Cisco ASA 5505 - Manual (Page 443)

21-9
Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 21 Routing Overview
Information About IPv6 Support
Dynamic Routing and Failover
Because static routing systems cannot react to network changes, they generally are considered unsuitable
for large, constantly changing networks. Most of the dominant routing algorithms are dynamic routing
algorithms, which adjust to changing network circumstances by analyzing incoming routing update
messages. If the message indicates that a network change has occurred, the routing software recalculates
routes and sends out new routing update messages. These messages permeate the network, stimulating
routers to rerun their algorithms and change their routing tables accordingly.
Dynamic routing algorithms can be supplemented with static routes where appropriate. A router of last
resort (a router to which all unroutable packets are sent), for example, can be designated to act as a
repository for all unroutable packets, ensuring that all messages are at least handled in some way.
Dynamic routes are synchronized on the standby unit when the routing table changes on the active unit,
which means that all additions, deletions, or changes on the active unit are immediately propagated to
the standby unit. If the standby unit becomes active after the primary unit has been active for a period of
time, routes become synchronized as a part of the failover bulk synchronization process, so the routing
table on the active/standby failover pair should appear the same.
For more information about static routes and how to configure them, see the “Configuring Static and
Default Routes” section on page 22-2 .
Information About IPv6 Support
Many, but not all, features on the ASA support IPv6 traffic. This section describes the commands and
features that support IPv6 and includes the following topics:
• Features That Support IPv6, page 21-9
• IPv6-Enabled Commands, page 21-10
• Entering IPv6 Addresses in Commands, page 21-11
Features That Support IPv6
The following features support IPv6:
Note For features that use the Modular Policy Framework, be sure to use the match any command to match
IPv6 traffic; other match commands do not support IPv6.
• The following application inspections support IPv6 traffic:
– FTP
– HTTP
– ICMP
– SIP
– SMTP
– IPsec-pass-thru
• IPS