| Author |
Message |
Guest
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 Posted:
Thu Oct 13, 2005 11:21 pm Post subject:
Creating a test packet |
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I've got an ethernet driver I'm modifying that sends out a test packet
when it starts to get around a hardware bug. There is no need to ever
get a reply, it's sent only to kickstart things.
I'm a bit worried that the data format used could be interpreted by
some
equipment as a valid packet, though this would be rare. What I want is
some sort of test packet that is universally ignored. The data as it
is
now would start with an LLC header of "00 00 00". Is this likely to be
misinterpreted, or is there something else I can try?
--
Darin Johnson |
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Guest
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| Posted:
Fri Oct 14, 2005 12:31 am Post subject:
Re: Creating a test packet |
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| Quote: | I'm a bit worried that the data format used could be interpreted by
some
equipment as a valid packet, though this would be rare. What I want is
some sort of test packet that is universally ignored. The data as it
is
now would start with an LLC header of "00 00 00". Is this likely to be
misinterpreted, or is there something else I can try?
|
It's very unlikely to be missinterpreted.
http://www.wildpackets.com/support/compendium/ethernet/frame_formats
http://www.ethermanage.com/ethernet/enet-numbers/ieee-lsap-list.html
http://www.ethermanage.com/ethernet/enet-numbers/cisco-lsap-list.html
http://www.ethermanage.com/ethernet/descript-troubleshoot.html
Mention a NULL LSAP with the address fields set to
zero.
Maybe your zero, zero is just the job. You should get the IEEE
802.2 doc and check yourself though. You used to be
able to buy them on-line and download a pdf.
Here are a few possible workarounds.
Avoid broadcast and m'cast dest MAC.
Could you send a packet with an invalid CRC?
Then everything would ignore it.
What happens if you send it to your own MAC address?
Everything else would ignore it, but it might possibly come back to
you.
Buy a NIC, get its address then destroy it. Use that
address as the destination address.
Send a 'good' frame eg an ICMP echo request or an ARP request.
Just pick a destination MAC, the chances of
ever coming into contact with it are rather small.
Unless:- you sell millions of them in which case send
me my share:)
Look through the OUI list and pick an unlikely vendor, say
one that has not yet been taken over and is not too likely to be.
http://www.iana.org/assignments/ethernet-numbers
How about:
080056 Stanford University
Not likely to be taken over any day soon and not
too likely to go into the mass production of
printers, games consoles or refrigerators.
Of course they might sell it. |
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stephen
Guest
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| Posted:
Fri Oct 14, 2005 2:18 am Post subject:
Re: Creating a test packet |
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<anybody43@hotmail.com> wrote in message
news:1129231888.731622.200940@g44g2000cwa.googlegroups.com...
00 is the "null" LSAP, so 00,00 should be OK - i think this can be used as
an 802.2 type "ping".
| Quote: |
Here are a few possible workarounds.
Avoid broadcast and m'cast dest MAC.
Could you send a packet with an invalid CRC?
Then everything would ignore it.
What happens if you send it to your own MAC address?
Everything else would ignore it, but it might possibly come back to
you.
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it shouldnt - but this is what cisco and various others such as the
Wellfleet / Bay Nortel routers do for a "test" packet.
Also - there is a Ethernet type code 9000 which i think is allocated for
"test" - i have seen this "in the wild" with a sniffer.
| Quote: |
Buy a NIC, get its address then destroy it. Use that
address as the destination address.
Send a 'good' frame eg an ICMP echo request or an ARP request.
Just pick a destination MAC, the chances of
ever coming into contact with it are rather small.
Unless:- you sell millions of them in which case send
me my share:)
Look through the OUI list and pick an unlikely vendor, say
one that has not yet been taken over and is not too likely to be.
http://www.iana.org/assignments/ethernet-numbers
How about:
080056 Stanford University
Not likely to be taken over any day soon and not
too likely to go into the mass production of
printers, games consoles or refrigerators.
Of course they might sell it.
-- |
Regards
stephen_hope@xyzworld.com - replace xyz with ntl |
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News Me
Guest
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| Posted:
Fri Oct 14, 2005 6:06 am Post subject:
Re: Creating a test packet |
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anybody43@hotmail.com wrote:
[snip]
| Quote: | Just pick a destination MAC, the chances of
ever coming into contact with it are rather small.
Unless:- you sell millions of them in which case send
me my share:)
Look through the OUI list and pick an unlikely vendor, say
one that has not yet been taken over and is not too likely to be.
http://www.iana.org/assignments/ethernet-numbers
How about:
080056 Stanford University
Not likely to be taken over any day soon and not
too likely to go into the mass production of
printers, games consoles or refrigerators.
|
Rather than hijacking a globally administered MAC address, use a locally
administered one. The second bit of the most-significant byte of the
MAC is the local/global flag (1 = local, 0 = global). The first bit of
the most-significant byte is the multicast/unicast bit (1 = multicast, 0
= unicast), so the second digit MUST be even if you want to prevent
switches from possibly forwarding your packet. So as long as the second
digit of the OUI is one of {2,6,A,E} you should be OK. E.g.,
02-00-00-00-00-01.
NM
--
convert UPPERCASE NUMBER to a numeral to reply |
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Guest
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| Posted:
Sat Oct 15, 2005 11:24 pm Post subject:
Re: Creating a test packet |
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<snip>
You should get the IEEE
| Quote: | 802.2 doc and check yourself though. You used to be
able to buy them on-line and download a pdf.
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802 group stuff specs are currently free (this is mentioned on charles
spurgeon's website)
http://standards.ieee.org/getieee802/ |
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