Sorry folks, i m a bit confused in networking protocols so please help a bit
my questions are
1) Why udp is made if ip is present for communication
2) How routers communicate each other ? Through mac or Ip address
3) How router broadcast? Through Ip or udp

Thank you

do not mix UDP wwith IP.

UDP is a transport protocol, IP is a routing protocol, they both serve totally different functions. TCP and UDP go together as transport protocols offering connection and connectionless services, IP sits underneith and routes the traffic.Udp is a protocol of transport layer and ip is the protocol of network layer. Network layer is third level layer and transport layer is fourth level layer in osi reference model. Every upper level do the task given by its lower level. Ip set rules for the address of the source and destination node in the network. Where udp set the rules transferring of datagram from source to destination over network.
All these layers are from OSI model. The Open Systems Interconnection model (OSI model) is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar communication functions are grouped into logical layers. An instance of a layer provides services to its upper layer instances while receiving services from the layer below.

For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of that path. Two instances at one layer are connected by a horizontal connection on that layer

2) routers communicate by synchronizing there MAC tables which has a list of MAC addresses learned during broadcast to keep update of working paths for routing.
3) routers broadcast at their learned IP addresses not at UDP which is not an addressing protocol.

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