9.2. Security and Reliability Features
OSPF and IS-IS have a number of features—some of them part of the protocol specifications, some of them extensions of the protocol, and some of them inherent characteristics of the protocol—that increase both the security and the reliability of the protocol.
9.2.1. Inherent Security
IS-IS has one significant security advantage over OSPF, which is that the protocol messages themselves are not carried in IP packets. Because of this, IS-IS cannot be attacked by sending faked protocol messages from an external source. Attacks on IS-IS require physical access to a link or router, or logical access such as Telnet or SNMP to a router running IS-IS.
In cases where OSPF accepts only IP packets addressed to the ...