1. Introduction to Classless Routing
VLSM
RIP Version 2

2. Introduction to Classless Routing
Variable Length Subnet Masks

3. Classful Routing IP Version 4 provides Classes A, B, C
Limited Number of unique network addresses
Complex Routing tables
No subnet information sent in routing updates by classful routing protocols e.g. RIP v1, IGRP

4. Problem 1a FSF Ltd has been allocated a class C address
It has 3 branch offices with a requirement of 10 hosts per network connecting via point to point links to the Head Office with 25 hosts
Design a subnet mask for FSF
Head Office

5. Problem 1b
FSF Ltd plans
3 additional branch offices (10 hosts per LAN)
Head Office (25 hosts)
Design a new subnet mask

6. Problem 1b continued Variable Length Subnet Mask
Use 27 bit mask for head office (5 host bits = 32 hosts)
Use 28 bit mask for branch offices (4 host bits = 16 hosts)
Use 30 bit mask for router to router links (2 host bits = 4 hosts)
Using write out the addressing scheme for this network

7. Problem 2 Most class A & B network addresses allocated
PHS Ltd with 800 hosts wants IP addresses for its network
4 different Class C network addresses needed
4 routing table entries for that network

8. Solution 2 – Part 1 ISP allocates 212.23.24.0 to 212.23.27.255
Routing table entry for PHS is
/22 OR
22 bit mask in binary:
This mask groups 4 class C networks into 1 network & routing table entry

9. Solution 2 – Part 2 11010100.00010111.00011000.00000000 (Network)
(Mask)
128 64 32 16 8 4 2 1 24
128 64 32 16 8 4 2 1 25
128 64 32 16 8 4 2 1 26
128 64 32 16 8 4 2 1 27

10. Problem 3 PHS Ltd has 4 class C address blocks allocated
It does not want to waste the addresses it has been given
The network administrator has the following requirements based on current use & future growth needs
Head Office hosts Factory - 50 hosts
Logistics Centre – 80 hosts Customer support Centre – 220 hosts
Question:
What is the appropriate VLSM mask solution for PHS Ltd?

11. Solution 3 (example) List the addresses On interfaces On each site
Still available
Head Office
Logistics
Customer Services
Factory
Internet
/22
/30
/30
/30
/23
/24
/26
/25

12. Requirements for classless routing
Classless routing protocol e.g. EIGRP, OSPF, RIP v2
Contiguous network addresses to allow route aggregation

13. Introduction to Classless Routing
RIP Version 2

14. RIP Version 1 Review Supported by most routers
Distance Vector routing protocol
Metric – hop count
15 hop maximum count
Periodic routing updates (30 seconds)
Routing updates broadcast to
Uses holddown timers
Does not send subnet information in updates
Does not support authentication

15. RIP v2 enhancements
Sends subnet information in updates – supports CIDR & VLSM
Supports authentication
Updates multicast to

16. IOS RIP v2 Command Enable RIP v2 Router(config)#router rip
Router(config-router)#version 2
Router(config-router)#network

17. Verifying Routing Protocols
Check the configuration of routing protocols
Router#show ip protocols
Router#show running-config
Viewing RIP updates
Router#debug ip rip

18. Configuring Routes Static Routes Default Route
Router(config)#ip route
ip route destination network gateway
Default Route
Router#ip route
Defines the default gateway for all routes
Keeps routing tables small

19. Default Network
1 router on a network must have a default route on the network e.g.
Router#ip route
Other routers can have a default network set
Router#ip default network
Traffic for destinations outside of the LAN will be sent to the router with the network address

20. Labs 1.1.4 Calculating VLSM Subnets
1.2.3 Review of Basic Router Configuration with RIP
1.2.4 Converting RIP v1 to RIP v2
1.2.5 Verifying RIP v2 Configuration
1.2.6 Troubleshooting RIP v2 using Debug