ROUTER AND ITS MEMORY
A router is a device that forwards data
packets along networks. A router is connected to at least two
networks, commonly two LANs or WANs or a LAN and its ISP's network. Routers are
located at gateways, the places where two or more networks connect.
Routers are special
computers built to handle inter network traffic. Routers are very important
network infrastructure devices and they serve many users at same time. The end
users ho not communicate with the routers, but the network traffic generated by
the end users communicate through the router.
APPLICATIONS OF ROUTER
- ACCESS
- DISTRIBUTION
- CORE
- SECURITY
ACCESS
Access routers, including 'small office/home
office' (SOHO) models, are located at customer sites such as branch offices
that do not need hierarchical routing of their
own. Typically, they are optimized for low cost. Some SOHO routers are capable
of running alternative free Linux-based firmware’s like Tomato, Openwork or DD-WRT
DISTRIBUTION
Distribution routers
aggregate traffic from multiple access routers, either at the same site, or to
collect the data streams from multiple sites to a major enterprise location.
Distribution routers are often responsible for enforcing quality of service across
a wide area
network (WAN), so they may have
considerable memory installed, multiple WAN interface connections, and
substantial on board data processing routines. They may also provide
connectivity to groups of file servers or other external networks.
CORE
In enterprises, a core
router may provide a "collapsed backbone"
interconnecting the distribution tier routers from multiple buildings of a
campus, or large enterprise locations. They tend to be optimized for high
bandwidth, but lack some of the features of Edge Routers
SECURITY
External networks must be
carefully considered as part of the overall security strategy. A router may
include a firewall, VPNhandling, and other security functions, or these
may be handled by separate devices. Many companies produced security-oriented
routers, including Cisco Systems' PIX and ASA5500 series, Juniper's Net screen,
Watch guard’s Firebox, Barracuda's variety of mail-oriented devices, and many
others. Routers also commonly perform network address translation, (which allows multiple devices on a network to
share a single public IP address) and State full Packet Inspection. Experts agree that open source routers
are more secure.
INTERNET CONNECTIVITY
AND INTERNAL USE
Routers intended for ISP and major enterprise connectivity usually
exchange routing information using the Border Gateway Protocol (BGP). RFC
4098 standard defines the
types of BGP routers according to their functions:
· EDGE ROUTER: Also
called a Provider Edge router, is placed at the edge of an ISP network. The
router uses External BGP to EBGP routers in
other ISPs, or a large enterprise Autonomous
System.
· SUBSCRIBER EDGE ROUTER: Also
called a Customer Edge router, is located at the edge of the subscriber's
network, it also uses EBGP to its provider's Autonomous System. It is typically
used in an (enterprise) organization.
·
INTER-PROVIDER BORDER ROUTER: Interconnecting ISPs, is a BGP router that maintains BGP
sessions with other BGP routers in ISP Autonomous Systems.
· CORE ROUTER: A core router resides within an Autonomous System as
a back bone to carry traffic between edge routers.
·
WITHIN AN ISP: In the
ISP's Autonomous System, a router uses internal BGP to communicate with other
ISP edge routers, other intranet core
routers, or the ISP's intranet provider border routers.
· "INTERNET BACKBONE:" The Internet no longer has a clearly identifiable
backbone, unlike its predecessor networks. See default (DFZ).
The major ISPs' system routers make up what could be considered to be the
current Internet backbone core.[16] ISPs
operate all four types of the BGP routers described here. An ISP
"core" router is used to interconnect its edge and border routers.
Core routers may also have specialized functions in networks based
on a combination of BGP and Multi-Protocol
Label Switching protocols.
· PORT FORWARDING: Routers
are also used for port forwarding between
private Internets connected servers.
· VOICE/DATA/FAX/VIDEO PROCESSING ROUTERS: Commonly referred to as access servers or gateways, these devices are used to route and process voice,
data, video and fax traffic on the Internet. Since 2005, most long-distance
phone calls have been processed as IP traffic
(VOIP)
through a voice gateway. Use of access server type routers expanded with the
advent of the Internet, first with dial-up access and another resurgence with
voice phone service.
SYMBOL OF ROUTER
ROUTER CONNECTIONS
CONNECTION BY USING CONSOLE PORT
CONNECTION BY USING
AUXILIARY PORT (AUX PORT)
By using a remote
computer through a modem that calls another modem connected to the router with
a cable using the Auxiliary Port on the router. Auxiliary Port (AUX Port)
allows a direct, non-network connection to the router, from a remote location.
The Auxiliary Port (AUX Port) uses a connector type to which modems can plug
into, which allows an administrator from a remote location to access the router
like a console port.
CONNECTION BY USING PROTOCOLS LIKE TELNET, SSH, HTTP OR HTTPS
The routers can be
managed over the network by using standard TCP/IP protocols like Telnet, SSH,
HTTP or HTTPS. Telnet was developed in the early days of the UNIX operating
system to manage computers remotely. A Telnet client and server application
ships with Cisco's IOS software and most computer operating systems. SSH is a
more secure way to configure routers, since the SSH communication is encrypted.
Cisco IOS also has a HTTP server to managed web based communication with the
router.
CONSOLE AND AUXILIARY PORT
Table of Routers with Console and AUX Ports
The table in this section lists the Cisco router series and the
corresponding console and AUX ports.
|
Console Port
|
Console Port Cable
|
AUX Port
|
AUX Port Cable
|
|
|
600
|
RJ-45(management
port)
|
N/A
|
N/A
|
|
|
700
|
N/A
|
N/A
|
||
|
800
|
N/A
|
N/A
|
||
|
1000
|
N/A
|
N/A
|
||
|
1600
|
N/A
|
N/A
|
||
|
1700
|
||||
|
2500
|
||||
|
2600
|
||||
|
3600
|
||||
|
MC3810
|
||||
|
4000
|
||||
|
AS5200/5300
|
||||
|
AS5400
|
||||
|
AS5800
|
||||
|
7100/7200/7300
|
||||
|
7200
|
||||
|
7500
|
||||
|
12000
|
CONSOLE PORT SIGNALS
Note: The console port does not support modem
control or hardware flow control.
AUXILIARY PORT SIGNALS
Note: The auxiliary port supports hardware flow
control and modem control.
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