Transcript Meyers_CompTIA_4e_PPT_Ch08x

Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Routing
Chapter 8
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Objectives
• Explain how routers work
• Describe dynamic routing technologies
• Install and configure a router successfully
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Historical/Conceptual
How Routers Work
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
How Routers Work
• Hardware that forwards packets based on
destination IP address
• Works at the Network layer of the OSI model
– Internet layer of the TCP/IP model
• Typically dedicated boxes with at least two
connections
• Popular router: Cisco 2600 Series
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.1 Cisco 2611 router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
How Routers Work (cont’d.)
• Home router
– First exposure to a router for most techs
– May combine router, switch, firewall, and DHCP
server
• Functions of all routers
– Connect two networks (or subnets/LANs)
– Examine packets and send to proper destination
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.2 Business end of a typical home router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.3 Cisco router diagram
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.4 Linksys home router diagram
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Test Specific
Routing Tables
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Routing Tables
• Packets come into the router for handling
• The router strips off Layer 2 information
– Drops IP packet into a queue based on arrival time
• The router inspects the destination IP address
• The router sends the IP packet out the correct
port
• The routing table tells the router where to
send packets
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.5 Incoming packets
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.6 All incoming packets stripped of Layer 2
data and dropped into a common queue
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
What’s Up with Layer 2?
• Example: home router (See Figure 8.7)
– Two ports
• One connects to ISP
• One connects to built-in four-port switch
– Each row in table defines a single route
– Each column identifies specific criteria
• Destination LAN IP
• Subnet mask
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.7 Routing table from a home router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
What’s Up with Layer 2? (cont’d.)
• The router examines the destination LAN IP
and subnet mask to see if the packet matches
that route
• Gateway
– Identifies the IP address for the next hop router
• Interface
– Identifies which router port to use (LAN or WAN)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.8 Routing table showing the route for a packet
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Router and the Routing Table
• The router reads every line in the router table
and then decides what to do
– May read top down or bottom up
– A zero (0) means “anything”
• Default route for the router in the example
– Shown on third line of the routing table
• Every node on the network has a routing table
– Computer, printer, etc.
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.9 The network based on the routing table in Figure 8.7
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Routing Table Information
• Windows routing table (next slide)
– Computer IP address: 10.12.14.201/24
– Computer loopback: 127.0.0.1
• Metric
– Relative value defining the “cost” of using a route
– If more than one route exists, route with lower
metric value is used
– If route fails, alternate route used
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.10 Two routes to the same network
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.11 When a route no longer works, the router
automatically switches
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Computer Routing Table
• Line 1 (beginning 0.0.0.0) defines the default
route
– (Any destination address) (with any subnet mask)
(forward it to my default gateway) (using my NIC)
(metric of 25 to use this route)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Computer Routing Table
• Lines 2, 3, and 4 tell the system how to handle
the loopback address
– No matter how you use a loopback address, as
long as you start the address with 127, it will
always go to 127.0.0.1
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Computer Routing Table (cont’d.)
• Line 5 (beginning with 10.12.14.0) defines the
local connection
– (Any packet for the 10.12.14.0) (/24 network ID)
(don’t use a gateway) (just ARP on the LAN
interface to get the MAC address and send it
directly to the recipient) (cost of 1 to use this
route)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Computer Routing Table (cont’d.)
