Table of Contents for
Packet Tracer Network Simulator

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Packet Tracer Network Simulator by Jesin A Published by Packt Publishing, 2014
  1. Cover
  2. Table of Contents
  3. Packet Tracer Network Simulator
  4. Packet Tracer Network Simulator
  5. Credits
  6. About the Author
  7. About the Reviewers
  8. www.PacktPub.com
  9. Preface
  10. Who this book is for
  11. Conventions
  12. Reader feedback
  13. Customer support
  14. 1. Getting Started with Packet Tracer
  15. Installing Packet Tracer
  16. Interface overview
  17. Creating a simple topology
  18. Summary
  19. 2. Network Devices
  20. Customizing devices with modules
  21. Emulating WAN
  22. Accessing the CLI
  23. Summary
  24. 3. Generic IP End Devices
  25. Servers
  26. Other end devices
  27. Configuring end devices
  28. Summary
  29. 4. Creating a Network Topology
  30. Testing connectivity with PDUs
  31. Using the simulation mode
  32. Clustering a topology
  33. Summary
  34. 5. Navigating and Modifying the Physical Workspace
  35. Moving devices physically
  36. Managing cables and distances
  37. Customizing icons and backgrounds
  38. Summary
  39. 6. Configuring Routing with the CLI
  40. Dynamic routing protocols
  41. The Routing table
  42. Load sharing
  43. Summary
  44. 7. Border Gateway Protocol (BGP)
  45. BGP versus dynamic routing protocols
  46. Configuring BGP in Packet Tracer
  47. Summary
  48. 8. IPv6 on Packet Tracer
  49. IPv6 static and dynamic routing
  50. Using both IPv4 and IPv6
  51. Summary
  52. 9. Setting Up a Wireless Network
  53. Wireless networks and physical workspaces
  54. Summary
  55. 10. Configuring VLANs and Trunks
  56. InterVLAN routing with routers and layer 3 switches
  57. Switch-to-switch trunk links
  58. Analyzing broadcasts in the simulation mode
  59. Summary
  60. 11. Creating Packet Tracer Assessments
  61. The initial network
  62. The answer network
  63. Testing the activity
  64. Summary
  65. Index

Configuring BGP in Packet Tracer

First, let's look at the commands used in BGP:

router bgp <asn>

For example:

R1(config)#router bgp 120

This command enables BGP on a router and moves to the router configuration mode. The ASN can be any value between 1 and 65535. Once enabled, the BGP process must choose a router ID. By default, BGP uses the following methods priority-wise, to pick a router ID.

  • Configured: This is the router ID configured by using the bgp router-id router subcommand
  • Highest loopback: This is the highest numeric IP address configured on any up loopback interface at the time the BGP process is initialized
  • Highest other interfaces: This is the highest numeric IP address configured on any up non-loopback interface at the time the BGP process is initialized

A router ID can be explicitly configured using the following command:

bgp router-id X.X.X.X

For example, we can use the following command to configure the router ID:

R1(config-router)#bgp router-id 1.1.1.1

For configuring a BGP neighbor, we can use the following command:

R1(config-router)#neighbor X.X.X.X remote-as <asn>

For example:

R1(config-router)#neighbor 10.0.0.2 remote-as 130

The ASN entered for remote-as should be the ASN of the neighboring router. This changes in eBGP and is the same in iBGP. Let us look at an example.

The following commands are used to change the eBGP:

R1(config)#router bgp 120
R1(config-router)#neighbor 10.0.0.2 remote-as 130

The following commands are used to change the iBGP:

R1(config)#router bgp 120
R1(config-router)#neighbor 192.168.1.20 remote-as 120

As mentioned earlier, when exchanging routes within an AS, iBGP doesn't modify the next-hop field. This can become problematic because the next hop is the IP of the neighboring AS's router, and unless it is redistributed by using an IGP, the internal network will reject the routes because the next hop is invalid. So, the following command sets its own IP as the next-hop of a route:

R1(config-router)#neighbor X.X.X.X next-hop-self

BGP also has a network command. This is used to specify a route that will be advertised in BGP. This route should exist in the routing table to be advertised in BGP:

R1(config-router)#network 10.20.20.0 mask 255.255.255.0

It is also possible to omit the mask command, doing which it takes the network as a classful one.

