3Com 4007, Implementation Manual, Page: 300 / 684

300 C
HAPTER
14: V
IRTUAL
LAN
S
(VLAN
S
)
Example 2: VLAN Exception Flooding
If data arrives on a bridge port for a certain protocol and VLANs for that
protocol are defined in the module but not on that bridge port, the
default VLAN defines the flooding domain for that data. This case is
called
VLAN exception flooding. Table 59 lists how the VLAN exception
flooding decision is made (assuming a 12-port configuration).
Rules for
Network-based
(Layer 3) VLANs
Whenever an IP VLAN is defined with Layer 3 information, another VLAN
is defined over the same ports called the
All IP Subnets VLAN. Information
about this VLAN is not available to the network administrator. Also, this
VLAN has no VID associated with it and has no IEEE 802.1Q tagging on
any of the ports. Incoming IP frames are assigned to this VLAN if they
cannot be assigned to any of the network-based IP VLANs.
The following IP protocols are applicable to network-based VLANs:
■
IP (hexadecimal 0800 or 0x0800)
■
ARP (0x0806)
■
RARP is (0x8035)
Table 59 VLAN Exception Flooding
Index VLAN Ports
1 Default 1–12
2 IP 1–8
Data
received
on this
port Is
flooded
on this
VLAN
Because
XNS - port 1 VLAN 1 XNS data on port 1 matches the unspecified protocol of the
default VLAN on port 1.
IP - port 2 VLAN 2 IP data received matches IP VLAN 2 for source ports 1 - 8.
IP - port 12 VLAN 1 IP data on port 12 matches the unspecified protocol of the
default VLAN on port 12.