Important Process of Password Recovery – Cisco Router …!!

Today we are discuss important process of password recovery for cisco router. This information is very important every network professional. So, develop your idea……………

The two keys to password recovery are knowing that ROMMON (Remote Monitor;a minimal Cisco IOS that allows router access incase the IOS is damaged or unavailable) enables you to reset the configuration register and that a console user can get into ROMMON mode by pressing the Break Key during the first 60  seconds after power-on.Knowing how to reset the configuration register enables you to boot the router (ignoring NVRAM),allowing the console user to see or change the system passwords.

Here are the basic steps associated with password recovery:

1.Turn the router off and then back on again.

2.Press the Break key within the first 60 seconds.

3. Change the configuration register so that bit 6 is 1 (CONFREG COMMAND).

4. Cause the router to load an IOS.(RELOAD command or just power off and on).

5. Avoid setup mode,which will be automatically prompted.

6. Enter privileged mode.

7. View startup configuration to see unencrypted passwords.(EX:SHOW STARTUP-CONFIG).

8. Use the appropriate commands to reset  any encrypted passwords (EX:ENABLE SECRET).

9. Change the configuration register back to the original value.

10. Save the new configuration to active changes (EX:COPY RUNNING-CONFIG STARTUP-CONFIG).

11. Reboot the router.

Do you know Access List Testing Process …!!

Access List Testing Process:

1) Access lis statements operate in a sequential,logical order.They  evaluate packets from the top down,one statement at a time.Placing more frequent access list statements at the top statements at the top will reduce CPU overhead for the router.
2) If a packet header and an access list statement match,the rest of the statements are skipped,and the packet is either permitted or denied.
3) If a packet header does not match an access l,it is tested against the next statement in the list until the end of the list is reached,at which time the packet is denied by an implicit deny.

 Access List rules/notes:

Access lists do not act on packets originating from the router itself (Telnet to another router).
When an IP packet is discarded,ICMP returns a special packet to notify the sender that the destination is unreachable.
There can be only one accss list per protocol,per direction,per port or interface.
IP access list should be created with the ACCESS-LIST command before being applied to an interface.After the list is created,it may be applied with the IP ACCESS-GROUP[ command.
Announced in Cisco IOS 11.2,the named IP access list feature allows IP standard and extended access list to be identified with an alphanumeric string instead of the current numeric (1 to 199) representations.

 An example to remove an access list from an interface:

1. INTERFACE S0
2. NO ACCEESS-GROUP 105

Idea of Access Lists Using for Cisco Router…!!

ACCESS LISTS

 IP access lists are a sequential list of permit and deny conditions that apply to IP addresses or upper-layer protocols. Access Control Lists are used in routers to identify and control traffic.

 Put standard access lists as near the destination as possible and extended access lists as close to the source as possible.

 Access lists have an implicit deny at the end of them automatically. Because of this, an access list should have at least one permit statement in it; otherwise the access list will block all remaining traffic.

 Access lists applied to interfaces default to outbound if no direction is specified.

 -1 is used with IPX access lists to specify wildcard networks.

 Limiting broadcast traffic is important because a broadcast frame is more likely to cause a collision than a unicast frame.

There are two types of access lists

 Standard access lists; standard IP access lists check source address of packets. The result permits or denies the packet output for the ENTIRE PROTOCOL SUITE based on the only source address. Standard access lists do not specify destination addresses. Standard access list have a number from 1 to 99.IPX Standard access lists are numbered from 800 to 899.

 Extended access lists; extended IP access lists check for both source and destination packet addreses.They can also check for SPECIFIC PROTOCOLS,port numbers,and other parameters,which give administrators more flexibility and control. Extended access lists have a number from 100 to 199.IPX extended access lists  are numbered from 900 to 999.

Types of routing protocols – know RIP and IGRP for CCNA Exam ..!!

Today we are discuss important dynamic routing protocol RIP & IGRP. So, develop your knowledge…..

