Thanks for the quick reply Nathan! (Apologies for not replying inline, using hotmail, on phone)
Pinging from CE->PE So, CE would send fragmented packet at (for example) 1550....PE would receive, reassemble, and try to send at the original size, and therefore be dropped? Cheers ________________________________________ From: Nathan Ward <[email protected]> Sent: Friday, 15 April 2016 12:06 PM To: CiscoNSP List Cc: [email protected] Subject: Re: [c-nsp] MTU size, fragmentation and drops > On 15/04/2016, at 14:02, CiscoNSP List <[email protected]> wrote: > > Hi Everyone, > > > Generic question on mtu/fragmentation/drops that Im hoping someone can > explain. > > > Our PE cust Interface "had" MTU set to 9100 > > Cust CE WAN Interface has MTU set to 1500 > > > If we pinged with anything above 1500bytes (No DF-bit set), packets were > dropped. > > > If we set our PE's Int to 1500, and pinged above 1500bytes, packets would > pass (But obviously be fragmented). > > > My question is why? i.e. Why would reducing our PE's Ints MTU size to 1500 > "allow" packets above 1500bytes to pass fragmented, but at 9100, they were > dropped? Hi “CiscoNSP List”, What were you pinging from/to? CE pinging the PE? If so, the reply from the PE would have been larger than 1500B - remember the reply would contain the original payload from the request, and would not be fragmented. -- Nathan Ward _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
