CompTIA Network+ N10-008 Study Guide

Chapter 10 Routing Protocols

Objectives

2.1. Compare and contrast various devises, their features, and their appropriate placement on the Network 2.2 ompare and ocntrast routing technologies and bandwidth management concepts 2.3 Give a scenario, configure and deploy common Ethernet switch features

Routing Protocol Basics

  • AS (Autonomous Systems) Which are systems that are on an internet gateway protocol (IGP), or external gateway protocol (EGP) and share IP (Internet Protocol) table information.
  • IGP (Internal Gateway Protocol) has to do with how routers share information on an intranet
  • EGP (Exterior Gateway Protocol) has to do with how routers share information on the Internet
  • BGP (Border Gateway Protocol) is an implementation of an EGP (Exterior Gateway Protocol)
  • EIGRP (Enhanced Interior Gateway Routing Protocol) Cisco proprietary routing protocol
  • OSPF (Open Shortest Path First)
  • IS-IS (Intermediate System to Intermediate System)

Administrative Distance (Choosing the best routes)

AD (Administrative Distance) is a caluclation that stores numbers 0 to 255 where 0 is the best route, and 255 is the worst route. 255 is a metric meaning that a packet should not be forwarded through that router.

A router may receive one or more updates. If there are two updates at the same time the router will look at the route with the lowest Administrative Distance. If they both have the same Administrative Distance (AD) then the one with the fewest TTL (time to live) or hopshops on the network is chosen. If two routes have the same metrics then a bandwidth metric is continuously calculated and the router will load balance.

Default Routing Sources

Route Source Default AD (Administrative Distance)
Connected Interface 0
Static Route 1
External BGP (Border Gateway Protocol) 20
Internal EIGRP (Ehanced Internal Gateway Routing Protocol) 90
IGRP (Internal Gateway Routing Protocol 100
OSPF (Open Shortest Path First) 110
IS-IS (Internal system to Internal System) 115
RIP (Routing Information Protocol) 120
External EIGRP (Enhanced Internal Gateway Routing Protocol) 170
Internal BGP (Border Gateway Protocol) 200
Unknown 255

Classes of Routing Protocols

  • Distance Vector - Calculates the distances between one node and another node with hops and determine best path
  • Link State - Shortest Path Protocols keep maps that are updated from their neighbors about best paths to take and their routes
  • Hybrid - EIGRP (Enhanced Internal Gateway Route Protocol) and BGP (Border Gateway Protocol) are examples of the hybrid state where they use both distance vector protocols and they use link state protocols to determine best path

Distance Vector Routing Protocol

Uses a strategy called routing by rumor which receives and sends routing table updates which are then used to determine best path for packets

Distance vectors will do something called convergence which helps them finally reach an agreement on the information for the ermote network number, the interface that the router will use to send packets to reach that particular network, the hop count, or metric, to the network

Routing Information Protocol (RIP)

  • Works as as Distance Vector calculation
  • Is slow for convergence time
  • Transmitted every 30 seconds to update nearby routers with it’s routing table information
  • Uses hop count to determine best path
  • Good with smaller networks but not for enterprise networks or WAN
  • Only uses cassful routing which means all devices on the network must share the same subnet
  • Broadcast based
  • Supports no Authentication mechanisms

RIP (Routing Information protocol) V2 (RIPv2)

  • Works as a Distance Vector protocol
  • Supports Variable Length Subnet Masks (VLSMs)
  • Can use a classful protocol unlike RIPv1
  • use multicast 224.0.0.9
  • Supports MD5 Authentication

VLSMs and Discontiguous networks

  • has two or more subnetworks of a classful network connected together by different classful network
  • Does not work with any other protocol other than OSPF (Open Shortest Path First). EIGRP, RIPv1, and RIPv2 all do not work with this strategy

EIGRP (Enhanced Internal Gateway Routing Protocl)

  • Proprietary to Cicsco
  • Classless
  • Distance Vector
  • Uses the Autonomous System to share routing information
  • Differs from IGRP in that it also shares the subnet mask information
  • Subpports VLSM (Variable Lenth Subnet Masks)
  • Comunication is completed using Reliable Transport Protocol (RTP)

BGP (Border Gateway Protocol)

  • External Routing Protocol
  • Used between Autonomous Systems
  • Heavily utilizedby ISPs (Interent Service Providers)
  • Uses Classless routing
  • Used by IGPs (Internal Gateway Protocols) to connect AS (Autonomous Systems) in larger networks
  • Technically is a EGP (External Gateway Protocol)
  • Uses something Call the RIB (Routing Information Base) and doesn’t broadcast its entire routing table the same way RIP does
  • OSPF (Open Shortest Path First) and IS-IS, (Internal System to Internal System) are examples
  • Classless Routing
  • Can learn and maintain much mor einformation than the distance vector protocols
  • Maintains a neighbor table which helps identity what the cost is for sending packets to a neighbor
  • Maintains a Topology Table which helps direct the flow of traffic
  • Uses SPF (Shortest Path First) protocol to decide where to direct traffic using the topology, neighbor, and its own AD (Administrative Direction) Table

Open Shortest Path First (OSPF)