• Line 6 (beginning with 10.12.14.201)
– Anything addressed to this machine should go
right back to it through the loopback (127.0.0.1)
• Line 7 is the directed broadcast
• Lines 8 and 9 are for the multicast address
range
• Bottom lines define the default IP broadcast
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Freedom From Layer 2
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Functions of Routers
• Connect different network technologies
• Strip off all Layer 2 data
• Connect to almost anything that stores IP
packets
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Non-Ethernet Network Technologies
• Examples
– Data Over Cable Service Interface Specification
(DOCSIS)
– Frame Relay
– Asynchronous Transfer Mode (ATM)
• All carry IP packets inside their Layer 2
encapsulations
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Added Ports
• Most commercial-grade routers allow adding
ports
– Cisco routers come with removable modules
– Connecting Ethernet to ATM
• Buy an Ethernet and an ATM module
– Connecting Ethernet to DOCSIS
• Buy an Ethernet and a DOCSIS module
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.12 Modular Cisco router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Address Translation
(NAT)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Address Translation
• TCP/IP problems
– Malicious programmers target IP addresses
– IPv4 addresses are not readily available
• NAT enables routers to hide IP addresses of
computers on a LAN from outside networks
– Enables communication with outside networks
• NAT extended the useful life of IPv4
addressing
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Setup
• Acquire a block of unique IP addresses from
an ISP
• Assign an IP address to each computer and to
the LAN connection on the router
• Assign IP address of the ISP’s router to the
WAN connection on the local router
• Give all LAN hosts the IP address of the
gateway router: can act as a default gateway
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.13 Network setup
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Basic NAT and Port Address Translation
(PAT)
• Basic NAT
– Translates internal IP address to global IP address
on a one-to-one basis
• PAT
– Uses port numbers to map traffic from specific
machines in the network
– Example: Figure 8.14
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.14 John’s network setup
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.15 PAT in action -- changing the source IP address and
port number to something usable on the Internet
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
NAT Translation Table
• Used by the router to determine which IP
address to put back on the packet
– Sends the packet to the correct computer on the
network
• Mapping enables perfect tracking of packets
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
SNAT and Port Forwarding
• Static NAT (SNAT)
– Maps a single routable IP address to a single
machine
• Port forwarding
– Designates a specific local address for various
network services
– Hides a service hosted inside your network by
changing the default port number for that service
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.16 Setting up port forwarding on a home router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.17 Changing the URL to access a Web site
using a nondefault port number
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Configuring NAT
• Home routers often have NAT turned on by
default
– The router is set to Gateway
• To turn off NAT, set the radio button to Router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.18 NAT setup on home router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.19 Configuring NAT on a commercial-grade router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Dynamic Routing
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Background
• Routers have static routes
– Manually entered
– Detected at setup by the router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Dynamic Routing Protocols
• Routers communicate among themselves with
change information
– Update each other on changes about direct
connections and distant routers
• A passage of a packet through a single router
is a hop
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.20 Lots of routers
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.21 Hopping through a WAN
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Routing Metrics
• Routing tables contain metrics—a relative
value that routers use when there is more
than one route to another network
– Metrics determine which route to use
– Route with lowest-value metric is selected
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Common Criteria for Determining a
Metric
• Hop count
– The number of routers a packet will pass through
on the way to its destination network
• Bandwidth: connection speed
• Latency
– Issues that may slow network traffic over given
links
• Cost
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Distance Vector
• First of the TCP/IP routing protocols
• The protocol’s cornerstone is total cost
• Simple total cost adds up the hop count
between a router and a destination network
• Example: four routers connected as shown in
Figure 8.22
– Static routes are set up with metrics shown
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.22 Getting a packet from Network ID X to
Network ID Y? No clue!
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.23 Routes updated
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.24 Updated routing tables
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.25 Deleting higher-cost routes
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.26 Argh! Multiple routes!
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.27 Last iteration
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Convergence
• Point at which the updating of all routing
tables is complete
– Also called steady state
• Routers that use distance vector routing
protocols continue to send each other entire
routing tables
• If a route breaks, the router cannot send to
that destination until router table is updated
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Routing Information Protocol (RIPv1)
• Oldest distance vector routing protocol
– Dates from the 1980s; predecessors date to
the 1960s
• Maximum hop count of 15
• Routing table request could loop all the way
back to the initial router
• Sent out an update every 30 seconds
– Caused huge network overloads
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
RIPv1 (cont’d.)
• Did not work with Variable-Length Subnet
Masking (VLSM)
• No authentication ► left routers open to
hackers sending false routing table
information
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
RIPv2
• Current version of RIP
– Adopted in 1994
• Fixed many problems with RIPv1
– VLSM support added
– Authentication built into the protocol
– Most routers still support RIPv2
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.28 Setting RIP in a home router
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
BGP
• Growth of the Internet in the 1980s led to
changes initiated through Internet governing
entities
– Internet Society (ISOC)
– Internet Assigned Numbers Authority (IANA)
– Internet Engineering Task Force (IETF)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
BGP (cont’d.)
