44
If ingress filtering is disabled, VLAN bridge will only check the MAC address table to see if the
destination VLAN exists. If VLAN does not exist, then drop the packet, and if both DA and VLAN do not
exist, forwards the packet. If just knows VLAN existed, then floods the packet to all the ports the VLAN
covers.
If we plan to deploy four VLANs in an office and use a switch to partition them, we should check
which ports belong to which VLAN first. Assuming a 24-port switch is applied.
Name
VID
Port Members
Marketing
2
1,2,3,4,5
Service
3
6,7,20,21,22
Sales
4
8,9,10,11,12,13,14,15,16
Administration
1
17,18,19,23,24
Table 3-6
Next, assign an IP address to each VLAN. Usually, we use 10.x.x.x as internal IP block. Because
there are total four VLANs in the network, we must assign 4 IP blocks to each of them.
Name
VID
Network Address
Marketing
2
10.1.2.0/24
Service
3
10.1.3.0/24
Sales
4
10.1.4.0/24
Administration
1
10.1.1.0/24
Table 3-7
Here we apply the subnet mask 255.255.255, and each VLAN is capable of supporting 254 nodes.
