Configuration

See --output and --global for how their behaviour is affected by where or how many times they appear on the command line.

See the Examples below on how to set an option differently for multiple routers.

--help

Print a brief help message and exit.

--man

Prints the manual page and exits.

--version

Print the version of cfgmaker. This should match the version of MRTG for which config files are being created.

--ifref nr|ip|eth|descr|name

Select the interface identification method. Default is nr which identifies the router interfaces by their number. Unfortunately the interface numbering scheme in an SNMP tree can change. Some routers change their numbering when new interfaces are added, others change thier numbering every full moon just for fun.

To work around this sad problem MRTG can identify interfaces by 4 other properties. None of these works for all interfaces, but you should be able to find one which does fine for you. Note that especially ethernet addrsses can be problematic as some routers have the same ethernet address on most of their interface cards.

Select ip to identify the interface by its IP number. Use eth to use the ethernet address for identification. Use descr to use the Interface description. Or use name to use the Interface name.

You can specify multiple properties if you wish, separated by commas. In this case, cfgmaker will use the first item in the list which can provide unique identification. This allows you to specify, for example, to use IP address and to use ifName if this is not defined: --ifref ip,name

If your chosen method does not allow unique interface identification on the device you are querying, cfgmaker will tell you about it.

--ifdesc nr|ip|eth|descr|name|type|alias

Select what to use as the description of the interface. The description appears in the "Title[]" property for the target as well as the text header in the HTML code defined in the target's "PageTop[]". Default is to use nr which is just the interface number which isn't always useful to the viewer of the graphs.

There are 6 other properties which could be used. Use ip if you want to use the interface's IP-address. Use eth if you want to use the interface's ethernet address. If you want a better description, you can use either descr, name or alias. Exactly what each of these do varies between different equipment so you might need to experiment. For instance, for a serial interface on a Cisco router running IOS using name might result in "S0" being the interface description , descr might result in "Serial0" and alias might result in "Link to HQ" (provided that is what is used as the interface's "description" in the router's configuration).

Finally, if you want to describe the interface by it's Btype (i.e "ethernetCSMA", "propPointtoPoint" etc) you can use type.

You can specify multiple properties if you wish, separated by commas. In this case, cfgmaker will use the first item in the list which is available for this interface. This allows you to specify, for example, to use any of the different aliases in order of preference.

--if-filter 'filter-expression'

First of all, this is under some development and is experimental.

Use this if you want to have better control over what interfaces gets included into the configuration. The filter-expression is evaluated as a piece of Perl code and is expected to return a truth value. If true, include the interface and if false, exclude the interface.

For a further discussion on how these filters work, see the section "Details on Filters" below.

--if-template template-file

First of all, this is under some development and is experimental.

Use this if you want to control what the line for each target should look like in the configuration file. The contents of the file template-file will be evaluated as a Perl program which generates the lines using certain variables for input and output.

For a further discussion on how these templates work, see the section "Details on Temaplates" below.

--host-template template-file

First of all, this is under some development and is experimental.

Use this if you want to have some extra targets related to the host itself such as CPU utilization, ping response time to the host, number of busy modems etc. The contents of the file template-file will be evaluated once per host as a Perl program which generates the lines using certain variables for input and output.

For a further discussion on how these templates work, see the section "Details on Templates" below.

--community community-string

Use this to set the community for the routers following on the command line to community-string. Individual routers might overrride this community string by using the syntax community@router.

--enable-ipv6

This option enables IPv6 support. It requires the appropriate perl modules; if they are not found then IPv6 is disabled (see the ipv6 documentation).

cfgmaker will use IPv6 or IPv4 depending on the target. If the target is a numeric address, the protocol depends on the type of address. If the target is a hostname, cfgmaker will try to resolve the name first to an IPv6 address then to an IPv4 address.

IPv6 numeric addresses must be specified between square braces.

For example:

 cfgmaker --enable-ipv6 [2001:760:4::1]:165:::2
    

If the target has both an IPv6 address and an IPv4 address with the same hostname, cfgmaker first queries the target using IPv6 and falls back to IPv4 if it fails. This is useful for targets which don't support SNMP over IPv6.

--use-16bit

This option forces the use of 16bit SNMP request IDs. Some broken SNMP agents do not accept 32bit request IDs. Try to avoid this option as much as possible, complain to your agent vendor instead.

