cisco certification routers

1. What is a Router?
• A special purpose computer
• Hardware and software dedicated to path
selection and packet switching
• Cisco routers derived from Unix computers

2. Router Capabilities
• Main Functions
– Path selection
– Packet switching
• Additional Functions
– Broadcast containment
– VLAN links
– Security / Access control

3. Router Roles
• Network Edge
– WAN links to other sites in the enterprise
– WAN gateway to Internet
• Network Core
– Backbone links
– Collapsed backbone
• Anywhere
– Network segmentation device
– Security device

4. Router Roles
• WAN links to other sites in the enterprise
– Example: connect Chabot to Las Positas
– Use serial ports
– Low bandwidth, compared to LAN (T-1 is 1.54
mbs)
– Cisco 2500 series router used frequently for this
role.

5. Router Roles
• WAN Gateway to Internet
– Example: connects CLPCCD network to ISP
– Uses serial port
– Low bandwidth, compared to LAN (T-1 is 1.54
mbs)
– Cisco 2500 series router used frequently for this
role

6. Router Roles
• Backbone links
– Connect user groups to backbone
– Use ethernet ports (or other LAN ports such as
token ring or FDDI)
– High bandwidth, (Typically 10 or 100 mbs)
– An older network design
– Cisco modular routers used frequently for this
role (e.g. 3600, 4000 series), but can be done
with 2514 in low traffic situations

7. Router Roles
• “Collapsed Backbone”
– Backbone in a box; center of extended star
– Uses ethernet ports or fast ethernet ports
– A modern network design
– Uses high-end Cisco routers (e.g.7500 series)
– Router often works with large switches to manage
VLANS.

8. Router Roles
• Network segmentation device
– Router links:
• networks
• subnets
• switch VLANS
– Broadcasts (usually) not forwarded
– Router works together with high-end switch (ISL)
or router module is part of the switch

9. Router Roles
• Security device
– Access control rules allow router to control traffic
between:
• networks
• subnets
• switch VLANS
– Traffic regulated by “Access Control Lists”

10. Router Roles
• The Cisco 7507 at the core of Chabot’s net
performs all these roles:
– WAN links to other sites in the enterprise
– Collapsed backbone
– Network segmentation device (VLAN links,
broadcast containment)
– Security device

11. What is this router’s role?
Gateway to Internet

12. What is this router’s role?
WAN link to a remote site in the company
San Francisco
Network
San Jose
Network

13. What is this router’s role?
Backbone access
Science
Dept
Engineering
Dept
Business
Dept

14. What is this router’s role?
“Collapsed Backbone”
Science
Dept
Engineering
Dept
Business
Dept
Administration
Dept
RemoteOffice

15. What is this router’s role?
Network segmentation device
192.168.4.0
net
192.168.5.0
net

16. What is this router’s role?
Network segmentation device
(linking VLANs)
VLAN
1
VLAN
2
VLAN
1
VLAN
2

17. What is this router’s role?
Network segmentation device
(linking VLANs)
VLAN
1
VLAN
2
ISL Trunk
ISL, Cisco’s
Inter Switch Link,
manages traffic
from multiple
VLANs over a
single Ethernet pipe.
ISL is covered in
Semester 3.

18. What is this router’s role?
Security device (firewall)
Access control rules:
1. Outbound traffic to Internet: YES
2. Inbound traffic from Internet: NO

19. Fundamental router design
Routing protocols
Packet forwarding
Control plane
Forwarding plane
(aka data plane)
Router
FIB
RIB

20. Software router
User-level
daemons
routed, OSPFd,
GNU Zebra, Quagga,
XORP
OS kernel &
Network devices
Linux, BSD,
Click,
NetFPGA, IXP

21. Commercial hardware router:
Juniper
Routing Engine (RE)
Packet Forwarding
Engine (PFE)
Control plane
Forwarding plane
Switch Control Board (SCB)
Multi-Services
Module
(MS-PIC)
Multi-Services
Module
(MS-PIC)
• RE
– x86 PC running JUNOS
• PFE
– ASIC hardware and microcode
• MS-PIC
– MIPS64-based XLR network processor
– Each runs separate JUNOS
• JUNOS
– FreeBSD-based OS for all Juniper routers

22. Routers
Modular Fixed
Modular Routers
These type of routers have up gradable slots, and the
number of ports can be increased just by adding cards in
the slots.
Fixed Routers
These types of routers have fixed number of ports.

23. Why Use a Hierarchical Model?
• Reduces workload on network devices
– Avoids devices having to communicate with
too many other devices (reduces “CPU
adjacencies”)
• Constrains broadcast domains
• Enhances simplicity and understanding
• Facilitates changes
• Facilitates scaling to a larger size

24. Hierarchical Network Design
Enterprise WAN
Backbone
Campus A Campus B
Campus C
Building C-1 Building C-2
Campus C Backbone
Core Layer
Distribution Layer
Access Layer

25. Cisco’s Hierarchical Design Model
• A core layer of high-end routers and switches
that are optimized for availability and speed
• A distribution layer of routers and switches
that implement policies and segment traffic
• An access layer that connects users via hubs,
switches, and other devices

26. Router Interfaces
The console port is a management port used to provide out-of-band access to
the router. It is used for the initial configuration of the router, monitoring, and
disaster recovery procedures.
To connect to the console port, a rollover cable and a RJ-45 to DB-9 adapter are
used to connect a PC. Cisco supplies the necessary adapter to connect to the
console port.