  • Open Standard Protocol
  • Utilizes Dijkstras Algorithm
  • Has fast convergence
  • Supports IP and IPv6
  • Minimizes routing update trafficAllows scalabilit Supports VLSM/CIDR
  • Has unlimited hop count
  • Allows multivendor deployment
  • Uses a loopback interface to keep the network stable

High Availability

  • First-hop redundancy protocols (FHRPs) work by giving you a way to configure more than on physical router to appears asif they were only a single logical one
  • Uses a Virtual Router which has its own IP (Internet Protocol) and MAC (Media Access Control) Address that each client communiates with. The IP (Internet Protocol) Address is the Default Gateway the client uses and the MAC (Media Access Control) Address is the ARP (Address Resolution Protocol) response used by the client
  • Acts as a medium between routers which may go down and need to forward traffic to a different router or network

Hot Standby Router Protocol (HSRP)

  • Cisco Proprietary protocol that provides redundant gateway for hosts on a local subnit. Routers are allowed to share MAC Addresses and IP Addresses in the protocol such that it becomes transparent to the clients whom they are communicating with in the event that a router goes down
  • Virtual Router Redundancy Protocl (BRRP) Open Source protocol version of the HSRP
  • Maintains several backup routers which remain idle until failure occurs with the main router
  • Uses timers which are called hello, hold, active, and standby
  • Hello Timer Runs in a default interval of 3 seconds and identifies th state of which the router is in. Routers today are commonly configured in milliseconds.
  • Hold Timer Hold timer is a way for a standby router to identify whether the active router is offline or not. The default time is 10 seconds. An Algorithm of 3x the hello timer is used as a way of setting this timer.
  • Active Timer Active timer is used with the hold timer as a way of determining if the standby router should be the active router. Everytime the standby router receives a hello timer request the active timer is reset
  • Standby Timer used to monitor thes tate of the standby router. Resets anytme a router in the standby group receives a hello packet from the standby router and expires based on the hold time value that’s set in the respective Hello packet.
Virtual MAC (Media Access Control) Address
  • Used by HSRP (Hot Standby Router Protocol)
  • Is proprietary to Cisco
  • Uses 0000.0c07.ac0a as a well known address for this protocol

VRRP (Virtual Router Redundancy Protocol)

  • IEEE Standard (RFC 2338)
  • VRRP is something that represetns a group of virtual routers
  • Master router is he active virtual router
  • Master router may have the same IP address as the virtual router group
  • Multiple routers may act as backups
  • Provides redundancy for he real IP of a router or virtual appliances
  • Master router is the one with the real IP (Internet Protocol) address in use
  • Master routers with are assigned by highest priority when virtual IP (Internet Protocol) addresses are in use
  • Master router uses VRRP messages to update other routers of its status
  • Allows load sharing across many other routers

Advanced IPv6 Concepts

Router Advertisement

Process used in IPv6 for hosts to find a NetworkID and generate their own IPv6 Address on the network

Three Step Process for Hosts to receive an address

Process is stateless autoconfiguration because the host is generating its own IPv6 address using MAC (Media Access Control) Address and the Network ID

  1. Host sends s Router solicitation (RS) request for route prefix (Network ID) as a multicast message (FF02::2) as an ICMP message with type 133
  2. Router responds with RA (Router Advertisement) message as a multicast message (FF02::1) and is ICMP type 134
  3. Host generates an address after receiving a message

Neighbor Discover Protocol (NDP)

  • Does not use ARP (Address Resolution Protocol). These systems use Link-Local Addresses instead of MAC (Media Access Control) Addresses
  • Operates at the Data Link Layer (Layer 2)
  • Link Local Addresses always have the prefix FE80::/64
  • Link Local Addresses are discoverd using neighbor discovery with neighbor solicitation and neighbor advertisement messages

Tunneling

  • Used as a way of encapsulating one potocol with another protocol to support IPv6
  • GRE (Generic Routing Encapsulation) is one process that is not commonly used in IPv6 but is commonly used with VPN (Virtual Private Networks) over an IPSec tunnel using encryption
  • 6to4 Tunneling Encapsulates IPv6 Addresses with an IPv4 address by appending a header and using the IPv4 protocol type 41
  • Manual Tunnels are configured by telling routers or smart switches where the tunnel starts and where it ends on a network, and giving it the mode (ipv6ip)
  • 6to4 (automatic) Used by appending the prefix 2002 to the Ipv4 address assigned to the site. No tunnel destination address is set because the destination is automatically constructed.
  • ISATAP Tunneling IPv6 packets over an IPv4 network. Servers are automatically set up to work, but clients must be configured to connect
  • Teredo gives full IPv6 connectivity for IPv6 hosts that are on an Ipv4 network but have no direct native connection to an IPv6 network
  • Dual Stack most common migration strategy that allows for one-to-one replace

IPv6 Routing Protocols

RIPng

  • Similar as RIPv2 in capabilities
  • Distance Vector calculation
  • Uses Multicast to send its updates too but in Ipv6 it uses FF02::9
  • Improvment on RIPv2 is that it keeps the number of hops to the next addressing using the link-local address, not aglobal address.

EIGRPv6 (Enhanced Internal Gatway Routing Protocol v6)

  • Advanced Distance Vector Protocol
  • Hello Packets and updates are sent using multicast transmission and as with RIPing