RIP(Routing Information Protocol):

Distance  Vector

Two versions: RIP1 and RIP2

RIP1 and IGRP include a feature called auto summary that cannot be disabled.Auto summary is a feature of the IOS that helps to reduce the size of routing tables.

RIP2 transmits the mask with each route.This feature allows VLSM by passing the mask along with each route so that the subnet is exactly defined.

RIP2 provides clear text and MD% encryption to authenticate the source of a routing update.

RIPs metric is hop count.The maximum hop count is 15.16 is considered to be an infinite metric.

Entire routing tables are broadcast every 30 seconds for RIP;60 seconds for IPX RIP.

If a router running RIP does not receive an update from another router for 180 seconds,it marks the routes served by the non-updating router as being invalid.

A RIP1 only and a RIP2 only router will not be able to exchange routing information.

There are differences between IPX RIP and IP RIP.

Novell RIP uses timer ticks and hops as metrics.

Novell RIP has a 60 second update timer.

IP RIP has a 30 second update timer.

IP RIP has a 180 second hold-down timer.

IGRP (Interior Gateway Routing Protocol) was produced by Cisco in the mid-1980s

Distance Vector

Increased Scalability (works better in large networks than RIP)

More sophisticated metric provide for more accurate routing).Metrics included:bandwidth,delay,reliability,load,and MTU.By  default,omly bandwidth and delay are used.Bandwidth and delay are not measured values,but are set by the DELAY and BANDWIDTH commands.

Supports multiple paths (maintains up to six unequal cost paths).

Requires an  autonomous system number. It does not have t be registered, but all routers within an autonomous system must use the same number to communicate. An “autonomous system” is a set of routers under a common administration.

Supports Load balancing and load Sharing.

4,294.967,295 (over four billion) is considered to be an infinite metric.

255maximum hop count.

MTU (Maximum Transmission Unit);maximum frame length in actetes of a L3PDU that is acceptable to all links on the path.If an inbound router interface receives a frame that is larger than the outbound router’s interface MTU,the router will fragment the packet into units allowed by the outbound router interface.If the DF (Don’t Fragment)bit is set,and the packet is too large for the destination network,the packet will be dropped.ethernet has a MTU of 1500 bytes.

administrativeDistance is an integer value used to determine a preference between two equal routing metrics learned by different routing protocols.It is only important if multiple routing protocols are in use in a single router.When this is true,both routing protocols  can learn routes to the same subnets.because the metric values are different,there is no way to know which routing protocol’s routes are better.This is also considered the rating of trustworthiness.

Idea of Essentially Three classes of Routing Protocols ..!!

We are discuss most essential three classes of routing protocols. This protocol is very important our network technological platform. So, develop our idea…………..

There are essentially three classes of routing protocols:

1) Distance Vector (hops);uses frequent broadcasts on all interfaces to determine the direction and distance to other links and accumulate distance vector.As this process continues,routers discover the best path to non-directly connected networks.The metric values are cumulative.each distance vector protocol uses a different routing algorithm to determine the best route,which generates a number called the metric value for each path through the network.Typically,the smaller the metric,the better the path.EX:RIP and IGRP.

Benefits of Distance  Vector protocols:

Simple design for smaller networks

2) Link State;recreates the exect topology of the entire network for route computation. .Link State takes bandwidth into account using a cost metric. .Link State protocols only send updates when a change occurs,which makes them more attractive for larger networks. .Link –Statealgorithm maintain a complex database of topology information including LSPs (link-State Packets),a topological database,the SPF (Shortest Path First) algorithm,the resulting SPF tree,and finally,a routing table of paths and ports to each network.Bandwidth and delay are the most heavily weighed parts of the metric when using .Link –State protocols.EX:OSPF and NLSP.

Benefits of Link- State protocols:

Allows the use of a more robust addressing scheme

Allows for a larger scalable network

Reduces convergence time

Allows “supernetting”

3) Balanced Hybrid;combines aspects of Link State and Distance Vector routing protocols.Balanced Hybrid uses distance vectors with more accurate metrics to determine the best path to destination networks.EX:EIGRP.