--snmp-options :[port][:[timeout][:[retries][:[backoff][:version]]]]

Use this to set the default SNMP options for all routers following on the command line. Individual values might be omitted as well as trailing colons. Note that routers might override individual (or all) values specified by --snmp-options by using the syntax

router[:[port][:[timeout][:[retries][:[backoff][:version]]]]]

--global "bla: abc"

Use this to add global options to the generated config file. You can call --global several times to add multiple options. The line will appear in the configuration just before the config for the next router appearing on the command line.

 --global "workdir: /home/mrtg"
    

If you want some default Options you might want to put

 --global "options[_]: growright,bits"
    

Specifying --global after the last router on the command line will create a line in the configuration file which will appear after all the routers.

--noreversedns

Do not try to reverse lookup IP numbers ... a must for DNS free environments.

--no-down

Normally cfgmaker will not include interfaces which are marked anything but administratively and operationally UP. With this switch you get them all.

--show-op-down

Include interfaces which are operatively down.

--zero-speed speed

Assign this speed in bits-per-second to all interfaces which return 0 for ifSpeed and ifHighSpeed. Some switches, notably Foundry equipment, return a speed of zero for some interfaces. For example, to have all interfaces reporting zero set to 100Mbps, use --zero-speed=100000000.

--subdirs format

Give each router its own subdirectory for the HTML and graphics (or .rrd) files. The directory name is the given format string with a couple of pattern replacements. The string "HOSTNAME" will be replaced by the hostname of the router (however you specified it on the cfgmaker commandline -- it may be an actual hostname or just an IP address), and "SNMPNAME" will be replaced with the device's idea of its own name (the same name that appears on the right side of the "Title" lines). For instance, a call like:

 cfgmaker --subdirs=HOSTNAME__SNMPNAME public@10.10.0.18
    

would result in the generation of lines looking something like:

 Directory[10.10.0.18_1]: 10.10.0.18__fp2200-bothrip-1.3
    

--output file

Write the output from cfgmaker into the file file. The default is to use "STDOUT". --output is expected to appear only once on the command line. If used multiple times, the file specified by the last --output will be used.

--nointerfaces

Don't generate configuration lines for interfaces.

This makes cfgmaker skip all steps related to interfaces which means it will not do any polling of the router to retrieve interface information which speeds up the execution of cfgmaker and it will neither run any interface templates.

--interfaces

This makes cfgmaker generate configuration lines for interfaces (the default behaviour).

The main usage of this option is to negate an --nointerfaces appearing earlier on the command line.

SNMP V3 Options

--enablesnmpv3 {yes|no}

The --enablesnmpv3 option is an optional flag to check for the presence of the Net::SNMP libraries. Cfgmaker will try to determine whether this flag is required and will set the values automatically.

SNMPv3 Arguments

A SNMP context is a collection of management information accessible by a SNMP entity. An item of management information may exist in more than one context and a SNMP entity potentially has access to many contexts. The combination of a contextEngineID and a contextName unambiguously identifies a context within an administrative domain. In a SNMPv3 message, the contextEngineID and contextName are included as part of the scopedPDU. All methods that generate a SNMP message optionally take a --contextengineid and --contextname argument to configure these fields.

Context Engine ID

The --contextengineid argument expects a hexadecimal string representing the desired contextEngineID. The string must be 10 to 64 characters (5 to 32 octets) long and can be prefixed with an optional "0x". Once the --contextengineid is specified it stays with the object until it is changed again or reset to default by passing in the undefined value. By default, the contextEngineID is set to match the authoritativeEngineID of the authoritative SNMP engine.

Context Name

The contextName is passed as a string which must be 0 to 32 octets in length using the --contextname argument. The contextName stays with the object until it is changed. The contextName defaults to an empty string which represents the "default" context.

User-based Security Model Arguments

The User-based Security Model (USM) used by SNMPv3 requires that a securityName be specified using the --username argument. The creation of a Net::SNMP object with the version set to SNMPv3 will fail if the --username argument is not present. The --username argument expects a string 1 to 32 octets in length.

Different levels of security are allowed by the User-based Security Model which address authentication and privacy concerns. A SNMPv3 target will derive the security level (securityLevel) based on which of the following arguments are specified.

