Intel IXC1100, IXP42X

Intel® IXP42X product line and IXC1100 control plane processors—Ethernet MAC A

Intel® IXP42X Product Line of Network Processors and IXC1100 Control Plane Processor

DM September 2006

424 Order Number: 252480-006US

Broadcast frames can be dropped and prevented from being sent to the NPE. To

accomplish this, the following three conditions must be met:

1. Broadcast Disable bit “b7=1” of the Received Control Register RXCTRL1.

2. Address Mask Registers 1 to 6 are NOT 00 00 00 00 00 00.

3. Address Filter Enable bit “b5=1” of the Received Control Register RXCTRL1.

Multi-cast frame filtering and uni-cast frame filtering can be enabled/disabled by

setting bit 5 of Receive Control Register 1 (RXCTRL1). Setting bit 5 of Receive Control

The NPE can then operate in promiscuous mode and implement a more comprehensive

filtering algorithm if required.

Setting bit 5 of Receive Control Register 1 (RXCTRL1) to logic 1 enables filtering for uni-

cast frames that are received. When uni-cast frames are detected, the destination

address of the received frame must match exactly the value contained in the Uni-Cast

Address Register (UNIADDR). Setting bit 5 of Receive Control Register 1 (RXCTRL1) to

logic 0 allows all uni-cast frames to be passed to the NPE.

For example, if the Uni-Cast Address Register — which is broken into six bytes —

contains the value of 0x00ABCDEF1234 and uni-cast address filtering is enabled: Any

uni-cast frames that are received (determined by bit 47 being set to logic 0) — with

anything other than 0x00ABCDEF1234 — will be discarded.

Multi-cast is when frames are sent to multiple destinations from a single source with a

single-frame transmission. The Address Mask Register (ADDRMASK) and the Address

with common addresses. The address mask is used to tell what each destination

address has in common.

For example, bytes 3 and bytes 4 of every address in this group contain the same

value. The Address Mask Register (ADDRMASK) would contain a hexadecimal value of

0x00FFFF000000. The Address Mask Register will be a logical “AND” with the Address

“AND” values will be compared to see if they match. If they match, the frame will be

passed to the NPE via the remaining logic.

The values seen were as follows:

• Address Mask Register (ADDRMASK) = 00-FF-FF-00-00-00

• Address Register (ADDR) = 00-C1-D2-38-72-00

• Destination Address = A1-C1-D2-47-63-21

Notice that the underlined values are all that matters for the comparison because of the

address mask. The frame in this example would be forwarded to the next phase of the

receive logic. An example of a frame that would be dropped due to address filtering

follows:

• Address Mask Register (ADDRMASK) = 00-FF-FF-00-00-00

• Address Register (ADDR) = 00-C1-D2-38-72-00

• Destination Address = A1-C1-D3-47-63-21

To disable the multi-cast address filtering feature set the Address Mask Register to all

logic 0s.

After the received frame has passed all address filtering checks, the Receive Engine will

capture the length/type field. If the length/type is determined to be a length value field

and the length is less than 64 bytes, the Receive Engine will remove any padded bytes