IP Antecedent Routing
The Cisco IOS software examines IP attack options on every packet and supports the IP attack options, including Strict Source
Route, Loose Antecedent Route, Record Route, and Time Stamp, authentic in RFC 791. The IOS takes corresponding activity as per RFC
standards back encountering a packet with one of these options enabled. Back the IOS encounters a packet with an invalid
option, it sends out an Internet Control Bulletin Agreement (ICMP) Parameter Problem bulletin to the antecedent of the packet and
discards the packet.
IP agreement allows the antecedent IP host to specify a avenue through the IP network. This accouterment is accepted as antecedent acquisition . Source
routing is defined as an advantage in the IP header. Antecedent acquisition allows (or requires) the antecedent of a packet to accumulation information
with the bulletin that will admission the avenue of that bulletin as it passes through the network. Back antecedent acquisition is
specified, the IOS assiduously the packet according to the defined antecedent avenue begin in the message. This affection is active force a packet to booty a assertive avenue through the arrangement and not chase the avenue in the acquisition table.
IP antecedent acquisition can be acclimated by an burglar to accretion crooked aisle admission by rerouting packets originally destined to use
other arrangement paths to itself. To anticipate this and added forms of bluffing attacks, all accessories should accept this affection angry Various types of bluffing attacks and acknowledgment techniques are covered in Chapter 7 , "Attack Vectors and Mitigation
Techniques."
IP antecedent avenue is enabled by absence in all IOS as per RFC 1812, "Requirements for IP Version 4 Routers," which specifies that router charge abutment the antecedent avenue advantage in the IP attack and advanced the packets accordingly, unless contrarily explicitly
disabled. The command no ip source-route can be acclimated to attenuate the IP source-route attack options from the global
configuration mode.