Thanks abdullah and prakash, 
plz read my question carefully ur answers are not relevant acco

In computing, promiscuous mode or promisc mode is a 
configuration of a network card that makes the card pass 
all traffic it receives to the central processing unit 
rather than just packets addressed to it — a feature 
normally used for packet sniffing.

Each packet includes the hardware (Media Access Control) 
address. When a network card receives a packet, it checks 
if the address is its own. If not, the card normally drops 
the packet. But in promiscuous mode, the card doesn't drop 
the packet, thus allowing the computer to read all packets.

In computing, promiscuous mode or promisc mode is a 
configuration of a network card that makes the card pass 
all traffic it receives to the central processing unit 
rather than just packets addressed to it — a feature 
normally used for packet sniffing.

Each packet includes the hardware (Media Access Control) 
address. When a network card receives a packet, it checks 
if the address is its own. If not, the card normally drops 
the packet. But in promiscuous mode, the card doesn't drop 
the packet, thus allowing the computer to read all packets.

just write a command "sh ip protocol" if link is down check
the ip address that u have put on serial interface or
ethernet interface or chk the clock rate at the end of dce
!!!!!thats it

just write a command "sh ip protocol" if link is down check
the ip address that u have put on serial interface or
ethernet interface or chk the clock rate at the end of dce

plz check encapsulation whether matching with remote device 
or not...and check the clock rate....

Because DTE basically contained the router serial interface
and DCE contained the isp router end ,and two dte cannot
communicate directly atleast one DCE would be there for
communication,and dce provide clocking for
synchronization,thats why we use back to back serial cable
in industry its one end behave as DTE and its other end
behave as DCE.

Passive hub will not regenerate the signal but active hub 
will regenerate the signal ....... so active hub is better.

active hub need electricity bt passive hub didnt 
active hub copy and regnerate signals but passive only copy 
signals

standard IP access list provides basic packet filtering 
abilities, based on the source IP address of a packet only. 
As a general rule, apply standard IP access lists close to 
the destination network to which you wish to permit or deny 
access.Standard IP access lists fall into the numerical 
range 1-99
Unlike standard IP access lists (which only allow you to 
filter packets based on their source IP address), extended 
IP access lists allow a much more granular level of 
control. Extended IP access lists allow filtering not only 
on source addresses, but also on destination addresses, 
protocols, and even applications, based on their port 
number. For example, you might choose to permit or deny a 
group of hosts from accessing a particular server, limit 
access to a telnet server to only a single host, or 
similar.Extended IP access lists are identified through 
their use of the 100-199 numerical range.

In standard access-list the range area is 0-99 but in case 
of extended access-list the range area is 100-199 and in 
standard access-list we cannot create permission on 
specific protocol like bloking the telnet or ftp......we 
can do that in extended access-list.

In standard access-list  we can filter the packet after
routing.and it will applied on destination router.its depend
only on source ip address.


but in case of extended access list we can filter the packet
before routing,and it will applied on source router,its
depend on source ip,destination ip,port and protocol.

standard access list has range area of 0-99
extended has 100-199.

Standard access list basically used to filter packets by IP
address & is basically close to the destination router.(1-99)

Extended access list is used to filter packets based on
address ,protocol & port no. dedicated for particular
services.(100-199)

Proxy ARP (RFC 1027) is a way to make a machine physically 
located on one network appear to be logically part of a 
different physical network connected to the same 
router/firewall. Typically it allows us to hide a machine 
with a public IP address on a private network behind a 
router, and still have the machine appear to be on the 
public network "in front of" the router. The 
router "proxys" ARP requests and all network traffic to and 
from the hidden machine to make this fiction possible.

Consider a router with two interface cards, one connected 
to a public network PUBNET and one connected to a private 
network PRIVNET. We want to hide a server machine on the 
PRIVNET network but have it accessible from the PUBNET 
network. The IP address of the server machine lies in the 
PUBNET network, even though we are placing the machine on 
the PRIVNET network behind the router.

By enabling proxy ARP on the router, any machine on the 
PUBNET network that issues an ARP "who has" request for the 
server's MAC address will get a proxy ARP reply from the 
router containing the router's MAC address. This tells 
machines on the PUBNET network that they should be sending 
packets destined for the server via the router. The router 
forwards the packets from the machines on the PUBNET 
network to the server on the PRIVNET network.

