On Mar 1, 2012, at 3:39 PM, Mark W. Jeanmougin wrote:
> On Thu, Mar 1, 2012 at 11:55, Charles DeVoe <scarecrow...@yahoo.com> wrote:
>> I have installed an X520 card with the latest driver ixgbe 3.8. The
>> operating systems is CentOS 5.7. When doing an ifconfig I see receive
>> packets. I also see packets when I do an ethtool -S p1p2. However, when I
>> do tcpdump -i p1p2 I see no packets. Does anyone know why this may be
>> happening.
>> -
>
> Charles,
>
> I've got some experience with the X520 cards under various flavors of
> Linux. I've always had good luck. Although, they do require a bit more
> care and feeding than a Copper e1000. Can you be a bit more specific
> about what you're seeing?
>
> The other thing I'll throw out there: Do you have vlan tags set on
> these packets? If so, you need to add the "vlan" option to tcpdump.
That should only be necessary if you're capturing with a filter; if the command
is just
tcpdump -i p1p2
then no filter was specified, so "vlan" shouldn't be necessary and will, in
fact, *reduce* the number of packets (as it'll mean capturing only packets with
VLAN tags).
"vlan" is used when its side-effect, of causing other filters to go past the
VLAN tag and look at the actual Ethernet type field, is desired, e.g. if you
have tagged packets, "host foobar" won't work as it won't recognize IPv4 or
IPv6 packets, you'd need either
vlan and host foobar
or
host foobar or vlan and host foobar
where the former will match only VLAN-tagged packets to or from "foobar" and
the latter will match untagged or VLAN-tagged packets to or from "foobar".
(I.e., "vlan" isn't an option, it's a term to use in a filter expression.)-
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