HP-UX IPSec version A.02.00 Administrator's Guide

Product Specifications
Product Restrictions
Appendix A
282
When using certificate-based ISAKMP authentication (RSA signatures), HP-UX
IPSec checks that the identity sent by the other node in the Main Mode (MM)
negotiation matches information in the other node’s certificate. HP-UX IPSec always
sends its local IP address as its ID value and the appropriate IP address type (IPv4
or IPv6) as the ID type as the ISAKMP ID payload in MM exchanges. HP-UX IPSec
accepts the following ID types from nodes it communicates with:
— IPv4 address (ID_IPV4_ADDR)
— Fully Qualified Domain Name (ID_FQDN)
— User-Fully Qualified Domain Name (ID_USER_FQDN)
— X.509 Subject Distinguished Name (DN, ID_DER_ASN1_DN)
IPv4 ICMP Messages
Discarding or requiring IPv4 ICMP messages (Internet Control Message Protocol
messages, IP protocol value 1) to be encrypted or authenticated may cause connectivity
problems. Normal network operation may require IP to exchange ICMP messages
between end-to-end hosts and between an end host and an IP gateway (including router
devices). IP may need to exchange ICMP packets with gateway nodes even though no
user (end-to-end) services are being used to the gateways.
Be careful when configuring the default IPSec policy or IPSec policies that affect entire
subnets, because you may inadvertently cause ICMP messages to be discarded. You may
also inadvertently require ICMP messages being transmitted or received from a
non-IPSec gateway or router to be authenticated or encrypted, which will also cause
ICMP packets to be discarded.
IP uses ICMP messages to transmit error and control information, such as in the
following situations:
• IP may periodically send ICMP Echo messages to gateways to determine if the
gateway is up (“Gateway Probes”). If no response is received, the gateway is marked
“Dead” in the IP routing table.
This feature is controlled by the IP kernel parameter ip_ire_gw_probe. By default,
this feature is enabled on all HP-UX systems. Refer to the ndd (1M) manpage for
information on checking or changing this parameter value.
• IP may use ICMP Echo messages with the “Don’t Fragment” flag and ICMP
Destination Unreachable messages with the “Fragmentation Needed” flag to set the
Path Maximum Transmission Unit (Path MTU).
This feature is controlled by the IP kernel parameter ip_pmtu_strategy. Refer to
the ndd (1M) manpage for information on checking or changing this parameter
value.
• IP may send ICMP Redirect messages to redirect traffic to a different gateway.
The transmission of ICMP Redirect messages is controlled by the IP kernel
parameter ip_send_redirects. By default, this feature is enabled on all HP-UX
systems. Refer to the ndd (1M) manpage for information on checking or changing
this parameter value.
• IP may send ICMP Source Quench messages to request the source system to
decrease its transmission rate.