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Cisco ASA Series CLI Configuration Guide
Chapter 1 Configuring a Cluster of ASAs
Information About ASA Clustering
Multicast Routing in Individual Interface Mode
In Individual interface mode, units do not act independently with multicast. All data and routing packets
are processed and forwarded by the master unit, thus avoiding packet replication.
NAT
NAT can impact the overall throughput of the cluster. Inbound and outbound NAT packets can be sent to
different ASAs in the cluster because the load balancing algorithm relies on IP addresses and ports, and
NAT causes inbound and outbound packets to have different IP addresses and/or ports. When a packet
arrives at an ASA that is not the connection owner, it is forwarded over the cluster control link to the
owner, causing large amounts of traffic on the cluster control link.
If you still want to use NAT in clustering, then consider the following guidelines:
•
No Proxy ARP—For Individual interfaces, a proxy ARP reply is never sent for mapped addresses.
This prevents the adjacent router from maintaining a peer relationship with an ASA that may no
longer be in the cluster. The upstream router needs a static route or PBR with Object Tracking for
the mapped addresses that points to the Main cluster IP address. This is not an issue for a Spanned
EtherChannel, because there is only one IP address associated with the cluster interface.
•
No interface PAT on an Individual interface—Interface PAT is not supported for Individual
interfaces.
•
NAT pool address distribution—The master unit evenly pre-distributes addresses across the cluster.
If a member receives a connection and they have no addresses left, the connection is dropped, even
if other members still have addresses available. Make sure to include at least as many NAT addresses
as there are units in the cluster to ensure that each unit receives an address. Use the
show nat pool
cluster
command to see the address allocations.
•
No round-robin—Round-robin for a PAT pool is not supported with clustering.
•
Dynamic NAT xlates managed by the master unit—The master unit maintains and replicates the
xlate table to slave units. When a slave unit receives a connection that requires dynamic NAT, and
the xlate is not in the table, it requests the xlate from the master unit. The slave unit owns the
connection.
•
Per-session PAT feature—Although not exclusive to clustering, the per-session PAT feature
improves the scalability of PAT and, for clustering, allows each slave unit to own PAT connections;
by contrast, multi-session PAT connections have to be forwarded to and owned by the master unit.
By default, all TCP traffic and UDP DNS traffic use a per-session PAT xlate. For traffic that requires
multi-session PAT, such as H.323, SIP, or Skinny, you can disable per-session PAT. For more
information about per-session PAT, see the
“Per-Session PAT vs. Multi-Session PAT” section on
in the firewall configuration guide.
•
No static PAT for the following inspections—
–
FTP
–
PPTP
–
RSH
–
SQLNET
–
TFTP
–
XDMCP
–
All Voice-over-IP applications
Summary of Contents for 5505 - ASA Firewall Edition Bundle
Page 28: ...Glossary GL 24 Cisco ASA Series CLI Configuration Guide ...
Page 61: ...P A R T 1 Getting Started with the ASA ...
Page 62: ......
Page 219: ...P A R T 2 Configuring High Availability and Scalability ...
Page 220: ......
Page 403: ...P A R T 2 Configuring Interfaces ...
Page 404: ......
Page 499: ...P A R T 2 Configuring Basic Settings ...
Page 500: ......
Page 533: ...P A R T 2 Configuring Objects and Access Lists ...
Page 534: ......
Page 601: ...P A R T 2 Configuring IP Routing ...
Page 602: ......
Page 745: ...P A R T 2 Configuring Network Address Translation ...
Page 746: ......
Page 845: ...P A R T 2 Configuring AAA Servers and the Local Database ...
Page 846: ......
Page 981: ...P A R T 2 Configuring Access Control ...
Page 982: ......
Page 1061: ...P A R T 2 Configuring Service Policies Using the Modular Policy Framework ...
Page 1062: ......
Page 1093: ...P A R T 2 Configuring Application Inspection ...
Page 1094: ......
Page 1191: ...P A R T 2 Configuring Unified Communications ...
Page 1192: ......
Page 1333: ...P A R T 2 Configuring Connection Settings and QoS ...
Page 1334: ......
Page 1379: ...P A R T 2 Configuring Advanced Network Protection ...
Page 1380: ......
Page 1475: ...P A R T 2 Configuring Modules ...
Page 1476: ......
Page 1549: ...P A R T 2 Configuring VPN ...
Page 1550: ......
Page 1965: ...P A R T 2 Configuring Logging SNMP and Smart Call Home ...
Page 1966: ......
Page 2059: ...P A R T 2 System Administration ...
Page 2060: ......
Page 2098: ...1 8 Cisco ASA Series CLI Configuration Guide Chapter 1 Troubleshooting Viewing the Coredump ...
Page 2099: ...P A R T 2 Reference ...
Page 2100: ......