Port forwarding tables¶
Port forwarding tables are used in tree-shaped networks to automatically build the forwarding tables that allow the network nodes to forward packets towards their destinations.
- Consider the tree-shaped network shown in the figure below. Assume that the port-forwarding tables are as shown in the figure.
Which of the following affirmations are true ?
If C sends a packet towards A, R3 will immediately forward it on its North interfaceIf B sends a packet towards C, R3 will immediately forward it on its West interfaceIf A sends a packet towards C, R1 will send it to both its East and South interfaces.If A sends a packet towards B, R1 will send it to both its East and South interfaces.If A sends a packet towards B, R1 will send it only to its East interface.
If A sends a packet towards C, R1 will send it only to its South interface.
If R1 receives from R3 a packet whose destination is A, it sends it on both its West and East interfaces.
- Consider the tree-shaped network shown in the figure below. Assume that A has sent a packet towards B but B has not yet replied.
Upon reception of this packet, the port forwarding table of R3 will be updated as :
Dest. OutPort A N B E Upon reception of this packet, the port forwarding table of R1 will be updated as :
Dest. OutPort A W B S Upon reception of this packet, the port forwarding table of R2 will be updated as :
Dest. OutPort A W B W The port forwarding table of R2 will never be updated with information about destination B.Upon reception of this packet, the port forwarding table of R3 will be updated as :
Dest. OutPort A N B N