1. Routing
Chapter 7

2. objectives Upon completion of this chapter, you should be able to:
Configure a router with basic settings
Describe the routing process
Read a routing table
Configure static & default routes
Describe routing protocols RIP, EIGRP, OSPF
Configure OSPF
Describe NAT
Configure NAT & Port Forwarding

3. Router interfaces WAN Serial Ports in slot LAN interfaces LAN
Interfaces in slot
Console
Port RJ45
Console & AUX are management ports. Out-of-band management. AUX is for dial-up modem connection.
Each Ethernet & Serial interface is a separate network.
Ethernet usually connects to switches; Serial usually connects to ISP/other routers.
Can access CLI of router through CON, AUX, or Telnet/SSH.
AUX
Port RJ45

4. 7.1
Routing basics

5. What is routing? Moves packets from one network to another
Finds the best path to destination based on destination IP & SM
Checks its routing table
Routing table has destination networks and the port to go out to reach that network.

6. Routing table & routes Router knows its directly connected networks
Router learns of remote networks
To send to another network, explain Proxy ARP again.
Source uses the router port’s MAC as the temporary destination MAC.
Router reads the destination IP & SM & looks in routing table for that network. (Says the network is available by going out port e1 towards IP (next hop IP).
E1’s MAC address is substituted in the Destination MAC address.
Packet gets to next router, looks in routing table, sees the destination network is directly connected, checks its ARP table on e0, subs the real destination MAC in, and sends it out port e0.

7. How to get in the routing table
Directly connected- YOU’RE IN!
Remote networks- LEARN IT!
Static entry- YOU TYPE IN
Dynamic entry- ROUTING PROTOCOL EXCHANGES INFO BETWEEN ROUTERS
After it learns all routes IN your network-
Converged!
Static- stays in until you change it. If network changes, you have to remember to change the entry.
Dynamic- learns automatically and will change automatically when the network changes.

8. default routes How do you get OUT of your network?
Create a default route (special static route)
For default route, use quad zero
IP SM
Means ANY
No default route= Most likely no communication outside your network

9. Configure a Default Route
Router forwards packet to a destination network
Looks at routing table to see which port to go out
You can set a default route to go out if destination network is not in routing table
Usually used when you only have one path out. Saves the router from thinking or ANDing/processing.
IP route quad zero (IP/SM) next hop IP or outgoing interface

10. Configure default route
Default route using outgoing next hop IP
Default route using outgoing INT
Give the serial ports IP address before this example is done.

11. Routing table Show ip route How it was learned When it was updated
Stored in RAM
How it was learned
When it was updated
Which interface to use to get to that network

12. Parts of routing table
These show DIRECTLY CONNECTED & LOCAL LINK (THE ACTUAL INTERFACE ON THE ROUTER)

13. ROUTING TABLE- OTHER NETWORKS
No destination network/next hop….packet is dropped.
You can configure a default route, basically saying “I don’t know but go to this next router, maybe they know.”

14. PC1 to PC4. Check the routing table.
R1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
/8 is variably subnetted, 2 subnets, 2 masks
D /24 [90/ ] via , 00:00:05, Serial0/0/0
D /24 [90/ ] via , 00:00:05, Serial0/0/0
/24 is variably subnetted, 2 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/0
L /32 is directly connected, GigabitEthernet0/0
/24 is variably subnetted, 2 subnets, 3 masks
C /24 is directly connected, GigabitEthernet0/1
L /32 is directly connected, GigabitEthernet0/1
/24 is variably subnetted, 2 subnets, 3 masks
C /30 is directly connected, Serial0/0/0
L /32 is directly connected, Serial0/0/0
R1#
/24 R2
/24
/24
/24
/30
.226
.10 .1
G0/1
.225
S0/0/0
G0/0 R1
PC1
PC2
PC1 to PC4. Check the routing table.
PC2 to comcast.net at
NOTE: default route is not set.

15. Review- 4q
What do you configure in a router to tell it “if you don’t have the destination network in the routing table, go this way.”
Default route
What are the 2 possible commands to configure a default route?
B(config)# ip route next hop IP
B(config)# ip route outgoing int
What does the quad zero mean?
Any network (IP/SM)
Which command encrypts all passwords?
Service password-encryption

16. Static route You telling the router:
“To get to this network, go this way!”
Used so routers do less “thinking” or when there’s only one way out of a network
Stub networks or small networks
Same as default route config, but replacing quad zero with destination network address

17. Configuring the Static Route
ip route destination_network subnet mask next hop ip or outgoing int
R1(config) #ip route
Generally static routes are used on small networks, not large ones. You’d have too many static routes to maintain.
A static route’s AD would be 1.
ANSWER: ip route or
Ip route s0/0/1
What would be the static route on R2 to reach the ladies’ network?

