full-disclosure - Odd packet?

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From: mklinke at futzin.com (Mike Klinke)
Subject: Odd packet?

On Wednesday 26 May 2004 04:05, Valentino Squilloni - Ouz wrote:
> On Wed, 26 May 2004, Steffen Schumacher wrote:
>
> []
>
> > However, as you said, no ISP, which has to follow rules and
> > regulations in the western world allows spoofing of or even
> > routing of the 127/8 net.
>
> Yes, but 127/8 as the source or the destination ?
>
> Even the OP didn't mentioned this.  I'm proned to believe those
> packets have 127.0.0.1 as the source of the packets.

You're correct. I thought I'd sent this to the list last night but 
didn't watch the to: field carefully enough on my reply.

I don't know the mechanism but I think I know what you were 
seeing.  Here is an ethereal packet capture from the time.  We, too,  
were constantly seeing our ISP controlled perimeter router sending 
these packets to our internal equipment. The source MAC address here 
is the perimeter router (Cisco 1700) and the ISP was pretty much 
stumped over the cause.

Regards,  Mike Klinke

----------

Ethereal Frame 1 (60 on wire, 60 captured) 
Arrival Time: Aug 18, 2003 13:48:32.919516000 
Time delta from previous packet: 0.000000000 seconds 
Time relative to first packet: 0.000000000 seconds 
Frame Number: 1 
Packet Length: 60 bytes 
Capture Length: 60 bytes 
Ethernet II 
Destination: 00:01:02:ee:21:95 (00:01:02:ee:21:95) 
Source: 00:06:d7:ee:3a:89 (00:06:d7:ee:3a:89) 
Type: IP (0x0800) 
Trailer: 000000000000 
Internet Protocol, Src Addr: 127.0.0.1 (127.0.0.1), 
  Dst Addr: xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx) 
Version: 4 
Header length: 20 bytes 
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00) 
0000 00.. = Differentiated Services Codepoint: Default (0x00) 
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0 
Total Length: 40 
Identification: 0x252b 
Flags: 0x00 
.0.. = Don't fragment: Not set
..0. = More fragments: Not set 
Fragment offset: 0 
Time to live: 121 
Protocol: TCP (0x06) 
Header checksum: 0x44e2 (correct) 
Source: 127.0.0.1 (127.0.0.1) 
Destination: xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx) 
Transmission Control Protocol, 
  Src Port: 80 (80), Dst Port: 1319 (1319), 
  Seq: 0, Ack: 986251265, Len: 0 
Source port: 80 (80) 
Destination port: 1319 (1319) 
Sequence number: 0 
Acknowledgement number: 986251265 
Header length: 20 bytes 
Flags: 0x0014 (RST, ACK) 
0... .... = Congestion Window Reduced (CWR): Not set 
.0.. .... = ECN-Echo: Not set 
..0. .... = Urgent: Not set 
...1 .... = Acknowledgment: Set 
.... 0... = Push: Not set 
.... .1.. = Reset: Set 
.... ..0. = Syn: Not set 
.... ...0 = Fin: Not set 
Window size: 0 
Checksum: 0x97cc (correct)