Similarly, when the server on the PRIVNET network issues 
a "who has" request for any machines on the PUBNET network, 
the router provides its own MAC address via proxy ARP. This 
tells the server to send packets for machines on the PUBNET 
network via the router. The router forwards the packets 
from the server on the PRIVNET network to the machines on 
the PUBNET network.

The proxy ARP provided by the router allows the server on 
the PRIVNETnetwork to appear to be on the PUBNET network. 
It lets the router pass ARP requests and other network 
packets in both directions between the server machine and 
the PUBNET network, making the server machine appear to be 
connected to the PUBNET network even though it is on the 
PRIVNET network hidden behind the router.

at layer 3 (network layer)

Network layer

layer 3 network of osi

Network Layer(3) is belong to icmp

icmp internet control message protocol
it works on network layer

icmp work with internet protocol (ip) at layer 3 of osi 
model and inernet layer of tcp model..

Internet Control Message Protocol (ICMP) pings and 
traceroute on the PIX Firewall are handled differently 
based on the version of PIX and ASA code.

Inbound ICMP through the PIX/ASA is denied by default. 
Outbound ICMP is permitted, but the incoming reply is 
denied by default.

** ASA/PIX does not support ICMP redirects, because it does 
not support asymmetric routing

it is used in finding out the error message like if data 
gram is not reaching to the destination.It is reliable 
protocol as compared to Internet protocol.

ICMP works on 
echo-request n echo-reply

in network communications devices echo-request/reply's open 
open in network security devices echo-request/reply is 
close as inbound traffic is restricted by default.

so by this process of echo-request n echo-reply the PING 
and traceroute works and gives the information that the 
channel is established.

this protocal located in router and used to send a message 
to a source host in a case that nework is unreachable

this protocal located in router and used to send a message 
to a source host in a case that nework is unreachable

Register bits are represened in hexadecimal digits....

Cisco register bits are used to control the booting function
of the devices....like we have 4 different types of booting
options available for the cisco devices...
1. ROMMON mode (0x2100)- is used for the normal trouble
shooting like password recovery....
2. BOOTROM (RXBOOT) (0x2101)- is used for the disaster
recovery like IOS recovery....
3. Normal Mode (0x2102)- is the normal booting sequence used
by any device to function properly.
4. Setup mode (0x2142)- is used when the device is not
having any configuration setting in it(deleted) or the
device is brand-new.

VLSM:- Variable length subnet mask. it is used where we have
more than one network running in one internetwork. it
calculation depends on the networks.

VLSM: Variable Length Subnet Mask. It is created many subnet
from One network. 
Adv: Improve network performance
     Avoid waste ip address

VLSM calculation depends on No of host using in single network 

Mainly it is used in point - point connection 
ex: 10.15.1.3/30

VLSM:- Variable length subnet mask.division of subnetted
network in to the smaller network.

its is used to reduced the size of routing table.

example:-200.10.90.0/27
         200.10.90.32/27
         200.10.90.64/27

thr. vlsm:-200.10.90.0/29
           200.10.90.8/29
           200.10.90.16/29

1.Switch are said to be l2 device only but Router are said 
to be L3 device.
2.Switch is said to be H/W Device.Router are said to be S/W 
device.
3.Switch perform faster than the router because it is a H/W 
Device.

Switch are basically layer2 device and it works on Hardware
technology with map the mac addresses and it works with
switch table.

Router is known as layer3 device and works alos on hardware
technology and map the mac addresses. it basically connects
two different networks or netids to each other.it works with
routing table.

1] Switch is separate collision domain. single broad cast
domain. this breakup collision domain.
   Router breakup broadcast domain.

2] Switch hardware oriented. L2 devices. packet transferred
through mac address
   Router Software oriented. L3 devices. packet transferred
through ip address

3] Switch connected between same network
   Router connected between different network.

1.Switch are said to be l2 device only but Router are said 
to be L3 device.
2.Switch is said to be H/W Device.Router are said to be S/W 
device.
3.Switch perform faster than the router in lan.
4.Switches used in LAN in small org.Router are used in WAN
5.We have l3 switches but it will not have all functions 
like Router.

