Please enable JavaScript.
Coggle requires JavaScript to display documents.
R&S C4 : Routing Concepts (4.4 Summary ((cisco routers and cisco…
R&S C4 : Routing Concepts
4.4 Summary
cisco routers and cisco switches have many similarities. They support a similar model operating system, similar command structures , and many of the same commands
one distinguishing feature between switches and routers is the type of interfaces supported by each
the main purpose of a router is to connect multiple networks and forward pacckets from one network to the next. This means that a router typically has multiple interfaces. Each interface is a member or hos on a different IP network
there are many key structures and performance-related characteristics referred to when discussing networks: topology, speed, cost, security, availability, scalability, and reliability
a remote network is a network that can only be reached by forwarding the packet to another router
remote networks are added to the routing table in two ways
by network administrator
manually
implementing a dynamic routing protocol
static routes do not have as much overhead as dynamic routing protocols
however, static routes can require more maintenance if the topology is constantly changing or is unstable
routers make their primary forwarding decision at Layer 3, the Network layer.
However, router interfaces participate in Layers 1,2 and 3.
Layer 3 IP packets are encapsulaed into a Layer 2 data link frame and encoded into bits at Layer 1
router interfaces participate in Layer 2 processes associated with their encapsulation. For example, an Ethernet interface on a router participates in the ARP process like other hosts on that LAN
Components of the IPv6 routing table are very similar to the IPv4 routing table
4.1 Initial Configuration
of a Router
4.1.1 Functions of a Router
4.1.1.1 Characteristics of a Network
Topology
Speed
Cost
Security
Availability
Scalability
Reliabillity
4.1.1.2 Why Routing ?
connect one network to another
4.1.1.3 Routers Are Computers
CPU
OS
Memory and storage
Routers store data using:
Random Access
Memory (RAM)
Volatile
(vluchtig / vervliegend)
Running IOS
Running configuration file
IP routing and ARP tables
Packet buffer
Read-Only Memory (ROM)
Non-Volatile
bootup instructions
basic diagnostic software
limited IOS
Non-Volatile Random Access Memory (NVRAM)
non-volatile
startup configuration file
Flash
non-volatile
IOS
Other system files
4.1.1.4 Routers Interconnect Networks
4.1.1.5 Routers Choose Best Paths
determine the best path to send packets
forward packets toward their destination
(PPP) - Point-to-Point protocol
use routing tables to send packets
use static routes and dynamic roting protocols to learn about remote networks and build their routing tables
4.1.1.6 Packet Forwarding Mechanisms
Process switching
CPU matches destination address with entry in its routing table
Fast switching
fast switching cache to store next-hop information
Cisco Express Forwarding (CEF)
table entries are not packet-triggered like fast switching bu tchange-triggered
4.1.1.7 Activity - Identify Router Components
4.1.1.8 - 4.1.1.9 PT + Lab
4.1.2 Connect Devices
4.1.2.1 Connect to a Network
4.1.2.2 Default Gateways
IP address
Subnet mask
identifies with which network
subnet the host can communicate
Default gateway
identifies the router to send a
packet to when the destination is
not on the same local network subnet
4.1.2.3 Document Network Addressing
device names , interfaces, IP addresses and subnet mask, Default gateways
4.1.2.4 Enable IP on a Host
statically
host manually assigned the
correct IP address, subnet mask, and default gateway
dynamically
IP address information is provided by a server using the Dynamic Host Configuration Protocol(DHCP), dhcp provides valid IP address,subnet mask, defualt gateway
4.1.2.5 Device LEDs
4.1.2.6 Console Access
4.1.2.7 Enable IP on a Switch
ip address information is
configured on a virtual interface
called a switched virtual interface (SVI)
4.1.2.8 Activity
4.1.2.9 PT
4.1.3 Basic Settings on a Router
4.1.3.1 Configure Basic Router Settings
Name of the device
conf t > hostname R1
secure management access
enable secret class
line console 0
password cisco
login
exit
line vty 0 4
password cisco
login
exit
service password encryption
configure a banner
banner motd $ Authorized Access Only! $
save configuratoin
copy running-config startup-config
4.1.3.2 Configure an IPv4 Router Interface
an interface must be
if using IPv4, configured with an address and a subnet mask
Activated
no shutdown
physical layer active
connected to another device
configure the G0/0 interface
interface gigabitethernet 0/0
description Link to LAN 1
ip address 192.168.10.1 255.255.255.0
no shutdiown
exit
configure the serial 0/0/0 interface
interface serial 0/0/0
description Link to R2
ip address 209.165.200.225 255.255.255.252
clock raate 128000
no shutdown
exit
4.1.3.3 Configure an IPv6 Router Interface
only difference is
ipv6 address 2001:db8:acad:3::1/64
4.1.3.4 Configure an IPv4 Loopback Interface
software interface
test device, it is always up
configure the Loopback0 interface
interface loopback 0
ip address 10.0.0.1 255.255.255.0
exitt
4.1.3.5 PT
4.1.4 Verify Connectivity
of Directly Connected Networks
4.1.4.1 Verify Interface Settings
show ip interface brief
summary all interfaces including IPv4 address of interface and status
show ip route
contents of ipv4 routing table
c
connected
l
local
show running-config interfaces
display command configured on specifie dinterface
show running-config interfaces gigabitEthernet 0/0
4.1.4.2 Verify IPv6 Interface Settings
4.1.4.3 Filter Show Command Output
show running-config | section line vty
show ip interface brief
show ip interface brief | include up
show ip interface brief | exclude unassigned
show ip route | begin Gateway
section - include - exclude - begin
4.1.4.4 Command History Feature
terminal historuy size 200
show history
4.1.4.5-4.1.4.6 PT
4.2 Routing Decisions
4.2.1 Switching Packets
Between Networks [ READ THIS STEPS IN THE CHAPTER - NOT COMPLETE]
4.2.1.4 Packet routing
router examines destination MAC address
2.router identifies Ethernet Tyepe field
de-encapsulates the Ethernet Frame
destination IPv4 address of packet does not match any of the interface addresses of router
routing table of router 2 has a route to the desired network with a next-hop IPv4 address and exit interface
IPv4 packet is now encapsulated
into a new data link frame and sent out
when interface is point-to-point(P2P) serial connectoin, the router encapsulates the IPv4 packet into the proper data link frame format used by the exit interface (HDLC, PPP,)
4.2.1.2 Send a Packet
destination IPv4 on same network ?
