default gateway

[aejaz.armi]

i have a layer-2 switch in which i m going to specify the three network ip's(172.16.2.0 for pc,172.16.3.0 for ip phone,172.16.4.0 for fire alarm system) that is connected to the layer-3 switch

and my doubts are:

1.what will be the default gateway(if i gave 172.16.2.1 and can it communicate with other network with in that switch).

2.In a layer-2 switch can i use different natwork ip's for the communication.

3.here i want to provide separate vlan for each network(ex:complete 172.16.2.0 network come under vlan2,172.16.3.0 come under vlan3,172.16.4.0 come under vlan4)

4.If u have any other segestion plz explain me in detail...........

Thank You all

[Richard Burts]

aejaz

Here are answers to your questions:

1) The default gateway that you define will depend on what address you configure for the switch in its management interface. The switch will communicate with other networks by going through the layer 3 switch. It may help if we are clear that the layer 2 switch makes forwarding decisions within each VLAN (subnet) based on the MAC address of the destination. The layer 2 switch can not communicate directly with different networks but requires the services of a layer 3 device.

2) In a layer 2 switch you can not use different network IPs to communicate. see the explanation in (1).

3) In a layer 2 switch separate VLANs are fine. The layer 2 switch understands VLAN and will forward traffic within a VLAN. But the layer 2 switch can not forward between VLANs. To forward between VLANs you need a layer 3 device. From the layer 2 switch you would probably need a trunk to connect to the layer 3 device. The layer 3 device will know what subnet is associated with each VLAN but the layer 2 switch does not know about different subnets.

HTH

Rick