1] Switch is singe broadcast and mutiple collision 
device.i.e switch breack the collision domain
   Router is mutliple collision and mutiple broadcast 
domain..breakup broadcast domain.

2] Switch hardware oriented. L2 devices. packet transferred
through mac address..working at layer 2 of OSI model
   Router Software oriented. L3 devices. packet transferred
through ip address..working at layer 3 of OSI model.

3] Switch extand the same network
   Router connected between different network.

switch is l2             router is l3
switch segment c.d.      router segment b.d
works on frame (mac)     works on packet (ip)
perform switching        perform routing & switching
works on h/w asics (slow )   works on s/w(slow)

1)switch is considered to be an intellengent device because 
there is rare chance of collsion 
                  1)router is an important device because 
it work in network layer third layer of the open system 
interconnection layer
2)switch works on data link layer of the osi reference 
layer,it works depond on mac address(media access control)
                  2)router is used to communicate two or 
more different network
3)when a switch is connected to the host each time it send 
a broadcast ip address and mac address
                   router is consider to be a software 
device  
4) but swich is considered to be a hardware device because 
it uses a special chip call asic(application specific 
integrated circuit)

HUB: 
*Layer 1 device
*Hub Is a Single Broadcast Domain
*Hub Is a Single Collision Domain
*not help in connecting Interanetwork
Router: 
*Layer 3 device
*Router Is a Separate Broadcast Domain
*help in connecting Interanetwork
*Router Is a Separate Collision Domain

Hub Is a Single Broadcast Domain
*Hub Is a Single Collision Domain
*not help in connecting Interanetwork
Router: 
*Layer 3 device
*Router Is a Separate Broadcast Domain
*help in connecting Interanetwork
*Router Is a Separate Collision Domain

Hub is a Physical Layer Divice used to connect host to an 
network.
Hub is only one collusion domain as well as Brodcast Domain.


Router is a Network Layer Device used to connect different 
Networks.
Router's every port is a saperate collusion as well as 
Brodcast Domain.
Routers have own IOS.

HUB

1) Layer1 devices
2) Non intelligent devices
3) Single collision & Broad cast domain
4) This connected in single network
5) LAN connection oriented
6) Data transfer based on MAC address

ROUTER

1) Layer3 devices
2) Intelligent devices
3) Breakup broadcast domain 
4) This connected between different network
5) WAN connection oriented
6) Data transfer based on IP address

HUB
Hub is a Physical Layer Divice used to connect host to an 
network.

1) Layer1 devices
2) Non intelligent devices
3) Single collision & Broad cast domain
4) This connected in single network
5) LAN connection oriented
6) Data transfer based on MAC address

ROUTER

1) Layer3 devices
2) Intelligent devices
3) Breakup broadcast domain 
4) This connected between different network
5) WAN connection oriented
6) Data transfer based on IP address

**** ISR means "Integrated SONET Router" SONET (Synchronous
Optical Network), (Cisco ISR 3303) this model is a end of
life Product.
1) (Integrated SONET/SDH Router) is a high-density access
platform with full SONET interoperability that enables
service providers to deliver a single integrated solution
with both voice services based on time-division multiplexing
(TDM) and IP services. 
2) It dramatically reduces cost of ownership by enabling
service providers to deliver TDM and data services on a
single platform over SONET/SDH (synchronous optical
network/synchronous digital hierarchy) optical fiber networks.

3) The Cisco ISR 3303 router supports the following WAN
interfaces:
      •Clear-channel T1

      •Serial for T1 (1.536 Mbps) channels

      •SONET UPSR and Automatic Protection Switching (APS)
interfaces.
4) It designed to use static and policy routing for most of
its applications. Release 11.3(4)HA3 makes Cisco IOS IP and
bridging functionality available on the Cisco ISR 3303. 
****Non ISR Router 
Cisco 3200 Series are Rugged ISR Products.

An ISR will include the smarts and connections to support 
telephony (Voice over IP) and a number of other specialist 
components such as Intrusion Prevention. Cisco coined the 
phrase to differentiate their products from other router 
vendors (who now also include many of those features).

Presumably these days, a non-ISR router would just route 
packets between different networks (which is the original 
definition of them)