Network Presentation

STP

There are three types of Spanning Tree Protocol. They are Per VLAN Spanning Tree Protocol, Rapid Spanning Tree Protocol and Multiple Spanning Tree Protocol.

—STP Types
Per VLAN Spanning Tree Protocol is the original STP that detects and prevent loops.

Rapid Spanning Tree Protocol improves on the original protocol by introducing faster convergence times and new port roles, such as alternate and backup ports, which help to reduce the convergence time.

Multiple Spanning Tree Protocol is an enhancement to the original STP. It allows for the creation of multiple spanning trees on a single network, each with its own set of VLANs. This allows for better network optimization and improved performance.

—Election Process
The switch with the lowest bridge ID becomes the root bridge. The root bridge is the reference point for the entire network and is responsible for forwarding traffic through the network.

Once the root bridge has been elected, each switch then selects a root port, which is the port that has the lowest path cost to the root bridge.

Each non-root bridge then selects a designated port, which is the port that has the lowest path cost to the root bridge.

OSPF

OSPF is a is a routing protocol and a link-state protocol, which means that it builds a database of the network topology by exchanging link-state advertisements (LSAs) between routers and to calculate the shortest path to a destination network.

—DR
The router with the highest OSPF priority on the network becomes the DR.

The router with the second-highest OSPF priority becomes the BDR.

—LSA
Each router sends its own LSA Type 1, Route LSA, to all other routers in the same area.

LSA Type 2, Network LSA, is generated by the DR (Designated Router) to non-DR on multi-access networks.

LSA Type 3, Summary LSA, is generated by an Area Border Router (ABR). The LSA contains information about the destination network, the cost to reach the network.

LSA Type 4, ASBR Summary LSA, is generated by an ABR and describes the state of an Autonomous System Boundary Router (ASBR).

LSA Type 5, External LSA, is generated by an ASBR and describes the state of external networks.

EIGRP

EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary protocol and an advanced distance-vector routing protocol.

It supports features such as fast convergence, load balancing, and route summarization.

It uses a metric called the composite metric, which takes into account factors such as bandwidth, delay, reliability, and load to calculate the best path to a destination network.

If the successor route fails, the DUAL algorithm then searches for a feasible successor route. To qualify as a feasible successor route, the advertised distance of the path must be less than the feasible distance of the current successor path.

IPsec

IPsec (Internet Protocol Security) is a set of protocols used to provide secure communication over IP-based networks such as the Internet. It provides a framework for encrypting and authenticating IP packets, which helps to protect the confidentiality, integrity, and authenticity of network communications.

Phase 1, also known as the IKE (Internet Key Exchange) phase, is used to establish a secure and authenticated communication channel between the two hosts. During this phase, the hosts negotiate which encryption and authentication algorithms to use, as well as a shared secret key that will be used to encrypt and authenticate the data traffic in Phase 2. The IKE protocol uses a Diffie-Hellman key exchange to securely establish the shared secret key.

Phase 2, also known as the IPsec tunnel phase, is used to establish a secure tunnel for data traffic between the two hosts. During this phase, the hosts negotiate the specific parameters of the IPsec tunnel, including the encryption and authentication algorithms, the mode of operation (transport or tunnel), and the traffic selectors (which define which traffic will be protected by the IPsec tunnel). Once the parameters are agreed upon, the hosts can begin to securely exchange data traffic over the IPsec tunnel.

In summary, Phase 1 of IPsec is used to establish a secure and authenticated communication channel between two hosts, while Phase 2 is used to establish a secure tunnel for data traffic between the hosts.

BGP

BGP (Border Gateway Protocol) is a routing protocol used to exchange routing information between different autonomous systems (AS) on the Internet. An autonomous system is a collection of networks under a common administrative domain, such as an Internet Service Provider (ISP) or a large enterprise network.

BGP is a path vector protocol, which means that it selects the best path for a packet based on a set of attributes associated with each route. These attributes can include the length of the AS path, the origin of the route, the next hop, and other factors.

0.

1. Weight is a Cisco-specific attribute that is used to influence the best path selection within a single router. A higher weight value indicates a better path.
2. Local preference is an attribute used to influence the best path selection within a single autonomous system (AS). A higher local preference value indicates a better path.
3. Locally originated routes from the ‘network’
4. AS path length is the number of autonomous systems that a route has traversed to reach the destination network. A shorter AS path length indicates a better path.
5. Origin type indicates how a particular route was originated. A route that is originated from within the local AS is preferred over a route that is learned from an external AS.
6. MED is an attribute used to influence the best path selection between multiple paths learned from the same autonomous system. A lower MED value indicates a better path.
7. eBGP path preference is used to determine the best path when multiple paths are learned from different autonomous systems. A path learned via external BGP (eBGP) is preferred over a path learned via internal BGP (iBGP).
8. IGP (Interior Gateway Protocol) metric is used to influence the best path selection when multiple paths are learned via the same AS. A lower IGP metric value indicates a better path.
9. Lowest router ID

In summary, the BGP attribute priority determines the order in which the BGP attributes are evaluated to select the best path for a packet. The attributes with higher priority are evaluated first, and the attributes with lower priority are evaluated only if the higher priority attributes are equal.