North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: BGP TTL Security

  • From: Danny McPherson
  • Date: Thu Feb 14 15:24:47 2008

On Feb 14, 2008, at 11:28 AM, Ben Butler wrote:
<=191 and the session stays down.

Which is proper bizarre!

Is it necessary to configure this on both side for the session to
re-establish.  Is this a Cisco bug?

You're missing the fundamentals of what protection this mechanism is meat to provide. A remote attacker can craft a packet such that it yields a TTL of 2, 1 or 0 at the target system.

However, what a remote attacker can't do is craft a
packet that yields a TTL or 255 or 254, for example.
You probably want both values to be 254 if you've
got one intermediate hop between the peers.