[Contents] [Prev] [Next] [Index] [Report an Error]

Imposing a Minimum MTU Setting

The maximum transmission unit (MTU) is the greatest amount of data or packet size (in bytes) that can be transferred in one physical frame on a network.

This example tests the MTU of SONET/SDH interfaces, reports when the MTU is less than the value of the $min-mtu variable, here set to 2048, and causes the commit operation to fail.

XSLT Syntax



<?xml version="1.0" standalone="yes"?>


<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:junos="http://xml.juniper.net/junos/*/junos"
    xmlns:xnm="http://xml.juniper.net/xnm/1.1/xnm"
    xmlns:jcs="http://xml.juniper.net/junos/commit-scripts/1.0">


    <xsl:import href="../import/junos.xsl"/>


    <xsl:param name="min-mtu" select="2048"/>


    <xsl:template match="configuration">
        <xsl:for-each select="interfaces/interface[starts-with(name, 'so-')
                                   and mtu and mtu &lt; $min-mtu]">
            <xnm:error>
                <xsl:call-template name="jcs:edit-path"/>
                <xsl:call-template name="jcs:statement">
                    <xsl:with-param name="dot" select="mtu"/>
                </xsl:call-template>
                <message>
                    <xsl:text>SONET interfaces must have a minimum MTU of </xsl:text>
                    <xsl:value-of select="$min-mtu"/>
                    <xsl:text>.</xsl:text>
                </message>
            </xnm:error>
        </xsl:for-each>
    </xsl:template>
</xsl:stylesheet>

SLAX Syntax



version 1.0;


ns junos = "http://xml.juniper.net/junos/*/junos";
ns xnm = "http://xml.juniper.net/xnm/1.1/xnm";
ns jcs = "http://xml.juniper.net/junos/commit-scripts/1.0";


import "../import/junos.xsl";


param $min-mtu = 2048;


match configuration {
    for-each (interfaces/interface[starts-with(name, 'so-') and mtu and 
                        mtu < $min-mtu]) {
        <xnm:error> {
            call jcs:edit-path();
            call jcs:statement($dot = mtu);
            <message> {
                expr "SONET interfaces must have a minimum MTU of ";
                expr $min-mtu;
                expr ".";
            }
        }
    }
}

Testing ex-so-mtu.xsl

To test the example in this section, perform the following steps:

From Imposing a Minimum MTU Setting, copy the Extensible Stylesheet Language Transformations (XSLT) or SLAX script into a text file, and name the file ex-so-mtu.xsl. Copy the ex-so-mtu.xsl file to the /var/db/scripts/commit directory on your routing platform.

Select the following configuration, and press Ctrl+c to copy it to the clipboard. If you are using the SLAX version of the script, change the filename to filename.slax.



system {
    scripts {
        commit {
            file ex-so-mtu.xsl;
        }
    }
}
interfaces {
    so-1/2/2 {
        mtu 2048;
    }
    so-1/2/3 {
        mtu 576;
    }
}

Merge the configuration into your routing platform configuration by issuing the load merge terminal configuration mode command:[edit] user@host# load merge terminal [Type ^D at a new line to end input] > Paste the contents of the clipboard here<
1. At the prompt, paste the contents of the clipboard using the mouse and the paste icon.
2. Press Enter.
3. Press Ctrl+d

Issue the commit command. When you issue the commit command, the following output appears:



[edit]
user@host# commit

[edit interfaces interface so-1/2/3]
    'mtu 576;'
        SONET interfaces must have a minimum MTU of 2048.
error: 1 error reported by commit scripts
error: commit script failure

[Contents] [Prev] [Next] [Index] [Report an Error]