By default a securityLevel of 'noAuthNoPriv' is assumed. If the --authkey or --authpassword arguments are specified, the securityLevel becomes 'authNoPriv'. The --authpassword argument expects a string which is at least 1 octet in length. Optionally, the --authkey argument can be used so that a plain text password does not have to be specified in a script. The --authkey argument expects a hexadecimal string produced by localizing the password with the authoritativeEngineID for the specific destination device. The "snmpkey" utility included with the Net::SNMP distribution can be used to create the hexadecimal string (see snmpkey).

Two different hash algorithms are defined by SNMPv3 which can be used by the Security Model for authentication. These algorithms are HMAC-MD5-96 "MD5" (RFC 1321) and HMAC-SHA-96 "SHA-1" (NIST FIPS PUB 180-1). The default algorithm used by the module is HMAC-MD5-96. This behavior can be changed by using the --authprotocol argument. This argument expects either the string 'md5' or 'sha' to be passed to modify the hash algorithm.

By specifying the arguments --privkey or --privpassword the securityLevel associated with the object becomes 'authPriv'. According to SNMPv3, privacy requires the use of authentication. Therefore, if either of these two arguments are present and the --authkey or --authpassword arguments are missing, the creation of the object fails. The --privkey and --privpassword arguments expect the same input as the --authkey and --authpassword arguments respectively.

The User-based Security Model described in RFC 3414 defines a single encryption protocol to be used for privacy. This protocol, CBC-DES "DES" (NIST FIPS PUB 46-1), is used by default or if the string 'des' is passed to the --privprotocol argument. By working with the Extended Security Options Consortium http://www.snmp.com/eso/, the module also supports additional protocols which have been defined in draft specifications. The draft http://www.snmp.com/eso/draft-reeder-snmpv3-usm-3desede-00.txt defines the support of CBC-3DES-EDE "Triple-DES" (NIST FIPS 46-3) in the User-based Security Model. This protocol can be selected using the --privprotocol argument with the string '3desede'. The draft http://www.snmp.com/eso/draft-blumenthal-aes-usm-04.txt describes the use of CFB128-AES-128/192/256 "AES" (NIST FIPS PUB 197) in the USM. The three AES encryption protocols, differentiated by their key sizes, can be selected by passing 'aescfb128', 'aescfb192', or 'aescfb256' to the -privprotocol argument.

Details on Filters

When working with filters, remember that Perl has it's own idea of what truth and false is. The empty string "" and the string "0" are false, all other strings are true. This further imples that any integer value of 0 is false as well as any undef value. It also implies that all references are considered true.

As the filter is evaluated as a Perl expression, several useful constructs in Perl are worth mentioning:

Expressions might be grouped by using parentheses "()". Expressions might be combined using boolean operators such as the following:

"and" (equivalent with "&&")

Boolean "and" of the two expressions, is only true if both expressions are true. Example: expression1 and expression2

"or" (equivalent with "||")

Boolean "or" of the two expressions, is true if either or both expressions are true. Example: expression1 or expression2

"not" (equivalent with "!")

Boolean negation of a single expression. Example: not expression . Yet another example: !expression

(For more details on this I recommend a book on Perl)

Predefined Filter Variables

To facilitate, there are a number of predefined values available to use in the filter. Note that these variables are also available when templates interfaces are evaluated (but not host templates).

Caveat: All these variables' names begin with a dollar sign ($), which is a syntactic requirement for scalar variables in Perl. The danger here is that the dollar sign in many shells is an active character (often used for shell variables exactly as in Perl variables) so it is important to ensure that the Perl expression isn't evaluated by the command line shell as shell code before being passed to cfgmaker as command line arguments. In shells like Bourne shell, ksh shell or bash shell, placing the entire expression within single qoutes will avoid such accidental evaluation:

 '--if-filter=($default_iftype && $if_admin)'

$if_type

This is an integer specifying the interface type as per the SNMP standards and as reported by the polled device. A complete list of interface types would be impractical for this document , but there are a number predefined varables below. Normally, cfgmaker puts in the target's PageTop this iftype value within paranthesis after the name of the interface type. (e.g "propPointToPointSerial (22)").

