which can help mitigate spoofing attacks.
However, there is an inherent vulnerability to this approach: it is trivial for a remote attacker to adjust the TTL of sent packets so that they appear to originating from a directly-connected peer.
A very simple solution to this, as discussed in RFC 5082, is to invert the direction in which the TTL is counted. The maximum value of the 8-bit TTL field in an IP packet is 255; instead of accepting only packets with a TTL set to 1, we can accept only packets with a TTL of 255 to ensure the originator really is exactly one hop away. This is accomplished on IOS with the TTL security feature, by appending ttl-security hops <count> to the BGP peer statement.