Advisory - tunneling of IP at exchange points.

Wed Nov 26 13:20:03 UTC 1997

Thanks Paul, wonderful job.  Side-note (taken from the exploit write-up
http://www.linx.net/tunnel-advisory.txt):

>// Adding "log-input" to the end of each access-list line will log
>// the hardware address of the sender for good measure. IOS 11.1
>// and upwards only (from memory)

We find log-input to very unreliable and often producing wrong
information. It indeed operates differently across the 11.1 train (no
comment on 11.2 offered) I think 11.1.15 breaks it badly. Albeit
improperly worded and not well defined in print on CCO, please reference
cisco BUGid CSCdj40503 prior to trusting log-input for any valid info. 

Best regards,

David Van Allen - FASTNET(tm) / You Tools Corporation
dave at fast.net (888)321-FAST(3278) http://www.fast.net
FASTNET - Business and Personal Internet Solutions

> -----Original Message-----
> From:	Paul Thornton [SMTP:prt at linx.net]
> Sent:	Tuesday, November 25, 1997 9:47 AM
> To:	nanog at merit.edu
> Cc:	eof at ripe.net; se-gix at sunet.se; mae-east-tech at uu.net;
> membership at linx.net; ops at linx.net
> Subject:	Advisory - tunneling of IP at exchange points.
> 
> -- PLEASE NOTE: If you are replying to this, consider pruning the list
> --              of cc's rather than crossposting replies wildly!
> Thanks.
> 
[snip]

> The LINX and several of its members have recently had to take action
> against an ISP that was using GRE tunneling between exchange points
> to appropriate the capacity of other ISPs.
> 
> Keith Mitchell
> 
> Chairman
> London InterNet Exchange       keith at linx.org
> Geneva House, 3 Park Road
> Peterborough  PE1 2UX
> United Kingdom
> Phone: +44 1733 705000         (fax 353929)
> 
> 
> Paul
> 
> --
> Paul Thornton, Network Engineer, London Internet Exchange Ltd.
> Tel: 07000 783797   Mobile: +44 467 372205