On Tue, 2011-05-31 at 14:37 -0500, Gary Gatten wrote: > Hello, > > Anyone know how to force the Cisco IOS, specifically netflow, to use > packet sizes smaller than 1464 bytes? It doesn’t seem to be honoring > the MTU size of the interfaces. It gets fragmented and then Checksum > is invalid, and then ntop doesn’t see the packets. Annoying….
Um, gets fragmented by *what* and where? Fragmentation isn't *supposed* to corrupt datagrams, by what is the checksum being invalid being reported? Also, whence 1464? The maximum UDP payload on a standard 1500 byte MTU Ethernet-like network is 1472 bytes before the IPv4 datagram carrying the UDP datagram carrying the user message has to be fragmented. Does your network have a smaller than 1500 byte MTU? While IP fragmentation is indeed frowned upon, "not honoring the MTU size" is a bit strong - UDP-using applications can indeed send messages large enough to require fragmentation by IP. For example EDNS in DNS will do so, and it isn't considered dishonorable :) rick jones > I’ve googled for hours and haven’t found anything yet. > > TIA > > Gary > > Tags: netflow, ntop, exporter not recognized, cant see netflow traffic > > > > "This email is intended to be reviewed by only the intended recipient > and may contain information that is privileged and/or confidential. If > you are not the intended recipient, you are hereby notified that any > review, use, dissemination, disclosure or copying of this email and > its attachments, if any, is strictly prohibited. If you have received > this email in error, please immediately notify the sender by return > email and delete this email from your system." > _______________________________________________ > Ntop mailing list > [email protected] > http://listgateway.unipi.it/mailman/listinfo/ntop _______________________________________________ Ntop mailing list [email protected] http://listgateway.unipi.it/mailman/listinfo/ntop
