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Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
OL-20748-01
Chapter 4 Configuring Security Contexts
Managing Security Contexts
Xlates 8526 8966 93400 0 Summary
Hosts 254 254 262144 0 Summary
Conns [rate] 270 535 42200 1704 Summary
Fixups [rate] 270 535 100000(S) 0 Summary
U = Some contexts are unlimited and are not included in the total.
S = System limit: Combined context limits exceed the system limit; the system limit is
shown.
The following is sample output from the
show resource usage system counter all 0
command, which
shows the resource usage for all contexts, but it shows the system limit instead of the combined context
limits:
hostname#
show resource usage system counter all 0
Resource Current Peak Limit Denied Context
Telnet 0 0 100 0 System
SSH 0 0 100 0 System
ASDM 0 0 80 0 System
IPSec 0 0 10 0 System
Syslogs [rate] 0 0 30000 0 System
Conns 0 0 1000000 0 System
Xlates 0 0 262144 0 System
Hosts 0 0 262144 0 System
Conns [rate] 0 0 170000 0 System
Fixups [rate] 0 0 100000 0 System
Mac-addresses 0 0 65535 0 System
Monitoring SYN Attacks in Contexts
The FWSM prevents SYN attacks using TCP Intercept. TCP Intercept uses the SYN cookies algorithm
to prevent TCP SYN-flooding attacks. A SYN-flooding attack consists of a series of SYN packets
usually originating from spoofed IP addresses. The constant flood of SYN packets keeps the server SYN
queue full, which prevents it from servicing connection requests. When the embryonic connection
threshold of a connection is crossed, the FWSM acts as a proxy for the server and generates a SYN-ACK
response to the client SYN request. When the FWSM receives an ACK back from the client, it can then
authenticate the client and allow the connection to the server.
You can monitor the rate of attacks for individual contexts using the
show perfmon
command; you can
monitor the amount of resources being used by TCP intercept for individual contexts using the
show
resource usage detail
command; you can monitor the resources being used by TCP intercept for the
entire system using the
show resource usage summary detail
command.
The following is sample output from the
show perfmon
command that shows the rate of TCP intercepts
for a context called admin:
hostname/admin#
show perfmon
Context:admin
PERFMON STATS: Current Average
Xlates 0/s 0/s
Connections 0/s 0/s
TCP Conns 0/s 0/s
UDP Conns 0/s 0/s
URL Access 0/s 0/s
URL Server Req 0/s 0/s
WebSns Req 0/s 0/s
TCP Fixup 0/s 0/s
HTTP Fixup 0/s 0/s
FTP Fixup 0/s 0/s
AAA Authen 0/s 0/s
Содержание 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion
Страница 35: ...P A R T 1 Getting Started and General Information ...
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Страница 297: ...P A R T 2 Configuring the Security Policy ...
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Страница 521: ...P A R T 3 System Administration ...
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Страница 613: ...P A R T 4 Reference ...
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