Reference Guide

To ensure integrity, data origin authentication, detection and rejection of replays, and confidentiality of the packet, RFC
4302 and RFC 4303 propose using two security protocols — authentication header (AH) and encapsulating security
payload (ESP). For OSPFv3, these two IPsec protocols provide interoperable, high-quality cryptographically-based
security.
• HA — IPsec authentication header is used in packet authentication to verify that data is not altered during
transmission and ensures that users are communicating with the intended individual or organization. Insert the
authentication header after the IP header with a value of 51. AH provides integrity and validation of data origin
by authenticating every OSPFv3 packet. For detailed information about the IP AH protocol, refer to RFC 4302 .
• ESP — encapsulating security payload encapsulates data, enabling the protection of data that follows in the
datagram. ESP provides authentication and confidentiality of every packet. The ESP extension header is
designed to provide a combination of security services for both IPv4 and IPv6. Insert the ESP header after the IP
header and before the next layer protocol header in Transport mode. It is possible to insert the ESP header
between the next layer protocol header and encapsulated IP header in Tunnel mode. However, Tunnel mode is
not supported in FTOS. For detailed information about the IP ESP protocol, refer to RFC 4303 .
In OSPFv3 communication, IPsec provides security services between a pair of communicating hosts or security
gateways using either AH or ESP. In an authentication policy on an interface or in an OSPF area, AH and ESP are used
alone; in an encryption policy, AH and ESP may be used together. The difference between the two mechanisms is the
extent of the coverage. ESP only protects IP header fields if they are encapsulated by ESP.
You decide the set of IPsec protocols that are employed for authentication and encryption and the ways in which they
are employed. When you correctly implement and deploy IPsec, it does not adversely affect users or hosts. AH and ESP
are designed to be cryptographic algorithm-independent.
OSPFv3 Authentication Using IPsec: Configuration Notes
OSPFv3 authentication using IPsec is implemented according to the specifications in RFC 4552.
• To use IPsec, configure an authentication (using AH) or encryption (using ESP) security policy on an interface or
in an OSPFv3 area. Each security policy consists of a security policy index (SPI) and the key used to validate
OSPFv3 packets. After IPsec is configured for OSPFv3, IPsec operation is invisible to the user.
– You can only enable one security protocol (AH or ESP) at a time on an interface or for an area. Enable
IPsec AH with the ipv6 ospf authentication command; enable IPsec ESP with the ipv6
ospf encryption
command.
– The security policy configured for an area is inherited by default on all interfaces in the area.
– The security policy configured on an interface overrides any area-level configured security for the area
to which the interface is assigned.
– The configured authentication or encryption policy is applied to all OSPFv3 packets transmitted on the
interface or in the area. The IPsec security associations (SAs) are the same on inbound and outbound
traffic on an OSPFv3 interface.
– There is no maximum AH or ESP header length because the headers have fields with variable lengths.
• Manual key configuration is supported in an authentication or encryption policy (dynamic key configuration
using the internet key exchange [IKE] protocol is not supported).
• In an OSPFv3 authentication policy:
– AH is used to authenticate OSPFv3 headers and certain fields in IPv6 headers and extension headers.
– MD5 and SHA1 authentication types are supported; encrypted and unencrypted keys are supported.
• In an OSPFv3 encryption policy:
– Both encryption and authentication are used.
– IPsec security associations (SAs) are supported only in Transport mode (Tunnel mode is not supported).
– ESP with null encryption is supported for authenticating only OSPFv3 protocol headers.
– ESP with non-null encryption is supported for full confidentiality.
597