On Mon, Jul 01, 2002 at 05:27:11PM -0600, Dax Kelson wrote:
> In the "earlier" 2.4 kernels (those that shipped/errata with RHL 7.1
> ~2.4.6), an ethernet frame destined to ff:00:00:00:00:00 were not
> processed and passed up the stack.
>
> Now, with "current" 2.4 kernels (RHL 7.2 errata, and RHL 7.3
> 2.4.9-2.4.18), the same frame IS processed and passed up the stack.
That IEEE 802 MAC address is NOT a broadcast address.
Broadcast would be one with all bits set: ff:ff:ff:ff:ff:ff
The above mentioned MAC address is a multicast frame, because
bit 0x01 in the first octet is set. (All broadcast-frames are
also multicast.)
> The hardware is identical, the NICs are 3c905C.
>
> Is this an intentional optimization/bug?
>
> Here is an ARP request encapsulated in a "bogus" ethernet frame (look at
> the layer 2 destination). A RHL 7.3 (2.4.18) system will respond (see
> Frame 2 below) to this frame, an older RHL 7.1 (2.4.6) system will not
> respond.
Neither should respond. IPv4 ARP is defined using only broadcast
frames.
> Frame 1 (42 on wire, 42 captured)
> Arrival Time: Jul 1, 2002 17:16:35.565996000
> Time delta from previous packet: 1.009672000 seconds
> Time relative to first packet: 1.009833000 seconds
> Frame Number: 3
> Packet Length: 42 bytes
> Capture Length: 42 bytes
> Ethernet II
> Destination: ff:00:00:00:00:00 (ff:00:00:00:00:00)
> Source: ff:00:00:00:00:00 (ff:00:00:00:00:00)
> Type: ARP (0x0806)
> Address Resolution Protocol (request)
> Hardware type: Ethernet (0x0001)
> Protocol type: IP (0x0800)
> Hardware size: 6
> Protocol size: 4
> Opcode: request (0x0001)
> Sender MAC address: 00:01:03:de:56:a4 (00:01:03:de:56:a4)
> Sender IP address: 10.100.0.8 (10.100.0.8)
> Target MAC address: 00:00:00:00:00:00 (00:00:00:00:00:00)
> Target IP address: 10.100.0.10 (10.100.0.10)
>
> Frame 2 (60 on wire, 60 captured)
> Arrival Time: Jul 1, 2002 17:16:35.566146000
> Time delta from previous packet: 0.000150000 seconds
> Time relative to first packet: 1.009983000 seconds
> Frame Number: 4
> Packet Length: 60 bytes
> Capture Length: 60 bytes
> Ethernet II
> Destination: 00:01:03:de:56:a4 (00:01:03:de:56:a4)
> Source: 00:01:03:de:57:37 (00:01:03:de:57:37)
> Type: ARP (0x0806)
> Trailer: 00000000000000000000000000000000...
> Address Resolution Protocol (reply)
> Hardware type: Ethernet (0x0001)
> Protocol type: IP (0x0800)
> Hardware size: 6
> Protocol size: 4
> Opcode: reply (0x0002)
> Sender MAC address: 00:01:03:de:57:37 (00:01:03:de:57:37)
> Sender IP address: 10.100.0.10 (10.100.0.10)
> Target MAC address: 00:01:03:de:56:a4 (00:01:03:de:56:a4)
> Target IP address: 10.100.0.8 (10.100.0.8)
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This archive was generated by hypermail 2b29 : Sun Jul 07 2002 - 22:00:08 EST