Junos OS

Dears,

What is the difference between "routing-instance no-forwarding" and "routing-instance virtual-router"

Thanks

BR,

Sherif Ismail

Hello Sherif,

 Please check KB16081 . Although it mainly talks about EX series, the information with regards to routing-instance types are valid for all JUNOS platforms, to my knowledge.

 HTHs,

 Erdem

Thanks Erdem for your reply

So both do same function but difference that "virtual router" has forwarding table but "non forwarding" has none

So what does this mean ? Does this means that non forwarding do not use h/w routing ?

-------------------Quote----------------

Non Forwarding- Use this routing instance type when a separation of routing table information is required. There is no corresponding forwarding table. All routes are installed into the default forwarding tables. IS-IS instances are strictly non forwarding instance types.

Virtual Router - Similar to a VPN routing and forwarding instance type, but used for non-VPN-related applications. There are no virtual routing and forwarding (VRF) import, VRF export, VRF target, or route distinguisher requirements for this instance type

-------------------Unquote----------------

Thanks

BR,

Sherif Ismail

Hello Sherif,

 For a non-forwarding instance type, there is no "separate" forwarding table created, hence "All routes are installed into the default forwarding tables"  as it says in the KB. In other words, forwarding information for a non-forwarding instance will be stored in the default forwarding tables (e.g. inet.0)

 A separate forwarding table would be created for, say, a L3VPN. If you use virtual-router as the instance-type, a separate forwarding table is still created without the requirement for vrf-import|vrf-export, RT etc.

 Take a look at the following example:

[edit routing-instances]
erdems@dogbert# show 
NOFWD {
    instance-type no-forwarding;
    interface fe-0/0/3.40;
}
VROUTER {
    instance-type virtual-router;
    interface lo0.2;
}
VPN {
    instance-type vrf;
    interface lo0.1;
    route-distinguisher 192.168.10.1:1001;
    vrf-target target:65007:1001;
}
#
erdems@dogbert# show interfaces fe-0/0/3.40
vlan-id 40;
family inet {
    address 172.16.5.5/30;
}

[edit]
erdems@dogbert# show interfaces lo0
unit 0 {
    family inet {
        address 192.168.10.1/32;
    }
    family iso {
        address 49.0001.1921.6801.0001.00;
    }
}
unit 1 {
    family inet {
        address 172.16.1.1/32;
    }
}
unit 2 {
    family inet {
        address 172.16.2.2/32;
    }
}

Now let's see how the forwarding tables look like:

erdems@dogbert# run show route forwarding-table summary | match table 
Routing table: inet <<<<<<<<<< the default routing table for ipv4 prefixes
Routing table: __juniper_private1__.inet
Routing table: __juniper_private2__.inet
Routing table: VROUTER.inet <<<<<<<<<< the virtual-router instance type
Routing table: VPN.inet <<<<<<<<<< this is our vrf.
Routing table: iso
Routing table: VROUTER.iso <<<<<<<<<< the virtual-router instance type
Routing table: VPN.iso <<<<<<<<<<<<< this is our vrf.
Routing table: inet6 <<<<<<<<<< the default routing table for ipv6 prefixes
Routing table: __juniper_private1__.inet6
Routing table: VROUTER.inet6 <<<<<<<<<< the virtual-router instance type
Routing table: VPN.inet6 <<<<<<<<<<<<< this is our vrf.
Routing table: mpls

  As you can see, there isn't a separate forwarding table created for routing-instance named NOFWD. In the output below, you can see that the forwarding information for fe-0/0/3.40 (172.16.5.5/30) is installed in inet.0's forwarding table, as the explanation suggests:

erdems@dogbert# run show route 172.16.5.5/30 

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

172.16.5.4/30      *[Direct/0] 00:01:53
                    > via fe-0/0/3.40
172.16.5.5/32      *[Local/0] 00:01:53
                      Local via fe-0/0/3.40

[edit interfaces lo0]
erdems@dogbert# run show route forwarding-table destination 172.16.5.5/30 
Routing table: inet
Internet:
Destination        Type RtRef Next hop           Type Index NhRef Netif
172.16.5.4/30      intf     0                    rslv   396     1 fe-0/0/3.40

Routing table: __juniper_private1__.inet
Internet:
Destination        Type RtRef Next hop           Type Index NhRef Netif
default            perm     0                    rjct    61     1

Routing table: __juniper_private2__.inet
Internet:
Destination        Type RtRef Next hop           Type Index NhRef Netif
default            perm     0                    rjct   101     1

Routing table: VROUTER.inet
Internet:
Destination        Type RtRef Next hop           Type Index NhRef Netif
default            perm     0                    rjct   462     1

Routing table: VPN.inet
Internet:
Destination        Type RtRef Next hop           Type Index NhRef Netif
default            perm     0                    rjct   435     1

   I hope this clarifies it.

  Thanks,

  Erdem

Many Thanks Erdems

That is a great reply 🙂

Hello All

is there any praticular scneario where no-forwaring instance type can be used or come handy ?

Hello,

Yes - when you need to emulate multiple OSPF processes, for example.

https://www.juniper.net/techpubs/en_US/junos9.6/information-products/topic-collections/feature-guide/route-sharing-simple-nonforwarding-instances-configuring-detailed-solutions.html

HTH

Thanks

Alex

Thanks a lot !!!!

So we can use virtual router for this task.

perfect explanations,

thanks