How Hosts Find Their Destination

Mar 4, 2011

I have several Cisco switches connecting our network. Switch N connects to the gateway, Switches Y & Z connect to some hosts. Switch N connects to Y and Y connects to Z. Assume our gateway IP is a Class B address with a netmask of and all the hosts attached on switches Y & Z have static IP addresses assigned to them. This gateway connects to the internet.In addition to this IP address, some of the hosts also have a second IP address assigned to the same NIC. This IP is Class A (10.0.###.###) and have a netmask of A second gateway address is not defined.

The hosts that have 2 IP's bound to their nic, use the 10. address to communicate with each other. (Programs running on the hosts are specifically configured to use 10. address).I have several questions regarding this setup:

1) Assume Host has only 1 IP (Class B) - if the destination is on the same network, does the host system send the packet to the gateway first to find the destination on the network or does the host send a "where are u" packet to the broadcast address to find the destination?

2) Assume Host as 2 IPs (Class A & B) - if the destination is a 10. address, how does the host go about finding it?

Since there is no Gateway defined for the Class A address, does the host simply send out a packet to the broadcast address for the Class A network? or does it go to the gateway defined in the Class B network as it was defined first (i'm assuming primary connection)

3) Assume Switch N's connection to Switch Y is disabled - how will this affect communication between hosts on Switches Y & Z that have a 10. IP trying to share data with each other, using the 10. Address. If the answer is this should not affect it, what additional circumstances are required that may cause the systems with a 10. address to be unable to communicate when the connection from Switch Y to N is terminated?]

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