18. activity TestOut 7.1.1- Routing TestOut 7.1.3- Practice Questions (5)
TestOut Configure Static Routes
Handout: Create static routes
Complete the PT lab together
Configure default and static routes

19. 7.2
Routing protocols

20. Autonomous system Each private network is identified by an AS #
Given by your ISP

21. Types of routing protocols
They share routing information
IGP (Interior Gateway Protocol)
Shares routing info WITHIN the AS
Most common you’ll work with
EGP (Exterior Gateway Protocol)
Shares routing info BETWEEN AS
Internet routing

22. Choosing the best path Metrics Method of choosing the best path
Hops, throughput, delay, load, reliability, etc.
Lowest metric- best route!
Animation 1: Hop Count
Animation 2: Bandwidth/Delay; Also compare to hop count (100’s & 10’s are metric numbers assigned. Lowest metric preferred).
There are default metric values for each routing protocol. Metrics for each type of routing protocol can be changed in configuration, if you want. You would do this to force using a particular route.

23. Categories of routing protocols
Distance Vector
Link-State

24. Dynamic routes: Distance vector Routing protocols
7.2.1
Dynamic routes: Distance vector Routing protocols

25. Dynamic Routing Protocols
Maintain tables when changes occur
Bad cables, interfaces go down, better route learned
Best route to a network in table
Removes routes when no longer valid
When all routers agree on topology= converged
Two routers can exchange these tables as long as they use the same protocol

26. Distance Vector Routing
Passes updates every so often to connected neighbors
Distance & Direction
Metric (hops, speed, reliability, etc)
DV: Shares routing tables with neighbors. Exchanges info a certain intervals (example: every 30 seconds).

27. Distance Vector Routing update metric
Directly connected network has an administrative distance of 0
Neighbors update each other & add on how far away it is
Star is 2 away
Star is 1 away
Star is 0 away
Star is 2 away

28. activity Handout Create a Diagram from Routing Tables
Distance Vector Routing Tables Using Hops
Do together on SmartBoard
Create a Diagram from Routing Tables
On paper
In groups of 2, create a topology based on Routing Table
End of Day One

29. Dynamic routes: link state Routing protocols
7.2.1
Dynamic routes: link state Routing protocols

30. Link state routing
Link-state routing protocols are like your navigation system, they have a complete map of the network. If you have a full map of the network you can just calculate the shortest path to all the different destinations out there. This is cool because if you know about all the different paths it’s impossible to get stuck in a loop since you know everything! Read more:

31. Link state routing
Link-state routing protocols operate by sending link-state advertisements (LSA) to all other link-state routers.
All the routers need to have these link-state advertisements so they can build their link-state database or LSDB. Basically all the link-state advertisements are a piece of the puzzle which builds the LSDB.
LSAs get flooded to all routers.
Each router ends up with all of the pieces of the puzzle, which is part of its Link State Database.
The LS Database is like having a map of your country.
Once every router has a complete map of the network, it calculates the shortest path to each destination.
The BEST path to each destination goes into the routing table.
Calculating the shortest path is like using your navigation system, it will look at the map and look at all the different ways of getting to the destination and only show you the best way of getting there.

32. Link State Routing review
Knows all routes in your network
Sends out LSAs at start
Makes a Topological database
With info from LSAs
Uses the SPF algorithm
Each change causes new calc & database update
Map of network from point of view of the router
Info in tree is used to build the routing table
Adds best path to each destination to routing table
Then only sends change updates
Less chatty than DV.

33. Others Hybrid Using VLSM in your network? No subnet mask info sent?
Uses both DV & LS
Using VLSM in your network?
Most current routing protocols send subnet mask info
They are called Classless Routing Protocols
No subnet mask info sent?
These are called Classful Routing Protocols

34. rip: distance vector Routing protocol
7.2.3
rip: distance vector Routing protocol

35. rip DV IGP Metric is Hops Updates every 30 seconds by default
Only15 Max; 16 is unreachable (D)
Updates every 30 seconds by default
Sends entire routing table (D)
If change, update sent immediately (triggered)
Slow to converge whole network (D)
Administrative Distance is 120
The (D) is a disadvantage.
RIP is okay for small networks.
Older.

36. RIP RIPv1 RIPv2 Doesn’t send subnet mask in updates
Classful subnetting
RIPv2
Classless (VLSM) subnetting
Supports authentication
Otherwise, same as v1

37. RIP
By entering router rip & its networks, you are telling the router to advertise these networks to it directly connected neighbors so they know how to get to these networks.

