocols:
- OSPF AD: 110
- RIP AD: 120
Since OSPF has a lower AD (110) compared to RIP (120), the router will prefer the OSPF route and install it in the routing table, while discarding the RIP route.
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF (AD 110)
192.168.1.0 255.255.255.0 192.168.3.1 5 Ethernet1 RIP (AD 120) -> Not used
In this example, even though the RIP route has a better metric (5), the OSPF route is chosen because OSPF has a lower administrative distance, meaning it is more trusted.
6.4 Importance of Administrative Distance
Administrative distance is crucial in environments where multiple routing protocols coexist. It ensures that the most reliable and trustworthy routes are used for forwarding traffic. Without administrative distance, routers might not be able to resolve conflicts between routes from different sources, leading to inefficient routing decisions.
In large, complex networks, network administrators can manually adjust the AD values to fine-tune routing behavior. For example, an administrator might increase the AD of a static route if they want to prioritize dynamically learned routes over static routes in specific scenarios.
7. Metric
The metric in networking is a value used by routing protocols to determine the best path to a destination. It reflects the "cost" of a particular route, and lower metric values indicate more desirable or efficient routes. The specific meaning of the metric varies depending on the routing protocol, but it is a crucial factor in deciding the optimal route for forwarding data packets.
7.1 Role of Metric in Routing
When multiple routes to the same destination exist, routers rely on metrics to choose the most efficient path. The routing protocol calculates the metric based on various factors such as hop count, bandwidth, delay, reliability, and load. The route with the lowest metric is selected and added to the routing table.
7.2 Metrics in Different Routing Protocols
Each routing protocol uses its own method of calculating the metric. Here are examples of how different protocols calculate metrics:
- RIP (Routing Information Protocol): RIP uses the hop count as its metric. Each hop represents a router that the packet must pass through. The route with the fewest hops is preferred. The maximum hop count in RIP is 15, meaning routes with more than 15 hops are considered unreachable.
- OSPF (Open Shortest Path First): OSPF uses cost as its metric, which is calculated based on the bandwidth of the link. The higher the bandwidth, the lower the cost, making faster links more preferable.
- EIGRP (Enhanced Interior Gateway Routing Protocol): EIGRP uses a composite metric based on bandwidth, delay, reliability, and load. EIGRP’s metric calculation is more sophisticated and takes into account multiple factors, leading to more accurate route selection.
- BGP (Border Gateway Protocol): BGP uses various attributes, including the AS Path length as its metric. The shorter the AS Path (fewer autonomous systems the packet traverses), the more preferred the route.
7.3 Example of Metric in a Routing Table
Here is an example of a routing table with metrics:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
10.0.0.0 255.0.0.0 10.1.1.1 5 Ethernet1 RIP
172.16.0.0 255.255.0.0 172.16.1.2 100 Ethernet2 Static
In this routing table:
- The OSPF route to 192.168.1.0 has a metric of 10, which is based on the cost (likely reflecting bandwidth).
- The RIP route to 10.0.0.0 has a metric of 5, representing the hop count.
- The static route to 172.16.0.0 has a manually assigned metric of 100, which is used to rank its preference.
The router will prefer the route with the lowest metric to reach each destination. For example, the route to 10.0.0.0 via 10.1.1.1 is preferred over other routes because it has the lowest metric (5).
7.4 Importance of Metrics in Routing
Metrics are crucial in ensuring that packets are forwarded via the most efficient paths in a network. Without metrics, routers would not be able to distinguish between multiple routes to the same destination, potentially leading to suboptimal performance or network congestion. By dynamically adjusting metrics based on factors like bandwidth, delay, or load, routing protocols can adapt to changes in network conditions and maintain optimal routing behavior.
7.5 Metrics and Dynamic Routing Protocols
In dynamic routing protocols, metrics are continually updated as network conditions change. For instance, if a link becomes congested, the delay may increase, causing the metric for that route to rise. The router will then choose an alternative route with a lower metric, improving overall network efficiency.
In more advanced protocols like EIGRP, metrics consider multiple factors (e.g., bandwidth, delay, reliability), providing a more comprehensive and accurate measure of route efficiency compared to simpler protocols like RIP, which only uses hop count.
8. Gateway of Last Resort
The Gateway of Last Resort refers to the router or gateway that is used to forward packets when no specific route is found in the routing table for the destination network. It is effectively a default route that provides a "fallback" option for handling packets that do not match any more specific routes in the table. The Gateway of Last Resort ensures that packets destined for unknown networks are not dropped and have a chance to be forwarded to their destination through a broader network, often the internet.
8.1 Role of the Gateway of Last Resort
The Gateway of Last Resort acts as a default route, used in scenarios where a packet’s destination does not match any routes in the router's routing table. Without a default route, packets without a matching route would be discarded by the router. The Gateway of Last Resort ensures these packets are forwarded to a specified next-hop device or gateway that has better knowledge or broader connectivity to external networks.
8.2 Default Route as the Gateway of Last Resort
In most cases, the Gateway of Last Resort is set using a default route. A default route is represented as 0.0.0.0/0 in IPv4 or ::/0 in IPv6, meaning it matches all destination IP addresses. This route is used when no other more specific routes exist in the routing table.
0.0.0.0/0 192.168.1.1 1 Ethernet0 Static
::/0 2001:db8::1 1 Ethernet1 Static
In this example, 192.168.1.1 is the default gateway (Gateway of Last Resort) for IPv4, and 2001:db8::1 is the default gateway for IPv6. All packets that do not match any specific routes will be sent to these addresses for further forwarding.
8.3 Importance of the Gateway of Last Resort
The Gateway of Last Resort is essential for connecting local networks to external or unknown networks, such as the internet. Without it, any packet destined for an unknown network would be dropped, limiting the network’s connectivity. By configuring a default route, administrators can ensure that traffic destined for unfamiliar networks is forwarded to a more capable device, like a border router or firewall, which can handle or route the traffic appropriately.
8.4 Configuring the Gateway of Last Resort
The Gateway of Last Resort is typically configured by setting a static default route or allowing a dynamic routing protocol (e.g., OSPF, BGP) to assign the default route. In many cases, network administrators manually set the default route to the device that connects the network to an upstream provider or the internet.
Router(config)# ip route 0.0.0.0 0.0.0.0 192.168.1.1
This command configures the router to forward all packets without a more specific route to the gateway at 192.168.1.1, designating it as the Gateway of Last Resort.
8.5 Example of a Routing Table with a Gateway of Last Resort
Here's an example of a routing table with a Gateway of Last Resort:
Destination Subnet Mask Next Hop Metric Interface Protocol
192.168.1.0 255.255.255.0 192.168.2.1 10 Ethernet0 OSPF
172.16.0.0 255.255.0.0 172.16.1.2 5 Ethernet1 Static
0.0.0.0 0.0.0.0 192.168.1.1 1 Ethernet0 Static (Gateway of Last Resort)
In this example, the default route 0.0.0.0/0 points to 192.168.1.1, which acts as the Gateway of Last Resort. This ensures that any packets not destined for the 192.168.1.0 or 172.16.0.0 networks are forwarded to 192.168.1.1 for further processing.