• Internet reorganized into a multitier structure
• Autonomous System (AS)
– Top tier
– One or more networks governed by a single
dynamic routing protocol within that AS
– Does not use IP address, but rather uses a globally
unique Autonomous System Number (ASN)
assigned by IANA
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.29 The Internet
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.30 Configuring a Cisco router to use an ASN
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
BGP (cont’d.)
• Autonomous Systems communicate with each
other using an Exterior Gateway Protocol
(EGP)
• Network or networks within an AS
communicate with Interior Gateway Protocols
(IGPs)
• Neither of these are dynamic routing
protocols
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
BGP (cont’d.)
• Many protocols are used within Autonomous
Systems, such as RIP
• The Internet uses one protocol for
communication between each AS: the Border
Gateway Protocol (BGP)
– Current version: BGP-4
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Connecting Autonomous Systems
• BGP listed by CompTIA as a hybrid routing
protocol; more technically a path vector
routing protocol
• Has different types of routing tables
– Routers are manually configured
• Advertise information passed to them from different
Autonomous Systems’ edge routers
– Forwards advertisements that include the ASN
and other non-IP information
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Connecting Autonomous Systems
(cont’d.)
• BGP handles tasks unique to the Internet
• Most BGP routers will ignore unreliable routes
• BGP supports policies that ISPs can use to limit
who and how other routers may access them
• BGP supports route aggregation
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Link State
• Dynamic routing protocol that announces and
forwards individual route changes as they
occur
• Only two link state dynamic routing protocols:
– Open Shortest Path First (OSPF)
– Intermediate System to Intermediate System
(IS-IS)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Open Shortest Path First (OSPF)
• Most commonly used IGP in the entire
Internet
• Designed to work within a single AS
• Converges dramatically faster than RIP
• Complex protocol for routers
– Not found on cheap home routers
– Requires a great deal of computational power
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
• First launch of an OSPF-capable router
– Router sends out link state advertisements (LSAs)
called Hello packets
• Looking for other OSPF routers
– Sends out lots of LSA Hellos on first boot
(flooding), and periodically thereafter
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.31 Hello!
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
• OSPF cost formula
– 100,000,000 / bandwidth in bps
• A 10BaseT link’s OSPF cost is:
100,000,000 / 10,000,000 = 10
– The faster the bandwidth, the lower the cost
– Can be overridden manually
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.32 Link states
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
• OSPF routers exchange information and
update their link state databases
• LSA Hellos forward to every OSPF router
• Within a few seconds, every router knows the
link state for every other router
• Routers can be grouped into areas
– With multiple areas, the central area is the
backbone
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
•
•
•
•
The backbone has an Area ID of 0
Area border routers (ABRs) interconnect areas
OSPF areas almost instantly gain convergence
After convergence, each router in
the area sends Hello LSAs about every 30
minutes
• OSPF routers also keep alternate routes to the
same network ID
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.33 Area defined
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
• OSPFs popularity
– Scales to large networks quite well
– Supported by nearly all routers
– Supports authentication
– Shortest-path-first method prevents loops
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
• If link breaks between routers A and B:
– Routers A and B detect the break
– Each router attempts to reconnect
– After a few seconds of failures, router sends out
an LSA announcing the broken link
– Only sends single changed route, not the
entire table
– Each router updates its routing table
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.34 Announcing a disconnect
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
OSPF (cont’d.)
• OSPF’s popularity
– Scales to large networks
– Supported by all but the most basic routers
– Supports authentication
– Shortest-path-first method prevents loops
• Until recently OSPF did not support IPv6
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Intermediate System to Intermediate
System (IS-IS)
• A link state dynamic routing protocol
• Similar to OSPF
• Applies the concept of areas and sending only
updates to routing tables
• Worked with IPv6 from the start
• The de facto standard for ISPs
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Enhanced Interior Gateway Routing
Protocol (EIGRP)
• Proprietary to Cisco
• Developed to replace RIP before OSPF
• An advanced distance vector protocol
– Includes aspects of both distance vector and link
state protocols
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Dynamic Routing Makes the Internet
• The Internet depends on dynamic routing for
self-healing
• Manual updating static routes would be
impossible with so many routes
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Route Redistribution
• A router takes routes it has learned by one
method, say RIP or a statically set route, and
announces those routes over another protocol
such as OSPF
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Working with Routers
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Working with Routers
• Simple physical installation
– Home router
• Give it power
• Plug in connections
– Business-class router
• Insert it into a rack
• Give it power
• Plug in connections
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Connecting to Routers
• Each router must be configured
• Yost (or rollover) cable
– One of the oldest methods for connecting to a
router
– A special serial connection
– Almost unique to Cisco-brand routers
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.35 Cisco console cable
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Terminals and Consoles
• Switches can also be configured
• Managed devices
– Routers and advanced switches
• Plug the rollover cable into the console port
on the router and a serial port on a PC
– Use USB-to-serial adapter if no serial port is
available
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.36 Console port
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Terminals and Consoles (cont’d.)