38. Configure RIP Router(config)#router rip
Router (config-router)#version 2
Router(config-router)#network network-number
Tells which networks to advertise!

39. Verifying RIP Ping Show ip route Show ip protocols Debug ip rip
Make sure to turn debugging off! It creates constant traffic.

40. Show ip protocols output

41. Disadvantages of RIP Increased traffic every 30 seconds
Max hop count of 15
Further away is unreachable
Only considers hops, not speed
Possible routing loops

42. activities Configure RIP PT Lab Configure & Verify RIP
In groups of 2, using the handout
PT Lab Configure & Verify RIP
Use our in class PT lab to configure RIP & verify it.
RIP Homework

43. Review- 5q
What routing protocol uses hops for its metric and understands classless routing?
RIPv2
What is the AD of RIP?
120
What’s the purpose of entering your router’s network numbers when configuring RIP?
To tell it what networks to advertise in updates
A directly connected network has an AD of…
A static route has an AD of… 1

44. eigrp: hybrid Routing protocol
7.2.3
eigrp: hybrid Routing protocol

45. EIGRP Enhanced Interior Gateway Routing Protocol
Hybrid IGP (mix LS & DV)
AD of 90
Many metrics (bandwidth, delay, load, reliability)
Up to 255 hops
Updates on start of router & only when a change happens
VLSM Support
In 2013, Cisco made it an open standard.
Hops is not a metric used.

46. ospf: link state Routing protocol
7.2.3
ospf: link state Routing protocol

47. ospf Most popular routing protocol LS IGP AD of 110
Sends updates only when the topology changes
Does not send periodic updates of the entire routing table
AD of 110
Metric is cost (bandwidth)
Fast convergence, no loops
Supports VLSM/classless addressing

48. Ospf areas OSPF works with the concepts of areas
Keeps the map of network smaller if you break it up into areas
By default you will always have a single area
Normally this is area 0
You can have multiple areas
They all connect to area 0 (the backbone)
See picture…
So why do we work with areas? Remember what I just explained about your navigation system. If you tell your navigation system to calculate from New York to Los Angeles it will take much longer than calculating a route from one street to another street in the same city. This calculating is called the shortest path first or SPF algorithm and the same thing apply to OSPF. Our routers only have a full picture of the network topology within the area, the smaller your map the faster your SPF algorithm works!

49. Configure a router and ospf
7.2.3
Configure a router and ospf

50. Configure the network
Set up a PC with a console connection to the Student Center Router.
Use Auto cable selection between routers.

51. Configure the router Configure StudentCenter Router:
Hostname- StudentCenter
Enable password- cisco
Secret password- class
Con 0 & vty password- gcit
Encrypt all passwords
Se0/0/ /24
Se0/0/ /24
Configure ScienceBuilding Router
Configure AdminBuilding Router

52. Sample configuration

53. Configure Ospf ScienceBuilding(config)#router ospf 1
ScienceBuilding(config-router)#network area 0
ScienceBuilding(config-router)#network area 0
AdminBuilding(config)#router ospf 1
AdminBuilding(config-router)#network area 0
AdminBuilding(config-router)#network area 0
Also configure StudentCenter
Process ID
Wildcard mask
The 1 is the process ID and can be anything & each one could have something different. Be consistent.
The wildcard mask is the opposite of the subnet mask. 0 means match, 1 means ignore.

54. Wildcard mask
Think of a wildcard mask as the inverse of a subnet mask.
The inverse of the subnet mask is
To calculate the inverse of the subnet mask, subtract the subnet mask from :
– Subtract the sm
Wildcard mask

55. Verify routing table StudentCenter#Show ip route
Views the routing table

56. verify StudentCenter#show ip ospf neighbor
AdminBuilding#show ip protocols
AdminBuilding#show ip route ospf
FULL means it’s done exchanging info.
Note the routing table entry:
O=OSPF
Destination network
110- administrative distance/2-cost
Via- next hop IP
Outgoing interface

57. bgp: exterior Routing protocol
7.2.3
bgp: exterior Routing protocol

58. bgp Border Gateway Protocol Exterior gateway protocol
Used for sharing routes on the Internet
Supports VLSM

59. activity TestOut 7.2.7- Enable OSPF Routing
TestOut Practice Questions (15)

60. Nat: network address translation
7.3
Nat: network address translation

61. nat Allows you to save public IP addresses
Use private inside your network
Use one/few public for outside access
Used on your border/gateway router
Home & school
A: range
B: range
C: range
CLASS
PRIVATE IP ADDRESS RANGE A B C

62. Nat simply explained
Inside devices have a private, non-routable IP address.
Your router’s WAN port has a public IP address assigned by the ISP.
Your router uses NAT to allows the private devices to communicate publicly.
It translates the private to the given public IP to send stuff out, and then it re-translates it for stuff coming into the network back to your device.
NAT is NOT a firewall, only a translator.

