Routing examples 3

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11. Routing examples 3

More complicated network and the routing tables.

The network is made up of ten nodes which differ in addresses in terms of wide and net. The node 69805000 and 69804000 are connected by a serial link. The node 69A01000 is connected to other networks through node 69A02000 where routing continues.

It is good to remember the basic principle – each node seeks for the next hop according to the destination address, which is always contained in the packet. The node which receives the packet processes the packet in similar fashion. This process continues until the packet arrives at the destination.

Comments on the contents of the routing tables:

  • The nodes 69804010 and 69804020 are contained in common CU. The necessary tables are almost identical – the only difference being in the local tables where node 69804010 needs the item 20 to 00 and node 69804020 needs the item 10 to 00. Both nodes use the common set of tables in (N)ode (e)dit.

  • The node 69803002 contains all net address, which appear in the network in it’s net tables. All these net addresses are pointed to node 69803001, so it is possible to use the default item 80 to 69803001, as was explained in the article Routing 2. The fact is used in the net and global tables of all other nodes.

  • The node 69A01000 has it’s default item in net table as A0 to 69A02000. i.e it’s default route in net table is pointed to 69A02000, which connects our network to other networks. This is the reason the table contain explicit written net addresses which appear in our network even though they are all directed to a common node.

  • At the wide table level, the default route option is not possible. This is why all wide table items which occur in the common net are written here. Similar reason is valid at the local table level as well, but this occur only rarely in our example.