Here's a list of some of the most common interface types by number:

   6 ethernetCsmacd
   7 iso88023Csmacd
   9 iso88025TokenRing
  15 fddi
  19 E1
  20 basicISDN
  21 primaryISDN
  22 propPointToPointSerial
  23 ppp
  24 softwareLoopback
  30 ds3
  32 frame-relay
  33 rs232
  37 atm
  39 sonet
  44 frameRelayService
  46 hssi
  49 aal5
  53 propVirtual
  62 Fast Ethernet (100BaseT)
  63 ISDN & X.25
  69 Full Duplex Fast Ethernet (100BaseFX)
  94 Asymetric Digital Subscriber Loop (ADSL)
 117 Gigabit Ethernet
 134 ATM Sub Interface
    

$default

True if and only if cfgmaker normally should accepted the interface based on the interfaces administrative and operational state (taking the flags --no-down and --show-op-down into account) and it's type (and a few other things).

$default_ifstate

True if and only if cfgmaker would have accepted the interface based on it's operational and administrative states (also taking into account the presence of the flags --no-down and --show-op-down).

$default_iftype

True if and only if cfgmaker would have accepted the interface based on it's type (and a few type specific details in addition).

$if_admin

True if and only if the interface is in an adminstrative up state.

$if_oper

True if and only if the interface is in an operational up state.

A number of variables are also predefined to easily decide if an interface belong to a certain cathegory or not. Below is all those variables listed together with which if_type numbers each variable will be true for. Note that some variables refer to other variables as well.

$if_is_ethernet

True for ethernet interfaces (nr 6, 7, 26, 62, 69 and 117).

$if_is_isdn

True for various ISDN interface types (nr 20, 21, 63, 75, 76 and 77)

$if_is_dialup

True for dial-up interfaces such as PPP as well as ISDN. (nr 23, 81, 82 and 108 in addition to the numbers of $if_is_isdn).

$if_is_atm

True for miscellaneous ATM related interface types (nr 37, 49, 107, 105, 106, 114 and 134).

$if_is_wan

True for WAN interfaces point to point, Frame Relay and High Speed Serial ( 22,32,44,46)

$if_is_lan

True for LAN interfaces (8, 9, 11, 15, 26, 55, 59, 60 and 115 in addition to the numbers of $if_is_ethernet).

$if_is_dsl

True for ADSL, RDSL, HDSL and SDSL (nr 94, 95, 96, 97)

$if_is_loopback

True for software loopback interfaces (nr 24)

$if_is_ciscovlan

True for Cisco VLAN interfaces (interfaces with the word Vlan or VLAN in their ifdescs)

$if_vlan_id

Returns the vlan id associated with a specific port on Cisco Catalyst switches under both Catalyst OS and IOS, and 3Com switches. If it is not a vlan interface, will return undef.

$if_cisco_trunk

Returns the trunking state of a specific port on Cisco Catalyst switches under both Catalyst OS and IOS. Returns "1" if the interface is a trunk, undef otherwise.

$if_MTU

Returns the Maximum Transfer Unit associated with a specific port.

Besides that, you can also use the variables defined for templates below. Further, all the variables available in cfgmaker is at the scripts disposal even if the use of such features is discouraged. More "shortcuts" in the form of variables and functions will be made available in the future instead.

Examples on Filters

The following filter will not affect which interfaces get's included or excluded, it will make cfgmaker behave as normally.

 '--if-filter=$default'

The following filter will make cfgmaker exclude PPP (23) interfaces:

 '--if-filter=$default && $if_type!=23'

The following filter will make cfgmaker behave as usual except that it will consider the operational state of an interface irrelevant but still reject all interfaces which are administratively down.

 '--if-filter=$if_admin && $default_iftype'

Details on Templates

As quite a few of the predefined variables has values which are are supposed to be used in HTML code some of them have an "HTML-escaped" variant, e.g $html_syslocation is the HTML escaped variant of $syslocation. The HTML escaping means that the chars "<", ">" and "&" are replaced by "&lt;", "&gt;" and "&amp;" and that newlines embedded in the string are prepended with "<BR>" and appended with a space character (if a newline is last in the string it is not touched).

Writable Template Variables

These are the variables available to store the configuration lines in. Some of them are initialized prior to the evaluation of the template but such content normally is comments for inclusion in the final configuration file so those variables might be reset to the empty string in the template code to eliminate the comments. The other way around is also possible, the contents of these variables might be extended with further information for various reasons such as debugging etc.

