Cisco Cisco Email Security Appliance C190 Guía Del Usuario
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Cisco AsyncOS 8.0.1 for Email User Guide
Chapter 29 System Administration
Changing Network Settings
DNS Alert
Occasionally, an alert may be generated with the message “Failed to bootstrap the DNS cache” when an
appliance is rebooted. The messages means that the system was unable to contact its primary DNS
servers, which can happen at boot time if the DNS subsystem comes online before network connectivity
is established. If this message appears at other times, it could indicate network issues or that the DNS
configuration is not pointing to a valid server.
appliance is rebooted. The messages means that the system was unable to contact its primary DNS
servers, which can happen at boot time if the DNS subsystem comes online before network connectivity
is established. If this message appears at other times, it could indicate network issues or that the DNS
configuration is not pointing to a valid server.
Clearing the DNS Cache
The Clear Cache button from the GUI, or the d
nsflush
command (for more information about the
dnsflush
command, see the Cisco AsyncOS CLI Reference Guide), clears all information in the DNS
cache. You may choose to use this feature when changes have been made to your local DNS system. The
command takes place immediately and may cause a temporary performance degradation while the cache
is repopulated.
command takes place immediately and may cause a temporary performance degradation while the cache
is repopulated.
Configuring DNS Settings via the Graphical User Interface
Procedure
Step 1
Select Network > DNS.
Step 2
Click Edit Settings.
Step 3
Select whether to use the Internet’s root DNS servers or your own internal DNS server or the Internet’s
root DNS servers and specify alternate DNS servers.
root DNS servers and specify alternate DNS servers.
Step 4
If you want to use your own DNS server(s) enter the server ID and click Add Row. Repeat this for each
server. When entering your own DNS servers, specify a priority as well. For more information, see
server. When entering your own DNS servers, specify a priority as well. For more information, see
.
Step 5
If you want to specify alternate DNS servers for certain domains, enter the domain and the alternate DNS
server IP address. Click Add Row to add additional domains.
server IP address. Click Add Row to add additional domains.
Note
You can enter multiple domains for a single DNS server by using commas to separate domain
names. You can also enter multiple DNS servers by using commas to separate IP addresses.
names. You can also enter multiple DNS servers by using commas to separate IP addresses.
Step 6
Choose an interface for DNS traffic.
Step 7
Enter the number of seconds to wait before cancelling a reverse DNS lookup.
Step 8
You can also clear the DNS cache by clicking Clear Cache.
Step 9
Submit and commit your changes.
Configuring TCP/IP Traffic Routes
Some network environments require the use of traffic routes other than the standard default gateway. You
can manage static routes via the GUI through the Routing page on the Network tab, or the CLI, via the
can manage static routes via the GUI through the Routing page on the Network tab, or the CLI, via the
routeconfig
command.