63. Types of nat Static NAT PAT/NAT Overload
One to one mapping; AKA Port Forwarding
A particular INSIDE PRIVATE IP always translates to the SAME PUBLIC IP
Use: Server on the inside that outside people need to access
PAT/NAT Overload
Port Address Translation
Many-to-one mapping
Many INSIDE PRIVATE IP’s translated to ONE PUBLIC (most common at home)
Keeps track using source port #’s
To understand how port forwarding works and what it accomplishes, think of a front desk at a hotel. When a letter addressed to a customer care of the hotel arrives, the front desk looks up the room number of the customer and sends the letter to that room. Similarly, once your router has been configured for Port Forwarding, it will look at the "customer name" (port number) attached to each "letter" (incoming access) and forward it to the appropriate "room number" (IP address).

64. Types of nat Dynamic NAT Many to many mapping
Has a pool of public IP addresses to choose from
More for getting out rather than getting in
Translates the private IP to one of the public IPs & awaits a response
After session is closed, the public IP is returned to the pool of public addresses

65. Static nat example

66. Static nat example 2 Security camera network.
Access the cameras from the outside.

67. Pat / nat overload

68. Dynamic NAT

69. Review- 2q
Which type of NAT maps many private IP addresses to one public IP, like in your home network?
PAT or NAT Overload
You have a web server at work hosting your work website. It’s behind your firewall & has a private IP address. Which type of NAT will allow people outside of your network to access it?
Static NAT

70. Configuring static nat
7.3.2
Configuring static nat

71. Configure static nat Set the static map addresses
Tell the router which port is the inside side
Tell the router which port is the outside side

72. Configuring port forwarding
7.3.4
Configuring port forwarding

73. Port forwarding linksys
Your device MUST have a static IP address
Example:
You have an IP camera
You want to access it from anywhere
Assign it
Use port forwarding to allow communication to go through only using a certain port
Do this in Packet Tracer
Add WRT300 in Wireless Devices
Applications & Gaming Tab
Port 8090; TCP; for
By setting up Single Port Forwarding, your gaming consoles will have access to the Internet and game servers since this feature allows the router to open specific ports all the time to let requests from a computer in your network to pass through the Internet, and vice versa without any issues.    For you to configure such settings on your router, you must retrieve certain port numbers exclusively assigned to your gaming console. 

74. activity
Packet Tracer - Configuring Port Forwarding on a Linksys Router
TestOut Practice Questions (11)

75. Review- 1q Which statement describes NAT overload or PAT?
Each internal address is dynamically translated to an individual external IP address.
A single internal address is always translated to the same external IP address.
Many internal addresses are translated to a single IP address using different port numbers.
Many internal addresses are statically assigned a single IP address and port. #3

76. Router troubleshooting
7.5
Router troubleshooting

77. What’s wrong? (2) Scenario 1:
One of the PCs cannot communicate with anyone on the local network or the Internet.
Wrong IP on C
Scenario 2:
One of the PCs can communicate with everyone on the local network but not the Internet
Wrong DG on D
NEITHER ARE ROUTING ISSUES.

78. Check the router
The PCs on the network can talk to each other but not outside of the network. You cannot ping outside addresses or the DG.
What could you check? ASK THE STUDENTS TO LIST THINGS:
Cable from switch to router (is it correct kind/straight through; is it plugged in; is it plugged into the correct port; is it damaged)
Port E0 on the router (is it enabled [no shutdown]; correct ip/sm configured)

79. Check the router 2
The PCs on the network can talk to each other but not outside of the network. You CAN ping the DG.
What could you check? ASK THE STUDENTS TO LIST THINGS:
Can you ping the E1?
Can you ping the S0?
Is routing enabled? Like RIP/EIGRP/OSPF
Is routing configured correctly? Area 0; correct network numbers/wildcard mask; use show run, show start, show ip route
Are the serial cables to the other routers connected/shutdown? Use show int/show ip int brief
Check the routing table (show ip route) to see if there’s a route learned to that network
Is there a default route configured to get out if there is no route in the table

80. Use ping and traceroute
Try and ping to see if you can get to it or not,
Then try a tracert (traceroute in the router) to see WHERE the problem is. In this example, the problems seems to be past the top router. That’s where it timed out.

81. activity TestOut 7.5.4- Find Path Information 1

82. Review & study Complete the study guide handout Complete TestOut
Practice in Packet Tracer
Jeopardy review

83. Routing
Chapter 7