Routing Protocol and Concepts

Routing Protocol and Concepts
หลักสูตรผู้เชี่ยวชาญระบบโครงข่ายการศึกษาขั้นพื้นฐาน (OBEC Network)

ลักษณะการส่ง Packet ใน IP Network จะส่งทีละ Hop จาก Network หนึ่ง ไปยังอีก Network หนึ่ง Router จะทำหน้าที่ดังกล่าว เนื่องจาก Router เป็นตัวเชื่อมระหว่าง Network การส่งจะดูที่ส่วน Prefix ของ IP Address ดังนั้น Router จะต้อง Run IP Protocol คือทำงานในระดับ Layer 3 ที่ Router จะมีตารางชื่อ Routing Table ที่กำหนด IP Address ของ Next Hop

Static Routing : หมายถึงตาราง Routing Table ของ Router แต่ละตัวจะไม่เปลี่ยน ปกติตารางนี้จะถูกกำหนดจาก Network Administrationคือตารางนี้จะได้จากการทำ Configuration ของ Router Dynamic Routing : หมายถึงตาราง Routing Table สามารถเปลี่ยนได้ ตามสภาวะความคับคั่งของ Network ขณะนั้นหรือจากปัจจัยอื่นๆ โดยมันจะมีการ Update ตลอดเวลา

หน้าที่หลักของ router การพิจารณาคัดเลือกเส้นทางในการส่งผ่านข้อมูลไปยังเครือข่ายคอมพิวเตอร์อื่น ๆ (Internetworking Device) การส่งผ่านข้อมูลของ Router จะใช้โปรโตคอล IP โดยทำงานอยู่บนระดับชั้นที่ 3 ของแบบจำลอง OSI Model Routers generally have 2 connections: -WAN connection (Connection to ISP) -LAN connection

Data is sent in form of packets between 2 end devices Routers are used to direct packet to its destination

Routers examine a packet’s destination IP address and determine the best path by enlisting the aid of a routing table

ส่วนประกอบของ router และ ฟังก์ชั่นการทำงาน CPU Random access memory (RAM) Read-only memory (ROM) Non-volatile RAM (NVRAM) Flash memory Interfaces -Ethernet / fast Ethernet interfaces -Serial interfaces -Management interfaces CPU - Executes operating system instructions Random access memory (RAM) - Contains the running copy of configuration file. Stores routing table. RAM contents lost when power is off Read-only memory (ROM) - Holds diagnostic software used when router is powered up. Stores the router’s bootstrap program. Non-volatile RAM (NVRAM) - Stores startup configuration. This may include IP addresses (Routing protocol, Hostname of router) Flash memory - Contains the operating system (Cisco IOS) Interfaces - There exist multiple physical interfaces that are used to connect network. Examples of interface types: -Ethernet / fast Ethernet interfaces -Serial interfaces -Management interfaces

Router components

กระบวนการทำงานของ router Test router hardware Power-On Self Test (POST) Execute bootstrap loader Locate & load Cisco IOS software -Locate IOS -Load IOS Locate & load startup configuration file or enter setup mode -Bootstrap program looks for configuration file

การตรวจสอบข้อมูลของตัว router -The show version command is used to view information about the router during the bootup process. Information includes: Platform model number Image name & IOS version Bootstrap version stored in ROM Image file name & where it was loaded from Number & type of interfaces Amount of NVRAM Amount of flash Configuration register

Router Interface is a physical connector that enables a router to send or receive packets Each interface connects to a separate network Consist of socket or jack found on the outside of a router Types of router interfaces: -Ethernet -Fastethernet -Serial -DSL -ISDN -Cable

Two major groups of Router Interfaces LAN Interfaces: Are used to connect router to LAN network Has a layer 2 MAC address Can be assigned a Layer 3 IP address Usually consist of an RJ-45 jack WAN Interfaces Are used to connect routers to external networks that interconnect LANs. Depending on the WAN technology, a layer 2 address may be used. Uses a layer 3 IP address

Routers and the Network Layer Routers use destination IP address to forward packets The path a packet takes is determined after a router consults information in the routing table. After router determines the best path Packet is encapsulated into a frame Frame is then placed on network medium in form of Bits

