Download Devices & Internet - The Computer Engineers` Blog

Planning and
Troubleshooting Routing
and Switching
Overview
Selecting Intermediate Devices
Planning an Internet Connectivity Strategy
Planning Routing Communications
Troubleshooting TCP/IP Routing
Lesson: Selecting Intermediate Devices
Types of Devices
When to Use Routing
Types of Networking Domains
What Are the Features of Switches?
Virtual LANs
Full-Duplex Transmission in Switched Environments
Guidelines for Selecting an Appropriate Intermediate
Device
Types of Devices
Device
OSI layer
Hub
Physical
(layer 1)
Switch
Data-link
(layer 2)
Router
Network
(layer 3)
Layer 3
switch
Network
(layers 2 and
3)
Definition
Extends the network by retransmitting the signal
Does not process the data
Is invisible to the nodes
Forwards frames according to the destination
address
Uses temporary or virtual connections to connect
source and destination ports
Used to link WANs and dissimilar LANs
Operates at the packet level
Sends packets based on packet addressing
Is a limited-purpose hardware-based IP router
with bridging capabilities
Also performs layer 2 switching
When to Use Routing
Use routing to:
Isolate networks from each other
Provide a start for a secure network implementation
Traditional uses of routers
Connecting WANs
Segmenting LANs
Types of Networking Domains
Broadcast Domain
Segment A
Segment B
Switch
Hub
Collision Domain A
Hub
Collision Domain B
What Are the Features of Switches?
Switch feature
Layer 3
Cost
Hardware routing
Benefits
Routes packets at layer 3
Forwards frames at layer 2
Substantially cheaper than similar
performance routers
Fast performance (near wire speed)
Minimal latency
Virtual LANs
Layer 3 Switch
VLAN 1
VLAN 2
Hub
A
B
Hub
C
D
Hub
E
VLAN ABE – Broadcast Domain
F
G
VLAN CDFG – Broadcast Domain
Full-Duplex Transmission in Switched Environments
Switched Environment
Switch
Frame A
Frame B
Frame C
Full-duplex communication
Frame D
Guidelines for Selecting an Appropriate Intermediate
Device
Cost
Ease of implementation
Administration and troubleshooting sophistication
Protocol support
Layer 1 support
Speed
Functionality
Programmability
Planning an Internet Connectivity Strategy
Requirements for an Internet Connectivity Solution
NAT as a Solution for Internet Connectivity
ISA (Proxy) as a Solution for Internet Connectivity
Guidelines for Planning an Internet Connectivity Strategy
Requirements for an Internet Connectivity
Solution
Internet connectivity requirements
Scalability and fault tolerance
Filtering
User access
Authentication
Bandwidth control
Time-of-day access
Extensibility and flexibility
Application connectivity
NAT as a Solution for Internet Connectivity
Why NAT is a good solution
 Same security requirements for all users
 Non-routed private network
 Required private addressing
131.107.0.9
10.10.10.6
131.107.0.9
10.10.10.10
10.10.10.7
NAT Table
10.10.10.0 maps to
131.107.0.9
ISA (Proxy) as a Solution for Internet Connectivity
Why ISA (Proxy) is a good solution
 Secure Internet and private network access
 Routed or non-routed network
 Cache web contents
131.107.0.9
131.107.0.9
Intranet
10.10.10.10
10.10.10.9
10.10.10.8
10.10.10.8
ISA (Proxy) Server
10.10.10.7
10.10.10.0 maps to
131.107.0.9
Guidelines for Planning an Internet Connectivity
Strategy
Define the existing network structure
Define security requirements
Identify connectivity requirements
Select an appropriate solution
Planning Routing Communications
Determining the Appropriate Connection Method
Selecting a Routing Protocol
Guidelines for Planning Router Connectivity
Determining the Appropriate Connection Method
Connection method
When used
Security is important
Leased lines
Tunneling
Demand-dial routing
On demand
Demand-dial
-persistent
Speed and reliability are required
No budget constraints
Security is important
No modem infrastructure
Security is important
Limited traffic
Per-instance fee pricing structure
Ample traffic
Flat fee pricing structure
Selecting a Routing Protocol
Protocol
Static routes
RIP (dynamic)
OSPF (dynamic)
Criteria
Routing information rarely changes
Small internetworks
Scalability not an issue
Manual updates required
Routing information constantly changes
Automatic routing table updates required
Existing routers use RIP
Design includes demand-dial interface
Maximum number of routers an IP packet will cross is 16
Routing information constantly changes
Existing routers use OSPF
Design includes redundant paths between two subnets
Design has more than 50 subnets
Using IP Packet Filters
Corporate Headquarters
Branch Office
Interface B
outbound
filter
All other
protocols
SNMP
Interface A
inbound
filter
ICMP
All other
protocols
Branch Office
Interface C
outbound
filter
All protocols
Guidelines for Planning Router Connectivity
Identify the router connection method
Determine which connectivity options to use
Determine which routing protocol to use
Identify filter settings
Troubleshooting TCP/IP Routing
How to Isolate a Routing Problem
When to Use Each of the Troubleshooting Tools
Troubleshooting TCP/IP Routing
How to Isolate a Routing Problem
Outside-In Strategy
Can you
ping the
remote host?
Yes
No
Inside-Out Strategy
Can you No Determine
tracert to
where trace
remote host?
fails
Is the IP
configuration
correct?
Is the
routing table
accurate?
Yes
Check system
configuration
Correct the
configuration
Yes
Yes
If problem
still exists,
check route
configuration
No
Can you
access the
failed system?
No
No Correct/delete
the incorrect
route entries
Yes
Can you
ping the
gateway?
No
Contact
network
support
engineer
Yes
Fix
configuration
problem
Contact the
administrator
of the
failed system
Can you
ping interior
gateways?
No
Use tracert
to identify
communication
breakdown
Divide-by-Half : Isolate by ½ the connection issue, then isolate by ½ again
When to Use Each of the Troubleshooting Tools
Troubleshooting area
Utility to use
Hostname
Local computer
configuration
Ipconfig
NetStat
Nbtstat
ARP
Network connections
NetDiag
Tracert
Tracing paths
Ping
Pathping
DNS
NSlookup