• Use a terminal emulation program to talk to
the router
– Popular programs: PuTTY and HyperTerminal
• Serial port settings
– 9600 baud
– 8 data bits
– 1 stop bit
– No parity
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.37 Configuring PuTTY
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Terminals and Consoles (cont’d.)
• Once you are connected and running the
terminal emulator
– You will see the initial router prompt
– Working with IOS commands
•
•
•
•
Type enable and press ENTER
The prompt changes to Router#
IOS is complex
Newer CISCO routers will lead you through the initial
configuration for basic setup
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.38 Initial router prompt
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Web Access
• Most routers have a built-in Web server
– Easy to use and enables all functions
• Router must have a built-in IP address
– Use a laptop and a crossover cable
– Set a static address for the computer to place the
PC on the same network ID as the router
– Connect to the router and type in the IP address
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.39 Default IP address
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.40 Entering the IP address
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.41 User name and password
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Management Software
(NMS)
• Advanced tool that describes, visualizes, and
configures an entire network
– Usually available as a Web site for network
administrators
• Types of NMS
– Proprietary tools
– Third-party tools
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.42 Cisco Network Assistant
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.43 OpenNMS
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Other Connection Methods
• Most routers have more than one way
to connect
• Many home routers have a USB port and
configuration software
• More powerful routers may allow connection
with Telnet protocol or newer Secure Shell
(SSH)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Basic Router Configuration
• Must have at least two connections
• Must properly configure every port on a
router to talk to connected network IDs
• Make sure the routing table sends packets to
the intended destination
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.44 The setup
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Setup (Example in Figure 8.44)
• Step 1: Set up the WAN side
– The WAN side in a home or a small business
router connects to an ISP
– Get setup information from the ISP
– Most home routers use DHCP on the WAN side
and just need to be configured to use DHCP
– Static IP address: follow instructions from the ISP
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.45 WAN router setup
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.46 Entering a static IP
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Setup (cont’d.)
• Step 2: Set up the LAN
– You have total control over the LAN side of the
router
– Choose a network ID from the private range
– Assign the correct IP information to the LAN-side
NIC
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.47 Setting up an IP address for LAN side
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Setup (cont’d.)
• Step 3: Establish routes
– The router will usually build a routing table based
on information you provided
– You may add more routes if needed
– Use IOS command line on Cisco routers
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Setup (cont’d.)
• Step 4 (optional): Configure a dynamic
protocol
– Dynamic routing protocols are tied to individual
NICs
– When you connect two routers together, make
sure the NICs are configured to use the same
dynamic routing protocol
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Document and Back Up
• Document the steps completed to configure
each router
• Back up the configuration
– Every router provides a backup method
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Troubleshooting Router Problems
• Consider non-router issues first
– Routers don’t fail very often
• What is your router is supposed to do?
– Does it just route traffic?
– Does it also perform NAT?
– Is routing failing, or is another function failing?
• Know how to use basic tools to check the
router: traceroute commands vary by OS
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
traceroute
• Tells you when things are not working
• Gives you an idea of where to look for a
problem
• Windows – tracert; UNIX/Linux –
traceroute
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Other Tools
• My traceroute (mtr)
– Similar to traceroute
– Dynamic, continually updates the route selected
for monitoring
– Linux tool
• Window provides pathping
– Computes the performance over a set time
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 8.48 mtr in action
Copyright © 2015 by McGraw-Hill Education. All rights reserved.