Routers Operate at Layers 1, 2 & 3 Router receives a stream of encoded bits Bits are decoded and passed to layer 2 Router de-encapsulates the frame Remaining packet passed up to layer 3 -Routing decision made at this layer by examining destination IP address Packet is then re-encapsulated & sent out outbound interface

หลักสูตรผู้เชี่ยวชาญระบบโครงข่ายการศึกษาขั้นพื้นฐาน (OBEC Network)
Static Routing หลักสูตรผู้เชี่ยวชาญระบบโครงข่ายการศึกษาขั้นพื้นฐาน (OBEC Network)

General Role of the Router
Functions of a Router Best Path Selections Forwarding packets to destination Introducing the Topology series routers connected via WAN links Each router connected to a LAN represented by a switch and a PC

General Role of the Router
Connections of a Router for WAN -A router has a DB-60 port that can support 5 different cabling standards Connections of a Router for Ethernet -2 types of connectors can be used: Straight through and Cross-over Straight through used to connect: -Switch-to-Router, Switch-to-PC, Router-to-Server, Hub-to-PC, Hub-to-Server Cross-over used to connect: -Switch-to-Switch, PC-to-PC, Switch-to-Hub, Hub-to-Hub, Router-to-Router Use Graphic

Interfaces Examining Router Interfaces
-Show IP router command – used to view routing table -Show Interfaces command – used to show status of an interface -Show IP Interface brief command – used to show a portion of the interface information -Show running-config command – used to show configuration file in RAM

Interfaces Configuring an Ethernet interface
-By default all serial and Ethernet interfaces are down -To enable an interface use the No Shutdown command

Interfaces Verifying Ethernet interface
-Show interfaces for fastEthernet 0/0 – command used to show status of fast Ethernet port -Show ip interface brief -Show running-config Ethernet interfaces participate in ARP

Interfaces Configuring a Serial interface
-Enter interface configuration mode -Enter in the ip address and subnet mask -Enter in the no shutdown command Example: -R1(config)#interface serial 0/0 -R1(config-if)#ip address -R1(config-if)#no shutdown

Interfaces Examining Router Interfaces
-Physically connecting a WAN Interface. -A WAN Physical Layer connection has sides: Data Circuit-terminating Equipment (DCE) – This is the service provider. CSU/DSU is a DCE device. Data Terminal Equipment (DTE) – Typically the router is the DTE device. Use graphic ….would suggest modifying graphic such that each component is identified prior to placing on slide

Interfaces Configuring serial links in a lab environment
One side of a serial connection must be considered a DCE This requires placing a clocking signal – use the clock rate command. Example: -R1(config)#interface serial 0/0 -R1(config-if)#clockrate 64000 Serial Interfaces require a clock signal to control the timing of the communcations. Use graphic topology. If you can fit the router output that would be great but if not just use the topology

Routing Table and CDP Protocol
Purpose of the debug ip routing command Allows you to view changes that the router performs when adding or removing routes Example: -R2#debug ip routing -IP routing debugging is on Use graphic ….in particular the “debug 1”

To configure an Ethernet interface Example: -R2(config)#interface fastethernet 0/0 -R2(config-if)#ip address -R2(config-if)#no shutdown

When a router only has its interfaces configured & no other routing protocols are configured then: -The routing table contains only the directly connected networks -Only devices on the directly connected networks are reachable

Checking each route in turn The ping command is used to check end to end connectivity

Purpose of CDP A layer 2 cisco proprietary tool used to gather information about other directly connected Cisco devices. Concept of neighbors -2 types of neighbors Layer 3 neighbors Layer 2 neighbors Use graphic associated with CDP protocols (graphic )

CDP show commands Show cdp neighbors command -Displays the following information: Neighbor device ID Local interface Holdtime value, in seconds Neighbor device capability code Neighbor hardware platform Neighbor remote port ID Show cdp neighbors detail command -Useful in determining if an IP address configuration error

Disabling CDP To disable CDP globally use the following command Router(config)#no cdp run Use router output graphic (all 3) – this will cover this slide and the previous slide

