Description

Some BNG customers in the pool assignment configuration will add the DNS server IPS (family inet xauth-attributes priamry-dns/secondary-dns) to their PPPoE subscribers. If this configuration is missing, subscribers will not get assigned the DNS. Therefore, they cannot resolve the URLs when surfing the internet.

This article provides a commit script to prevent the deletion or omission of this pool configuration.

Symptoms

DNS under the address-assignment pool is deleted from the configuration or omitted during configuration. When a PPPoE connects, this DNS will not be assigned, which causes issues to resolve URLs.

Solution

Missing configuration under ​access address-assignment pool <pool> family inet xauth-attributes <primary-dns/secondary-dns> .

Configure a commit script to prevent this issue.

Login via shell using root password: 

[MASTER]
user@Router-re0> start shell user root    
Password:
root@Router-re0:/var/home/labroot #

Create a file under ​/var/db/scripts/commit: 

root@Router-re0:/var/home/labroot # cd /var/db/scripts/commit
root@Router-re0:/var/db/scripts/commit # vi check-dns.slax

Paste next lines and save the file (wq): 

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";
    
match configuration {
    for-each (access/address-assignment/pool) {
        var $poolname = name; 
        var $pri-dns = family/inet/xauth-attributes/primary-dns;
        var $sec-dns = family/inet/xauth-attributes/secondary-dns;

        /* Declare an error if the Primary DNS is missing */
        if( $poolname && jcs:empty($pri-dns)  ) {
            <xnm:error> {
                 <message> "pool " _ $poolname _ " the Primary DNS is disabled or missing, please check it.";
            } 
        }
        /* Declare an warning if the secondary-dns is missing*/
        else if( $poolname && jcs:empty($sec-dns) ) {
             <xnm:warning> {
                 <message> "pool " _ $poolname _ " the Secondary DNS is disabled or missing, please check it.";
            } 
        }
    }
}

Note: If you have dual RE environment with GRES, create the same file in the backup RE. For this script, if any pool primary-dns is missing, the commit will fail. If the customer just wants to see a pop up warning message, please change '< xnm:error> ' to ' <xnm:warning> '.

Exit from shell and apply the commit script to the configuration: 

set system scripts commit file check-dns.slax
 

Verification

  1. No pool configured: 

    user@Router-re0# show access address-assignment

[Master][edit]
user@Router-re0# commit
re0:
configuration check succeeds
re1:
commit complete
re0:
commit complete

  2. One pool configured and no primary-dns 

    user@Router-re0# show access
address-assignment {
    pool pppoe-1 {
        family inet {
            network 10.167.0.0/16;
        }
    }
}

[Master][edit]
user@Router-re0# commit
re0:
error: pool pppoe-1 the Primary DNS is disabled or missing, please check it.
error: 1 error reported by commit scripts
error: commit script failure

  3. One pool configured and deactivated primary-dns 

    user@Router-re0# show access
address-assignment {
    pool pppoe-1 {
        family inet {
            network 10.167.0.0/16;
            xauth-attributes {
                inactive: primary-dns 10.10.10.10/32;
            }
        }
    }
}

[Master][edit]
user@Router-re0# commit
re0:
error: pool pppoe-1 the Primary DNS is disabled or missing, please check it.
error: 1 error reported by commit scripts
error: commit script failure

  4. One pool and primary-dns configured but not configured secondary-dns, commit pass but pop up warning message 

    user@Router-re0# show access
address-assignment {
    pool pppoe-1 {
        family inet {
            network 10.167.0.0/16;
            xauth-attributes {
                primary-dns 10.10.10.10/32;
            }
        }
    }
}

[MASTER][edit]
user@Router-re0# commit
re0:
warning: pool pppoe-1 the Secondary DNS is disabled or missing, please check it.
re0:
configuration check succeeds
re1:
warning: pool pppoe-1 the Secondary DNS is disabled or missing, please check it.
commit complete
re0:
commit complete

  5. One pool and primary-dns/secondary-dns both configured 

    user@Router-re0# show access
address-assignment {
    pool pppoe-1 {
        family inet {
            network 10.167.0.0/16;
            xauth-attributes {
                primary-dns 10.10.10.10/32;
                secondary-dns 11.11.11.11/32;
            }
        }
    }
}

[MASTER][edit]
user@Router-re0# commit
re0:
configuration check succeeds
re1:
commit complete
re0:
commit complete

  6. Two pools configured but one pool primary-dns is missing 

    user@Router-re0# show access
address-assignment {
    pool pppoe-1 {
        family inet {
            network 10.167.0.0/16;
            xauth-attributes {
                primary-dns 10.10.10.10/32;
                secondary-dns 11.11.11.11/32;
            }
        }
    }
    pool pppoe-2 {
        family inet {
            network 10.177.0.0/16;
        }
    }
}

[MASTER][edit]
user@Router-re0# commit
re0:
error: pool pppoe-2 the Primary DNS is disabled or missing, please check it.
error: 1 error reported by commit scripts
error: commit script failure

  7. Two pools configured but both pools secondary-dns is missing 

    user@Router-re0# show access
address-assignment {
    pool pppoe-1 {
        family inet {
            network 10.167.0.0/16;
            xauth-attributes {
                primary-dns 10.10.10.10/32;
            }
        }
    }
    pool pppoe-2 {
        family inet {
            network 10.177.0.0/16;
            xauth-attributes {
                primary-dns 10.10.10.10/32;
            }
        }
    }
}

[MASTER][edit]
user@Router-re0# commit
re0:
warning: pool pppoe-1 the Secondary DNS is disabled or missing, please check it.
warning: pool pppoe-2 the Secondary DNS is disabled or missing, please check it.
re0:
configuration check succeeds
re1:
warning: pool pppoe-1 the Secondary DNS is disabled or missing, please check it.
warning: pool pppoe-2 the Secondary DNS is disabled or missing, please check it.
commit complete
re0:
commit complete