How to router learns forward a packet ….!!

Dear viewers,

Today we are discuss some important information for router platform. This concept is very important router learns how to forward a packet. I think this information is helpful our professional. So, develop our knowledge and comment………….

There are two ways a router learns how to forward a packet:

1) Static Routes;configured by the administrator manually.The administrator must also update the table manually every time a change to the network takes place.Static routes are commonly used when routing from a network to a stub (a network with a single route)network.The default route (gateway of last resort)is a special type of static route used for situations when a route is not known or is infeasible.Be creful,multiple gateways of last resorts can lead to a routing loop.To add a static route use the ROUTER command,and then the NETWORK command.

2) Dynamic Routes;routes that are automatically learned by the router after an administrator configures a router protocol.As soon as dynamic routing is enabled,the routing tables are automatically updated.dynamic routing sues broadcasts and multicasts to communicate with other routers.Each route entry includes a subnet number,the interface out to that subnet,and the IP address of the next router that should receive the packet.

Goals of routing protocols:

Dynamically learn and fill the routing table with a route to all subnets in a network.

If more than one route exists,place the best route in the routing table.

To notice when routes in the table are no longer valid,and to remove those routes  from the table.The types of router protocols that use HELLO are EIGRP,IS-IS,and OSPF.

If a route is removes from the table and another is available,to add the route to the table.

To add new routes,or replace lost routes,with the best currenetly available route as quickly as possible.

Prevent routing loops.

Routed protocols vs. routing protocols:  

Routed protocols use end nodes to encapsulate layer 3 packets along with addressing information(EX :Appletalk,IP,and IPX).

Routing protocols are used to build,share,and maintain routing tables and are used by routers (EX:OSPF and RIP).There are two basic categories of routing protocols:distance vector and link-state.

Idea of Cisco IOS command-line interface-(Part-6)

Today we are discuss most important features of cisco CLI platform. Every professional is very helpful. So, buildup your idea……………….

ROUTER <PROTOCOL> [keyword];starts the routing process.Once routing is enabled,you must use the NETWORK command to indicate which interfaces will be used.

ROUTER RIP;starts RIP.

ROUTER IGRP <AS NUMBER>;starts IGRP,but you must have an AS (Autonomous System)number.All routers within an AS system must use the same number.

NETWORK <NETWORK –NUMBER>;used after ROUTER command to allow the routing process to determine which interfaces will participate in the sending and receiving of routing updates.EX:NETWORK 172.16.0.0

PORT SECURE(enables port security and limits the number of MAC addresses that can be learned on a single port;prevents hackers from simply plugging in).

ERASE STARTUP-CONFIG or WRITE ERASE;erases NVRAM configuration by writing zeros into NVRAM.

BOOT SYSTEM;global command that allows you to specify the source of the IOS software image to load.Attempts are made to load the IOS from the first command in the configuration to the last.If the first fails,the second boot command is used.

BOOT SYSTEM ROM;IOS from ROM is loaded.

BOOT SYSTEM FLASH;the first file from flash memory is loaded.

BOOT SYSTEM TFTP x.x.x.x <FILENAME>;IOS with a filename is loaded from a TFTP server.

SNMP-SERVER ENABLE TRAPS;enables SNMP sysylog messages to be sent as SNMP traps.

DUPLEX;changes duplex mode for an interface.

BANNER MOTD <DELIMETER>;sets the message. of the day on the router.Use the #sign as a delimiter to start and stop the message.

PROMPT <NEW SETTING> ;changes the prompt character.

CONFIGURE TERMINAL;starts global configuration mode from privileged exec mode and allows you to use global commands.Global commands are commands that effect the entire router.

LOGOUT;logs user out of the router.

TERMINAL HISTORY SIZE X;the default history buffer size is 10,but this command will change the history size to a valuebetween 0 and 256.

HISTORY;displays a history of previous commands.Use the up and down arrow keys to navigate.

HISTORY SIZE;sets the maximum number of commands stored in the history buffer.

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