Static Routes with Exit Interfaces
Purpose of a static route A manually configured route used when routing from a network to a stub network

IP route command To configure a static route use the following command: ip route Example: -Router(config)# ip route network-address subnet-mask {ip-address | exit-interface }

Dissecting static route syntax ip route - Static route command – Destination network address Subnet mask of destination network Serial 0/0/0 interface IP address on R2, which is the "next-hop" to this network

Configuring routes to 2 or more remote networks Use the following commands for R1 -R1(config)#ip route -R1(config)#ip route

Zinin’s 3 routing principles Principle 1: "Every router makes its decision alone, based on the information it has in its own routing table.“ Principle 2: "The fact that one router has certain information in its routing table does not mean that other routers have the same information.“ Principle 3: "Routing information about a path from one network to another does not provide routing information about the reverse, or return path."

Using Zinin’s 3 routing principles, how would you answer the following? -Would packets from PC1 reach their destination? Yes, packets destined for /24 and /24 networks would reach their destination. -Does this mean that any packets from these networks destined for /24 network will reach their destination? No, because neither R2 nor R3 router has a route to the /24 network.

Modifying Static routes Existing static routes cannot be modified. The old static route must be deleted by placing no in front of the ip route Example: -no ip route A new static route must be rewritten in the configuration

Verifying the Static Route Configuration -Use the following commands Step 1 show running-config Step 2 verify static route has been entered correctly Step 3 show ip route Step 4 verify route was configured in routing table Step 5 issue ping command to verify packets can reach destination and that Return path is working

Ethernet interfaces and ARP. If a static route is configured on an Ethernet link -If the packet is sent to the next-hop router then… the destination MAC address will be the address of the next hop’s Ethernet interface This is found by the router consulting the ARP table. If an entry isn’t found then an ARP request will be sent out

Summary and Default Route
Summarizing routes reduces the size of the routing table. Route summarization is the process of combining a number of static routes into a single static route. Use graphic

Configuring a summary route Step 1: Delete the current static route Step 2: Configure the summary static route Step 3: Verify the new static route

Default Static Route This is a route that will match all packets. Stub routers that have a number of static routes all exiting the same interface are good candidates for a default route. -Like route summarization this will help reduce the size of the routing table Configuring a default static route Similar to configuring a static route. Except that destination IP address and subnet mask are all zeros Example: -Router(config)#ip route [exit-interface | ip-address ]

Static routes and subnet masks The routing table lookup process will use the most specific match when comparing destination IP address and subnet mask Default static routes and subnet masks Since the subnet mask used on a default static route is all packets will match. Use graphic

การใช้ Static Route ควรมีการกำหนด Default Route เสมอ
Summary ข้อดีของ Static Routing คือง่าย และไม่ต้องใช้ Routing Software(Router จะทำงานน้อยลง) นอกจากนี้จะไม่ใช้ Resource ของ Network เพราะ Router ไม่ต้องแลกเปลี่ยนข้อมูลกัน ข้อเสียคือ ตารางเปลี่ยนไม่ได้ ถ้ามี Link Down หรือ Router Down เส้นทางนั้นจะใช้ไม่ได้ ทำให้การส่งข้อมูลที่กำหนดเส้นทางนั้นหยุดชะงักหรือใช้กำหนดสำหรับ Host ที่เชื่อมต่อกับ Network ที่มีทางออกผ่าน Router ตัวเดียว(คือค่า Gateway) การใช้ Static Route ควรมีการกำหนด Default Route เสมอ การทำ Static Route ต้องตรวจสอบให้ดีว่าจะไม่มี Route Loop Use graphic

Basic Static Route (LAB 2.8.1)

Dynamic Routing Protocol

Dynamic Routing Protocols
Function(s) of Dynamic Routing Protocols: -Dynamically share information between routers. -Automatically update routing table when topology changes. -Determine best path to a destination.

