Data Communications Networking Devices - 4th Ed.pdf

5.2 ROUTERS ____________________________________________________________________ 577Figure 5.22and nodesRedrawing the network in Figure 5.10 in terms of its linkssimplicity of illustration. Figure 5.22 contains the revised network consisting offour nodes and ®ve links.When the routers are powered up they only have knowledge of their localconditions. Thus, each routing table would contain a single entry. For example, thetable of router n would have the following value:From n to Link Hop countn local 0For the router represented by node A, its table would then become:From A to Link Hop countA local 0Thirty seconds after being turned on, node Awill broadcast its distance vectorA= 0) to all its neighbors, which in Figure 5.22 are nodes B and C. Node Breceives on link 1 the distance vector A= 0. Upon receipt of this message, it updatesits routing table as follows, adding one to the hop count associated with the distancevector supplied by node 1:From B to Link Hop countB Local 0A 1 1Node B can now prepare its own distance vector B = 0, A= 1) and transmit thatinformation on its connections links 1, 3 and 5).During the preceding period node C would have received the initial distancevector transmission from node A. Thus, node C would have updated its routingtable as follows:From C to Link Hop countC Local 0A 2 1Once it updates its routing table, node C will then transmit its distance vectorC = 0, A= 1) on links 2, 3 and 4.