Riverstone Networks WICT1-12 - Manual (Page 69)

Riverstone Networks RS Switch Router User Guide Release 8.0 5-5
Bridging Configuration Guide Access Ports and Trunk Ports (802.1P and 802.1Q support)
Creating a non-IP/non-IPX VLAN
In this example, SNA, DECnet, and AppleTalk hosts are connected to et.1.1 and et.2.(1-4). You can associate all the
ports containing these hosts to a VLAN called ‘RED’ with the VLAN ID 5.
First, create a VLAN named ‘RED’
Next, assign ports to the ‘RED’ VLAN.
5.4 ACCESS PORTS AND TRUNK PORTS (802.1P
AND 802.1Q SUPPORT)
The ports of an RS can be classified into two types, based on VLAN functionality: access ports and trunk ports. By
default, a port is an access port. An access port can belong to at most one VLAN of the following types: IP, IPX or
bridged protocols. The RS can automatically determine whether a received frame is an IP frame, an IPX frame or
neither. Based on this, it selects a VLAN for the frame. Frames transmitted out of an access port contain no special
information about the VLAN to which they belong. These frames are classified as belonging to a particular VLAN
based on the protocol of the frame and the VLAN configured on the receiving port for that protocol.
For example, if port 1 belongs to VLAN IPX_VLAN for IPX, VLAN IP_VLAN for IP and VLAN OTHER_VLAN for
any other protocol, then an IP frame received by port 1 is classified as belonging to VLAN IP_VLAN.
You can use the
port enable 8021p
command to tag frames transmitted from access ports with a one-byte, 802.1p
class of service (CoS) value. The CoS value indicates the frame’s priority. There are 8 CoS values, 0 is the lowest
priority and 7 is the highest.
Trunk ports (802.1Q) are usually used to connect one VLAN-aware switch to another. They carry traffic belonging to
several VLANs. For example, suppose that RS A and B are both configured with VLANs V1 and V2.
Then a frame arriving at a port on RS A must be sent to RS B, if the frame belongs to VLAN V1 or to VLAN V2. Thus
the ports on RS A and B which connect the two RS’s together must belong to both VLAN V1 and VLAN V2. Also,
when these ports receive a frame, they must be able to determine whether the frame belongs to V1 or to V2. This is
accomplished by “tagging” the frames, i.e., by prepending information to the frame in order to identify the VLAN to
which the frame belongs. In the RS switching routers, trunk ports normally transmit and receive tagged frames only.
(The format of the tag is specified by the IEEE 802.1Q standard.) If you configure Spanning Tree Protocol, frames are
transmitted as untagged frames.
Explicit and Implicit VLANs
As mentioned earlier, VLANs can either be created explicitly by the administrator (explicit VLANs) or are created
implicitly by the RS when L3 interfaces are created (implicit VLANs).
rs(config)# vlan create RED sna dec appletalk id 5
rs(config)# vlan add ports et.1.1, et.2.(1-4) to RED