The purpose of a dynamic routing protocol is to: -Discover remote networks -Maintaining up-to-date routing information -Choosing the best path to destination networks -Ability to find a new best path if the current path is no longer available

Components of a routing protocol Algorithm In the case of a routing protocol algorithms are used for facilitating routing information and best path determination Routing protocol messages These are messages for discovering neighbors and exchange of routing information

Advantages of static routing -It can backup multiple interfaces/networks on a router -Easy to configure -No extra resources are needed -More secure Disadvantages of static routing -Network changes require manual reconfiguration -Does not scale well in large topologies

Classifying Routing Protocols
Dynamic routing protocols are grouped according to characteristics. Examples include: -RIP -IGRP -EIGRP -OSPF -IS-IS -BGP Autonomous System is a group of routers under the control of a single authority.

Types of routing protocols: -Interior Gateway Protocols (IGP) -Exterior Gateway Protocols (EGP)

Interior Gateway Routing Protocols (IGP) -Used for routing inside an autonomous system & used to route within the individual networks themselves. -Examples: RIP, EIGRP, OSPF Exterior Routing Protocols (EGP) -Used for routing between autonomous systems -Example: BGPv4

IGP: Comparison of Distance Vector & Link State Routing Protocols Distance vector routes are advertised as vectors of distance & direction. incomplete view of network topology. Generally, periodic updates. Link state complete view of network topology is created. updates are not periodic.

Distance-vector algorithms (Bellman-Ford algorithms) แต่ละ router ส่งข้อมูลทั้งหมดหรือบางส่วนของ routing table ของตัวเองแต่ส่งให้เฉพาะ router ที่อยู่ติดกัน จุดสำคัญ link-state algorithms ส่ง small update ไปทุก ๆ ที่ขณะที่ distance-vector algorithms ส่ง large update ไปเฉพาะ router ที่อยู่ติดกัน Distance-vector algorithms จะทราบข้อมูลเกี่ยวกับ router ที่อยู่ติดกันเท่านั้น

Link-state algorithms (shortest path first algorithms) จะส่ง routing information ถึงทุก node ใน internetwork แต่ละ router ส่งบางส่วนของ routing table ที่อธิบายสถานะของการเชื่อมโยงของตัวเอง ใน link-state algorithms แต่ละ router สร้างภาพของเครือข่ายทั้งหมดใน routing tables

Classful routing protocols Do NOT send subnet mask in routing updates Classless routing protocols Do send subnet mask in routing updates.

Convergence is defined as when all routers’ routing tables are at a state of consistency

Routing Protocols Metrics
A value used by a routing protocol to determine which routes are better than others.

Metrics used in IP routing protocols -Bandwidth -Cost -Delay -Hop count -Load -Reliability

The Metric Field in the Routing Table Metric used for each routing protocol -RIP - hop count -IGRP & EIGRP - Bandwidth (used by default), Delay (used by default), Load, Reliability -IS-IS & OSPF – Cost, Bandwidth (Cisco’s implementation)

Load balancing This is the ability of a router to distribute packets among multiple same cost paths

Administrative Distance of a Route
Purpose of a metric It’s a calculated value used to determine the best path to a destination Purpose of Administrative Distance It’s a numeric value that specifies the preference of a particular route

Identifying the Administrative Distance (AD) in a routing table It is the first number in the brackets in the routing table

Dynamic Routing Protocols

Directly connected routes Have a default AD of 0 Static Routes Administrative distance of a static route has a default value of 1

Directly connected routes -Immediately appear in the routing table as soon as the interface is configured

Summary Dynamic routing protocols fulfill the following functions
-Dynamically share information between routers -Automatically update routing table when topology changes -Determine best path to a destination Routing protocols are grouped as either -Interior gateway protocols (IGP)Or -Exterior gateway protocols(EGP) Types of IGPs include -Classless routing protocols - these protocols include subnet mask in routing updates -Classful routing protocols - these protocols do not include subnet mask in routing update

Summary Metrics are used by dynamic routing protocols to calculate the best path to a destination. Administrative distance is an integer value that is used to indicate a router’s “trustworthiness” Components of a routing table include: -Route source -Administrative distance -Metric

Basic RIP Configuration (Lab 7.5.1)

Basic EIGRP Configuration (Lab 9.6.1)

http://www.youtube.com/watch?v=IQaHd6tos7k summary day1

Routing Protocol and Concepts

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Routing Protocol and Concepts

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