IS-IS vs Routing Protoocols
IS-IS vs Other IP Routing Protocols: Security Considerations
A unique security advantage of IS-IS compared to other IP routing protocols is that IS-IS packets are directly encapsulated over the data link and are not carried in IP packets or even CLNP packets. Therefore, to maliciously disrupt the IS-IS routing environment, an attacker has to be physically attached to a router in the IS-IS network, a challenging and inconvenient task for most network hackers.
Other IP routing protocols, such as RIP, OSPF, and BGP, are susceptible to attacks from remote IP networks through the Internet because routing protocol packets are ultimately embedded in IP packets, which makes them susceptible to remote access by intrusive applications.