There are a lot of other commands in BGP that Packet Tracer doesn't support, so we'll go ahead and configure a topology using these commands.

For this exercise, we'll use a single mutihomed design (shown in the following screenshot) as Packet Tracer doesn't support iBGP:

Configuring BGP in Packet Tracer

This topology has four routers—two belonging to different enterprises and the other two belonging to different ISPs. Both the enterprise routers have loopback interfaces configured with the IP addresses shown in the topology. This is to demonstrate the injecting of routes into BGP.

The following table lists the interfaces and their IP addresses:

Device

Interface

IP address / Subnet Mask

Enterprise1

Loopback0

20.30.0.1 / 255.255.0.0

 

FastEthernet0/0

10.0.0.1 / 255.255.255.252

 

FastEthernet1/0

10.0.0.9 / 255.255.255.252

Enterprise2

Loopback0

40.30.0.1 / 255.255.0.0

 

FastEthernet0/0

10.0.0.5 / 255.255.255.252

 

FastEthernet1/0

10.0.0.13 / 255.255.255.252

ISP1

FastEthernet0/0

10.0.0.2 / 255.255.255.252

 

FastEthernet1/0

10.0.0.6 / 255.255.255.252

ISP2

FastEthernet0/0

10.0.0.10 / 255.255.255.252

 

FastEthernet1/0

10.0.0.14 / 255.255.255.252

The following are the steps to configure BGP on the meshed network topology:

  1. Let's start configuring BGP on the enterprise routers:
    Enterprise1(config)#router bgp 10200
Enterprise1(config-router)# bgp router-id 0.0.0.1
Enterprise1(config-router)#neighbor 10.0.0.2 remote-as 30200
Enterprise1(config-router)# neighbor 10.0.0.10 remote-as 50300
Enterprise1(config-router)# network 20.30.0.0 mask 255.255.0.0

Enterprise2(config)#router bgp 3400
Enterprise2(config-router)# bgp router-id 0.0.0.2
Enterprise2(config-router)#neighbor 10.0.0.6 remote-as 30200
Enterprise2(config-router)# neighbor 10.0.0.14 remote-as 50300
Enterprise2(config-router)# network 40.30.0.0 mask 255.255.0.0
  2. Now let's configure the ISP routers:
    ISP1(config)#router bgp 30200
ISP1(config-router)# bgp router-id 1.1.1.1
ISP1(config-router)# neighbor 10.0.0.1 remote-as 10200
ISP1(config-router)# neighbor 10.0.0.5 remote-as 3400
ISP2(config)#router bgp 50300
ISP2(config-router)# bgp router-id 2.2.2.2
ISP2(config-router)#neighbor 10.0.0.9 remote-as 10200
ISP2(config-router)# neighbor 10.0.0.13 remote-as 3400
  3. You should now see console messages indicating that a BGP neighbor is up:
    %BGP-5-ADJCHANGE: neighbor 10.0.0.9 Up
%BGP-5-ADJCHANGE: neighbor 10.0.0.13 Up
  4. Now try pinging from Enterprise1 to the loopback address of Enterprise2:
    Enterprise1>ping 40.30.0.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 40.30.0.1, timeout is 2 seconds:
Success rate is 0 percent (0/5)
  5. We see that it fails. This is because the ICMP request packet uses a source address of 10.0.0.1, so when this packet is received by Enterprise2, it doesn't have a route to 10.0.0.0/30 for sending a reply. We used the network command to inject only the routes of loopback addresses, hence we shall use the source address of the loopback itself using an extended ping:
    Enterprise1>enable
Enterprise1#ping
Protocol [ip]:
Target IP address: 40.30.0.1
Extended commands [n]: y
Source address or interface: loopback0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 40.30.0.1, timeout is 2 seconds:
Packet sent with a source address of 20.30.0.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 62/62/63 ms
  6. So, we have successfully configured eBGP. Let us take a look at the routing table of BGP:
    Configuring BGP in Packet Tracer

    If you look at the Path column, you can see the ASNs that come in the path to the destination. The > symbol indicates a preferred route.