Redirect Processing
Redirect Processing Overview
ICMP redirects are messages sent by a router to an originator of data, indicating that a different hop should be used to reach the destination. A router sends a redirect when a routing table lookup for a received datagram results in transmission of the datagram out the same interface on which it was received.
ip redirect
Name
ip redirect - specifies that redirects received via the specified interfaces will be ignored
Syntax
ip redirect enable
no ip redirect
Mode
Interface Configuration
Parameters
none
Description
Use the ip redirect command to specify that redirects received via the specified interface should be ignore. The negative form of this command, no ip redirect, specifies that the redirects should be accepted.
Default
Redirects are accepted by default. Therefore, if ip redirect is not specified, it is the same as if the user had specified the following:
(config-if)# ip redirect enable
Command History
NGC 2.3 - This command was introduced.
Examples
The following example specifies to ignore redirects on interface fxp1.
(config)# interface fxp1
(config-if)# no ip redirect
(config-if)# exit
(config)#
router redirect
Name
router redirect - configures the Redirect protocol on the router
Syntax
router redirect
no router redirect
Mode
Global Configuration
Parameters
none
Description
Use the router redirect command to configure the Redirect protocol on the router. This also enters the user into Redirect Configuration mode, where tracing options can be specified. The negative form of this command, no router redirect, turns off the Redirect protocol.
Default
If router redirect is not specified, it is the same as if the user had specified the following:
(config)# no router redirect
Command History
NGC 2.3 - This command was introduced.
Examples
The following example specifies to ignore redirects on interface fxp1.
(config)# router redirect
(config-router-redirect)# exit
(config)#
trace file
Name
trace file - specifies the file to receive tracing information, the size of the file, whether to overwrite existing files, and the maximum number of files allowed
Syntax
trace file file_name [no-timestamp || overwrite]?
no trace file file_name [no-timestamp || overwrite]?
Mode
Redirect Router Configuration
Parameters
file_name - specifies the name of the file to receive the tracing information. Note that the file name is not specified in quotes.
no-timestamp - specifies that a timestamp should not be prepended to all trace lines
overwrite - specifies to begin tracing by appending or truncating an existing file
Description
The trace file command is associated with each protocol, so that information pertaining to a single protocol can be written to its own file. For Redirect, the trace file command in Redirect Router Configuration Mode specifies a file for tracing of all Redirect events. The negative form of this command disables this tracing. The specific events that are traced are controlled by the trace flag command.
The no-timestamp option disables the pre-pending of a timestamp to all lines written to the trace file. The default is to prepend a timestamp to all lines written to a trace file.
The overwrite option specifies whether to start tracing by truncating or appending to an existing file.
Note: These options are not cumulative across multiple commands.
Default
Redirect tracing options are not configured by default.
Command History
NGC 2.3 - This command was introduced.
Examples
In the following example, tracing is written to the file "rdirct.log". No timestamp will display at the beginning of the trace lines.
(config)# router redirect enable
(config-router-redirect)# trace file rdirct.log no-timestamp
trace flag
Name
trace flag - specifies redirect tracing options
Syntax
trace flag ( [ route | normal | state | policy | task |
timer | all ] ) | ( [ other | packets ] [receive]? [detail?] )
no trace flag ( [ route | normal | state | policy | task |
timer | all ) | ( [ other | packets ] [receive]? [detail?] )
Mode
Redirect Router Configuration
Parameters
Flags common to all protocols:
[ route | normal | state | policy | task | timer | all ] - These tracing flags are common to all protocols. They cannot be associated with a send, receive, or send-receive action item. Similarly, you cannot specify to show detailed information when tracing these flags. These flags are defined as follows:
route - trace routing table changes for routes installed by this protocol or peernormal - trace normal protocol occurrences. Note: Abnormal protocol occurrences are always traced.state - trace state machine transition in the protocolpolicy - trace the application of protocol and user-specified policy to routes being imported or exportedtask - trace system interface and processing associated with this protocoltimer - trace timer usage by this protocolall - turns on all trace flags
Redirect-specific flags:
[ other | packets ] - These Redirect-specific flags can be associated with the receive and detail action items. These flags are defined as follows:
other - trace all other Redirect messages.packets - trace all Redirect packets
[receive]? - optionally specify whether to limit the tracing to received packets
[detail]? - optionally specify to use a more verbose format when displaying information about the contents of packets instead of one or two lines
Description
Use the trace flag command to specify Redirect tracing flags. Each flag must reside on its own configuration line. For example, you cannot specify to trace both task and policy packets in the same command.
Default
The default is for no flags to be explicitly configured.
Command History
NGC 2.3 - This command was introduced.
Examples
In the following example, flags specify to trace both timer usage and state machine transition. This tracing information will be written to the file rdirct.log.
(config)# router redirect enable
(config-router-redirect)# trace file rdirct.log
(config-router-redirect)# trace flag timer
(config-router-redirect)# trace flag state
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