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want to know exact defination of..........?

what is the exact defination of

1 ip forwarding

2 routing

3 convergance.

and banifits of ISIS over OSPF


Re: want to know exact defination of..........?


ip forwarding --> This is also called as Ip routing and is used to enable routing on directly connected interfaces on the switch or routers and is enabled by default.

Routing--> routing is used for traffic forwarding from one network to another and uses routers to accomplish this.

convergance--> covergence means that a condition when the routers have a common vie of the n/w and knwo about the different destinations whihc exists and also the route to them.

Benifts if IS-IS over OSPF is :

IS-IS create separate ajacency table for both L1 and L2 routers, Where OSPF doesnot have such thing.

IS-IS doesnot allow the backbone routes to travel to non-backbone areas so this is a kind os totally stubby area implementaion with in a single IS-IS area while OSPF allows the inter area routes to travel in other areas.

ISIS use a circuit ID to uniquely identify each and every interface in an Area whihc is composed of the system ID + Lan ID. OSPF doesnot create such an identity.

ISIS only have DR's over the broadcast network no BDR's are elected while OSPF uses the concept of both DR and BDR.

In ISIS each and every L1 routers form adjacency with DR and each other also and not only with DR whihc results in faster LSP PDU's update while in OSPF we have DR others forming adjanceny with DR and BDR.


-amit singh

Re: want to know exact defination of..........?

thank you Mr.Amit

thank you for you reply. I have one more thing and that is i am preparing for CCDP ARCH. I am not geting any book for it so if you have some material then please send me on my mail id

and can u give me your mail id??


Re: want to know exact defination of..........?


-- ip forwarding: L3 switching. Accepting a packet, choosing an outbound interface through some local policy (generally just looking up the destination address in a local table to find the next hop information towards that destination), rewriting the L2 header, and transmitting it.

-- routing: From a data plan perspective, the same as ip forwarding. From a control plane perspective, the actions required to build a set of local tables and policies used to forward ip packets. This could include things like routing protocols, OER, PBR, and a number of other things.

-- convergence. This one is varied. It could mean the time required after a topology change for traffic to flow between two points in the network. You could choose the farthest points apart in the network, or some specific set of points. It can also mean the time required after a topology change for a single router to take any actions needed and rebuild its local forwarding tables. It can also mean the amount of time it takes for a dynamic routing protocol to propagate and adjust to the topology change (in terms ot the local routing protocol's tables). So, convergence is a rather changeable term.

IS-IS vs OSPF? Pick up a copy of Optimal Routing Design, and look at the appendixes. There's too much to cover in a NetPro answer.



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