Once the template has been evaluated, the following happens: if the template is a interface template and the actual interface for some reason is rejected and thus needs to be commented out, all the lines in the variable $target_lines are turned into comments by adding a hash mark ("#") at their beginning. Then all the variables $head_lines, $problem_lines , $target_lines and $separator_lines are concatenated together to form the lines to add to the configuration file.

$target_lines

This variable is the placeholder for the configuration lines created by the template. $target_lines is predefined to be empty when the template code is evaluated.

$head_lines

This variable is intended to be the placeholder for the comment line appearing just before the target in the configuration file. It is initialized with that comment line before the evaluation of the template code and if the template doesn't modify $head_lines during evaluation, the comment will look like usual in the config file.

$problem_lines

This variable is intended to be the placholder for the comment lines describing any problems which might have been encountered when trying to add the target into the configuration. For host templates it's normally not used and for those it's predefined as the empty string. For interface templates $problem_lines is predefined with the error description comments which cfgmaker normally would use for rejected interfaces or as the empty string for accepted interfaces.

It is possible to test against $problem_lines to find out if an interface will be included or rejected but this is not recommended. Test against $if_ok instead.

$separator_lines

This variable is the placeholder for the string to use as the separator between the code for individual targets. The contents of this variable is put after each target (so the lines will appear after the end of the last target in the config as well).

Predefined Template Variables

All the variables below are available for interface templates to use. For host templates, only those listed under "Host and System Variables" are available.

For interface templates the variables listed under "Predefined Filter Variables" are also available.

Host and System Variables

$router_name

This is the fully qualified name for the router. It is affected by the following items on the command line: the router name itself and --dns-domain.

$router_connect

This is the reference string for the router being polled. It is on the form community@router possibly followed by some snmp options. It is affected by the following items on the command line: the router name itself, --community, --snmp-options and --dns-domain. (There's no HTML escaped variant available)

$directory_name

This variable should contain the directory name as cfgmaker normally would use as the value for the "Directory[]" directive. The value is determined by the --subdirs command line option. If --subdirs isn't specified $directory_name will be the empty string. (There's no HTML escaped variant available)

$syscontact

This variable is the router's SNMP sysContact value. (HTML escaped variant: $html_syscontact)

$sysname

This variable is the router's SNMP sysName value. (No HTML escaped variant available)

$syslocation

This variable is the router's SNMP sysLocation value. (HTML escaped variant: $html_syslocation)

$sysdescr

This variable is the router's SNMP sysDescr value. It is normally not used by cfgmaker but might be useful in a template. (HTML escaped variant: $html_sysdescr)

Interface Target Related Variables

$target_name

This is what cfgmaker normally would use as the the name of the target. The target name is what is found within the square brackets, "[]", for target directives. (There's no HTML escaped variant available)

$if_ref

This the reference string for the interface. It is expected to be used in the "Target[xyz]" directive to distinguish what interface to use. The value of this variable is affected by the --ifref command line option. It is normally used together with $router_connect . (There's no HTML escaped variant available)

$if_ok

This variable is true if the interface is going to be included into the configuration file, otherwise false. Don't test against other variables such as $problem_lines to find out if an interface will be rejected or not, use this $if_ok instead.

$default_target_lines

This variable contains all the target lines which cfgmaker by default outputs for this interface. It's useful if you want to have the "standard target" but want to add some extra lines to it by using a template.

By default cfgmaker uses the following directives for each target it generates: Target[], SetEnv[], MaxBytes[], Title[], PageTop[] and if there is any directory specified also the Directory[] directive.

To facilitate the creation of templates which generates target configs which are similar to the default one, each of the above mentioned directive lines have a corresponding variable containing the line as cfgmaker would have output it by default.

Note that none of these have a HTML escaped variant, text in them is HTML escaped where needed. Also note that they do not have any newline at the end.

$default_target_directive

This variable contains the default string for the Target[] directive line.

$default_setenv_directive

This variable contains the default string for the SetEnv[] directive line.

$default_directory_directive

This variable contains the default string for the Directory[] directive line which means it is an empty string (with no newline) if there's no directory.

$default_maxbytes_directive

This variable contains the default string for the MaxBytes[] directive line.

$default_title_directive

This variable contains the default string for the Title[] directive line.

$default_pagetop_directive

This variable contains the default string for the PageTop[] directive lines.