refers to ARP cache for the MAC address of the device with that destination IPv4 address
mac address no tin cache
generate ARP
determine MAC address
of default gateway , check ARP table
ARP entry not exist in ARP
table for default gateway
send ARP request
router sends ARP reply
not on same network > use default gateway
4.2.1.3 Forward to the Next Hop
router examines destination
MAC address
router identifies Ethernet
type field as 0x800
router de-encapsulates
Ethernet frame
destination IPv4 address of the packet does not match any of the directly connected networks
of Router
4.2.1.5 Reach the Destination
1.router 3 copies data link PPP frame into its buffer
2.router 3 de-encapsulates the data link PPP frame
r3 searches the routing table for the destination IPv4 address of the packet
4.2.1.1 Router switching function
forward packets
to destination
used switching function
step 1 : de-encapsulates the Layer 2
frame header and trailer to expose the Layer 3 packet
step 2 : examines destination ip , to find best ip
step 3 : path found ? encapsulate layer 3 packet into a new layer 2 frame > forwards frame out of exit interface
4.2.1.6 Activity
4.2.2 Path Determination
4.2.2.1 Routing Decisions
Directly connected network
Remote network
forwarded to another router
No route determined
is there a gateway
of last resort set ?
when default route on
router is configured
4.2.2.2 Best Path
multiple paths
use different exit interface
lowest metric is used
as desired path
dynamic protocols with
metrics they use
Routing Information Protocol (RIP)
hop count
Open Shortest
Path First (OSPF)
Cisco's cost based on cumulative
bandwidth from source to destination
Enhanced Interior Gateway
Routing Protocol (EIGRP)
bandwidth,delay , load , reliability
4.2.2.3 Load Balancing
when two are lowest metric cost
then both used sequently
increased effectiveness
and performance
EIGRP supports unequal cost load balancing
4.2.2.4 Administrative Distance
4.2.2.5 Activity - Order the Steps in
the Packet Forwarding Process
4.3 Router Operation
4.3.1 Analyze the Routing Table
4.3.1.1 The Routing Table
Directly connected routes
Remote routes
4.3.1.2 Routing Table Sources
Local Routes interfaes
Directly connected interfaces
Static routes
Dynamic routing protocol
sources of the routing table entries
are identified by a code: how route was learned
L
address assigned to a router's interface,
C
directly connected
S
static route created to reach specific network
D
dynamically learned
network from another
router using EIGRP
O
dynamically learned network form another
router using the OSPF routing protocol
4.3.1.3 Remote Network Routing Entries
Route source
destination network
administrative distance
metric
next-hop
route timestamp
outgoing interface
D 10.1.1.0/24 [90/2170112] via 209.165.200.226, 00:00:05, Serial0/0/0
4.3.1.4 Activity - Interpret the
Content of a Routing Table Entry
4.3.2 Directly Connected Routes
4.3.2.1 Directly connected Interfaces
before interface state is up/up
assigned a valid IPv4 or IPv6 address
activated with no shutdown
receive a carrier signal from another device
4.3.2.2 Directly connected routing table entries
Route source
c
directly
connected network
L
IPv4 address assigned
to the router's interface
Outgoing interface
Destination network
4.3.2.3 Directly connected examples
4.3.2.4 Directly Connected IPv6 Example
4.3.2.5 PT
4.3.3 Statically Learned Routes
4.3.3.1 Static Routes
not auo updated
secure
types of statuc routes
static route to a specific network
code is
s
default static route
similar to default gateway on a hodt
exit point to use when routing table does not contain a path for the destination network
when router only has one
exit point to another router,
when routers connects to a central
router or service provider
4.3.3.2 Static Route Examples
asterisk * in table = means possible
candidate to be the default rotue
4.3.3.3 Static IPv6 Route Examples
4.3.4 Dynamic Routing Protocols
4.3.4.1 Dynamic Routing
share info about reachability and status of the remote network
4.3.4.2 IPv4 Routing Protocols
EIGRP
Enhanced Interior Gateway Routing Protocol
OSPF
Open Shortest Path First
IS-iS
Intermediate System-to-Intermediate System
RIP
Routing Information Protocol
4.3.4.3 IPv4 Dynamic Routing Examples
D*EX
source entry was EIGRP (D)
candidate to be a default route (*)
route is external route (*EX)
4.3.4.4 IPv6 Routing Protocols
RIPng ( RIP next generation)
OSPFv3
EIGRP for IPv6
4.3.4.5 IPv6 Dynamic Routing Protocols