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[MX-Series] Where subscriber-management is enabled and multicast routing is not configured, inet.1 tables are created for inet/inet6 address families

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Article ID: KB32127 KB Last Updated: 01 Sep 2017Version: 1.0
Summary:

If subscribers are present in the particular routing-instance, despite the fact that multicast protocols are not configured on the box, inet.1 tables are created for inet/inet6 address families for that routing instance.

user@router show route table test.?                  
Possible completions:
  <table>              Name of routing table
  test.inet.0
  test.inet.1
  test.inet6.0
  test.inet6.1

The described behavior is applicable for Junos OS releases 15.1 and later.

Symptoms:

On the box with the following configuration:

user@router> show configuration system services 
subscriber-management {
    enable {
        force;
    }
}

user@router> show configuration interfaces ge-2/0/0  
interface-transmit-statistics;
flexible-vlan-tagging;
mtu 4488;
unit 100 {
    encapsulation ppp-over-ether;
    vlan-id 100;
    pppoe-underlying-options {
        dynamic-profile pppoe-dp;
    }
}

Where multicast protocols are not enabled:

user@router> show configuration protocols | match "pim|igmp" 
user@router> 

If subscribers are present in particular routing-instance, inet.1 tables are created for inet/inet6 address families for that routing instance. For illustration purposes, routing-instance 'test' is created as follows:

user@router> show configuration routing-instances test | no-more 
instance-type virtual-router;
system {
    services {
        dhcp-local-server {
            dhcpv6 {
                group ppp {
                    interface pp0.0;
                }
            }
        }
    }
}

If subscribers are present on the device, two additional tables are created with the following addresses:

user@router> show subscribers summary routing-instance test

Subscribers by State
   Active: 24
   Total: 24

Subscribers by Client Type
   PPPoE: 24
   Total: 24

Subscribers by LS:RI
   default:test: 24
   Total: 24

user@router> show route table test.inet.1 

test.inet.1: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

224.0.0.0/24       *[Multicast/180] 00:04:06
                      MultiDiscard

show route table> adsl.inet.0 | no-more

224.0.0.22/32      *[IGMP/0] 00:04:19
                      MultiRecv

user@router> show route table test.inet6.1 | no-more

test.inet6.1: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden) 
+ = Active Route, - = Last Active, * = Both 

ff00::/8 *[Multicast/180] 5d 08:49:57 
MultiResolve 
ff02::/16 *[Multicast/180] 5d 08:49:57 
MultiDiscard 

The tables are not present if there are no active subscribers on the device:

user@router> show subscribers summary routing-instance test

Subscribers by State
   Total: 0

Subscribers by Client Type
   Total: 0

Subscribers by LS:RI
   Total: 0

user@router> show route table test.?                  
Possible completions:
               Name of routing table
  test.inet.0          
  test.inet6.0         

user@router>
Cause:

From the output of routing-options traceoptions, we can see that these tables are triggered when some logical interface is created:

Aug 22 13:11:15.426303 KRT Ifstate: recv len 136 v101 seq 771 ADD ifaddr index 392 devindex 130 flags 0xa0 gen 229 local addr 0.0.0.0 local plen 32 dest addr zero-len dest plen 0
Aug 22 13:11:15.426326 ifa_lock 0.0.0.0 0x59bba00 cnt 0
Aug 22 13:11:15.426362 task_ifachange_single_internal: Starting ifachange of 0x59bba00 for task IF
Aug 22 13:11:15.426381 task_ifachange_single_internal: Finished ifachange of 0x59bba00 for task IF
Aug 22 13:11:15.426391 task_ifachange_single_internal: Starting ifachange of 0x59bba00 for task INET6
Aug 22 13:11:15.426399 task_ifachange_single_internal: Finished ifachange of 0x59bba00 for task INET6
Aug 22 13:11:15.426406 task_ifachange_single_internal: Starting ifachange of 0x59bba00 for task INET
Aug 22 13:11:15.426416 task_ifachange_single_internal: Finished ifachange of 0x59bba00 for task INET
Aug 22 13:11:15.426425 task_ifachange_single_internal: Starting ifachange of 0x59bba00 for task RT
Aug 22 13:11:15.426435 task_ifachange_single_internal: Finished ifachange of 0x59bba00 for task RT
Aug 22 13:11:15.426444 task_ifachange_single_internal: Starting ifachange of 0x59bba00 for task MLD
Aug 22 13:11:15.426451 task_ifachange_single_internal: Finished ifachange of 0x59bba00 for task MLD
Aug 22 13:11:15.426459 task_ifachange_single_internal: Starting ifachange of 0x59bba00 for task IGMP
Aug 22 13:11:15.426523 rt_table_create: Initializing RIB test:default.INET.1
Aug 22 13:11:15.426541 rt_radix_create: Initializing radix tree for RIB INET.1
Aug 22 13:11:15.426595 rt_table_create: Initializing RIB test:default.INET6.1
Aug 22 13:11:15.426610 rt_radix_create: Initializing radix tree for RIB INET6.1
Aug 22 13:11:15.426669 CHANGE   224.0.0.22/32       nhid 0  IGMP     pref 0/0 metric  
Aug 22 13:11:15.426691 ADD      224.0.0.22/32       nhid 0  IGMP     pref 0/0 metric  
Aug 22 13:11:15.426700 rt_close: 1 route proto IGMP

The interface index 392 corresponds to the pseudo-IFL:

user@router> show interfaces demux0.2147483651  
  Logical interface demux0.2147483651 (Index 392) (SNMP ifIndex 10091)
    Flags: Encapsulation: ENET2
    Demux:
      Underlying interface: ge-2/0/0.32767 (Index 377)
    Input packets : 0
    Output packets: 4
    Protocol inet, MTU: 1500
      Flags: No-Redirects, No-neighbor-learn
      Addresses, Flags: Is-Default Is-Primary
        Local: 0.0.0.0
    Protocol inet6, MTU: 1500
    Max nh cache: 75000, New hold nh limit: 75000, Curr nh cnt: 0,
    Curr new hold cnt: 0, NH drop cnt: 0
      Flags: No-Redirects, No-neighbor-learn
      Addresses
        Local: fe80::a81:f4ff:fee8:c294

That IFL is created as a result of the login of the very first subscriber.

Solution:

The behavior described above is an expected default behavior in case IPv6 forwarding is needed on the box. This behavior can be changed by adding the following configuration:

set protocols igmp interface all disable
set protocols mld interface all disable
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