Interface Network Configuration Variables

$if_ip

This variable should contain the IP-address of the interface, if any has been assigned to it. (There's no HTML escaped variant available)

$ifindex

This variable is the SNMP ifIndex for the interface which per definition always is an integer. (There's no HTML escaped variant available)

$if_index

Equivalent with $ifindex.

$if_eth

Contains the ethernet address of the interface, if any. (There's no HTML escaped variant available)

$if_speed

This variable is the speed in bytes/second (with prefixes). (There's no HTML escaped variant available)

$if_speed_str

This variable is a cooked speed description which is either in bits or bytes depending on wether or not the bits option is active and also with the proper prefix for the speed (k, M, G etc). (No HTML escaped variant available)

$if_type_desc

This variable is a textual description of the interface type. (HTML escaped variant: $html_if_type_desc)

$if_type_num

This variable the integer value corresponding to the interface type (for a listing for the value for the more common interface types, see the section DETAILS ON FILTERS above). (No HTML escaped variant available)

$if_dns_name

This is the DNS name for the interface. (No HTML escaped variant available)

Interface Name, Description and Alias Variables

It might seem confusing with both Name, Description and Alias in this context and to some extent it is. Name and Description are usually supported on most equipment but how they are used varies, both between manufacturers as well as between different cathegories of equipment from the same manufacturer. The Alias is at least supported by Cisco IOS, and that variable contains whatever is used in the IOS statement called "description" for the interface (not to be confused with the SNMP variables for Description).

For better control from the command line consider $if_title_desc which contents are controlled by the --if-descr command line option.

$if_snmp_descr

This variable should contain the "raw" description of the interface as determined by the SNMP polling of the router. (HTML escaped variant: $html_if_snmp_descr)

$if_snmp_name

The "raw" name for the interface as provided by SNMP polling. (HTML escaped variant: $html_if_snmp_name)

$if_snmp_alias

The "raw" ifAlias for the interface as provided by SNMP polling. (HTML escaped variant: $html_if_snmp_alias)

$if_cisco_descr

The "raw" CiscolocIfDescr for the interface as provided by SNMP polling. (HTML escaped variant: $html_if_cisco_descr)

$if_description

This is the "cooked" description string for the interface, taking into account the SNMP values found for the interface's RDescr, ifAlias and CiscolocIfDescr. (HTML escaped variant: $html_if_description)

$if_title

The full string cfgmaker by default would have used for the Title[] directive in the configuration as well as the content of the topmost H1 tag in the PageTop[]. Is composed by the contents of $desc_prefix, $if_title_desc and $sysname.

As $if_title depends on $if_title_desc, it is possible to indirectly control $if_title by using the command line option --if-descr.

(HTML escaped variant: $html_if_title)

$if_port_name

If the host is a Cisco Catalyst LAN switch, this variable is the name of that port. (No HTML escaped variant available)

$if_pp_port_name

If the host is a Nortel Passport LAN switch, this variable is the name of that port. (No HTML escaped variant available)

$desc_prefix

This variable is a prefix of the description of what the target is to use in the "Title[]" directive and in the H1 section of the "PageTop[]". Default is "Traffic analysis for ". (HTML escaped variant: $html_desc_prefix)

$if_title_desc

This is the description of the interface normally used by cfgmaker as part of the variable $if_title. The latter is used as the full string in the "Title[]" directove and the H1 section in the PageTop[].

$if_title_desc is controlled by the command line option --if-descr which indirectly controls the contents of $if_title

(HTML escaped variant: $html_if_title_desc)

Help Functions for Templates

The following functions exists to facilitate the writing of host and interface templates.

html_escape(string)

html_escape() takes a string as an argument and returns a new string where the following substitutions has been done: the chars "<", ">" and "&" are replaced by "&lt;", "&gt;" and "&amp;" and that newlines embedded in the string are prepended with "<BR>" and appended with a space character (newlines at the end of the string are not touched).

oid_pick($router_connect,$v3opt,"oid1","oid2"...)

