Description

This article explains the meaning of ‘Next hop type: Fictitious’ , when it is seen under certain BGP routing tables.

Symptoms

Sometimes, you may see ‘Next hop type: Fictitious’ under certain BGP address-families’ route tables. For example: 

user@mx> show route table bgp.inetsrte.0 extensive | no-more
bgp.inetsrte.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
98-10.0.0.7-6534<sr>/96 (1 entry, 0 announced)
        *BGP    Preference: 170/-101
        SRTE Policy Path:
                   Path preference: 99
                   Binding-SID: 1006534
           Segment list:
                      Weight: 1
                      Label: 100064      ttl: Local-ttl-policy
                      Label: 100054      ttl: Local-ttl-policy
                      Label: 100034      ttl: Local-ttl-policy
                      Label: 100044      ttl: Local-ttl-policy
                      Label: 100074      ttl: Local-ttl-policy
                Next hop type: Fictitious, Next hop index: 0
                Address: 0x7e208dc
                Next-hop reference count: 1
                Next hop: 10.0.0.77
                State: <Active Int Ext>
                Local AS: 19211 Peer AS: 19211
                Age: 14:25:55
Or…

user@mx > show route table inetflow.0 extensive
inetflow.0: 1 destinations, 1 routes (1 active, 0 holddown, 0 hidden)
12.12.12.12,*/term:1 (1 entry, 1 announced)
TSI:
KRT in dfwd;
Action(s): rate-limit 10000kbps,count
Page 0 idx 0, (group Clean-Pipe type Internal) Type 1 val 0x33c6578 (adv_entry)
   Advertised metrics:
     Nexthop: Self
     Localpref: 100
     AS path: [9924] I
     Communities: 9924:4300 traffic-rate:9924:1250000
Path 12.12.12.12,* Vector len 4.  Val: 0
        *Flow   Preference: 5
                Next hop type: Fictitious, Next hop index: 0
                Address: 0x1e11a04
                Next-hop reference count: 1
                State: <Active>
                Local AS:  9924
                Age: 3:40:49
                Validation State: unverified
                Task: RT Flow
                Announcement bits (2): 0-Flow 1-BGP_RT_Background
                AS path: I
                Communities: traffic-rate:9924:1250000

Solution

JUNOS uses fictitious next hop type when it does not intend to perform next-hop resolution, and consider the protocol next-hop is good. This is often seen is the case of BGP FlowSpec routes (table inetflow.0 ), BGP SRTE routes (table bgp.inetsrte.0 ), or BGP Link-State distribution routes (table lsdist.0 ).

  • In FlowSpec scenario, a router receives such routes to perform ‘blackhole’ or ‘rate-limit’ accordingly.

  • In SRTE scenario, a router forwards the traffic according to the assigned segment list (label information).

  • In BGP Link-State scenario, a router forwards traffic based on the NorthStar Controller’s policy through PCEP.

The protocol next-hop of BGP route that is flagged as ‘fictitious’ here is of no use for actual traffic forwarding.

Related Information