This function will try to poll each of the oids specified until it is successful or has run out of oids. It will return the name of the first oid that worked or undef if it is not successful

Example Template Files

Template Example 1: Eliminating Rejected Targets From Appearing

This template file generates exactly the same configuration code per interface as cfgmaker does by default, with the exception that it eliminates all lines (comments as well as config code) for an interface if the interface happens to be rejected.

 if(not $problem_lines)
 {
   $target_lines .= <<ECHO;

 Target[$target_name]: $if_ref:$router_connect
 SetEnv[$target_name]: MRTG_INT_IP="$if_ip" MRTG_INT_DESCR="$if_snmp_descr"
 ECHO

   if ($directory_name) {
       $target_lines .= "Directory[$target_name]: $directory_name\n";
   }

   $target_lines .= <<ECHO;
 MaxBytes[$target_name]: $if_speed
 Title[$target_name]: $html_desc_prefix$html_if_title_desc -- $sysname
 PageTop[$target_name]: <h1>$html_desc_prefix$html_if_title_desc -- $sysname</h1>
                <div id="sysdetails">
                        <table>
                                <tr>
                                        <td>System:</td>
                                        <td>$sysname in $html_syslocation</td>
                                </tr>
                                <tr>
                                        <td>Maintainer:</td>
                                        <td>$html_syscontact</td>
                                </tr>
                                <tr>
                                        <td>Description:</td>
                                        <td>$html_if_description</td>
                                </tr>
                                <tr>
                                        <td>ifType:</td>
                                        <td>$html_if_type_desc ($if_type_num)</td>
                                </tr>
                                <tr>
                                        <td>ifName:</td>
                                        <td>$html_if_snmp_name</td>
                                </tr>
 ECHO

   $target_lines .= <<ECHO if defined $if_port_name;
                                <tr>
                                        <td>Port Name:</td>
                                        <td>$if_port_name</td>
                                </tr>
 ECHO

   $target_lines .= <<ECHO if defined $if_pp_port_name;
                                <tr>
                                        <td>Port Name:</td>
                                        <td>$if_pp_port_name</td>
                                </tr>
 ECHO

   $target_lines .= <<ECHO;
                                <tr>
                                        <td>Max Speed:</td>
                                        <td>$if_speed_str</td>
                                </tr>
 ECHO

   $target_lines .= <<ECHO if $if_ip;
                                <tr>
                                        <td>Ip:</td>
                                        <td>$if_ip ($if_dns_name)</td>
                                </tr>
 ECHO

   $target_lines .= <<ECHO;
                        </table>
                </div>
 ECHO
 } else {
   $head_lines="";
   $problem_lines="";
   $target_lines="";
   $separator_lines="";
 }

Template Example 2: Simplier Version of Example 1

Example 1 was partly intended to demonstrate how to customize the generation of interface targets but also to provide a hint of how the variables are used in the "default" template which one could consider that cfgmaker normally uses.

If you're only intrested in the easiest way of entirely eliminating those reject interfaces, the template below would do the job as well by using $default_target_lines.

 if($if_ok) {
  $target_lines = $default_target_lines;
 } else {
   $head_lines="";
   $problem_lines="";
   $target_lines="";
   $separator_lines="";
 }

Template Example 3: Creating CPU Targets for Hosts

Below is an example of a host template.

 $head_lines .= <<ECHO;
 #---------------------------------------------------------------------
 ECHO

 my $target_name = $router_name . ".cpu";

 $target_lines .= <<ECHO;

 YLegend[$target_name]: Percentage CPU load
 ShortLegend[$target_name]: %
 Legend1[$target_name]: CPU load in %
 Legend2[$target_name]:
 Legend3[$target_name]: Max Observed CPU load
 Legend4[$target_name]:
 LegendI[$target_name]: &nbsp;CPU Load:
 LegendO[$target_name]:
 WithPeak[$target_name]: ywm
 MaxBytes[$target_name]: 100
 Options[$target_name]: growright, gauge, nopercent
 Title[$target_name]: $router_name CPU load
 Target[$target_name]: 1.3.6.1.4.1.9.2.1.58.0&1.3.6.1.4.1.9.2.1.58.0:$router_connect
 PageTop[$target_name]: <h1>$router_name CPU load</h1>
                <div>
                        <table>
                                <tr>
                                        <td>System:</td>
                                        <td>$router_name in $html_syslocation</td>
                                </tr>
                                <tr>
                                        <td>Maintainer:</td>
                                        <td>$html_syscontact</td>
                                </tr>
                                <tr>
                                        <td>Description:</td>
                                        <td>$html_sysdescr</td>
                                </tr>
                                <tr>
                                        <td>Resource:</td>
                                        <td>CPU.</td>
                                </tr>
                        </table>
                </div>
 ECHO