[j-nsp] Why JUNOS need re-establish neighbour relationship when configuring advertise-inactive

[Roger Wiklund]

Hi

What version are you running? Is this on MX?

Just for kicks I tried this setup on my SRX300 in packet mode running
15.1X49-D100, and it works without session reset.
https://www.juniper.net/documentation/en_US/junos/topics/example/bgp-advertise-inactive.html

The only difference is that I only have one single device with with
VRs, then loopback cables between them.

set interfaces ge-0/0/0 unit 0 family inet address 10.0.0.1/30
set interfaces ge-0/0/1 unit 0 family inet address 10.0.0.2/30
set interfaces ge-0/0/2 unit 0 family inet address 20.0.0.1/30
set interfaces ge-0/0/3 unit 0 family inet address 20.0.0.2/30

set policy-options policy-statement export-static term t1 from protocol static
set policy-options policy-statement export-static term t1 then accept
set policy-options policy-statement export-static term t2 then reject

set routing-instances VR1 instance-type virtual-router
set routing-instances VR1 interface ge-0/0/0.0
set routing-instances VR1 routing-options static route 8.8.8.8/32 discard
set routing-instances VR1 routing-options autonomous-system 100
set routing-instances VR1 protocols bgp log-updown
set routing-instances VR1 protocols bgp group TO-VR2 export export-static
set routing-instances VR1 protocols bgp group TO-VR2 neighbor 10.0.0.2
peer-as 200

set routing-instances VR2 instance-type virtual-router
set routing-instances VR2 interface ge-0/0/1.0
set routing-instances VR2 interface ge-0/0/2.0
set routing-instances VR2 routing-options static route 8.8.8.8/32 discard
set routing-instances VR2 routing-options autonomous-system 200
set routing-instances VR2 protocols bgp log-updown
set routing-instances VR2 protocols bgp group TO-VR1 neighbor 10.0.0.1
peer-as 100
set routing-instances VR2 protocols bgp group TO-VR3 advertise-inactive
set routing-instances VR2 protocols bgp group TO-VR3 neighbor 20.0.0.2
peer-as 300

set routing-instances VR3 instance-type virtual-router
set routing-instances VR3 interface ge-0/0/3.0
set routing-instances VR3 routing-options autonomous-system 300
set routing-instances VR3 protocols bgp log-updown
set routing-instances VR3 protocols bgp group TO-VR2 neighbor 20.0.0.1
peer-as 200

Before advertise-inactive:

Groups: 4 Peers: 4 Down peers: 0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last
Up/Dwn State|#Active/Received/Accepted/Damped...
10.0.0.1                100         33         32       0       0
 11:52 Establ
  VR2.inet.0: 0/1/1/0
10.0.0.2                200         31         33       0       0
 11:52 Establ
  VR1.inet.0: 0/0/0/0
20.0.0.1                200         10          8       0       0
  2:22 Establ
  VR3.inet.0: 0/0/0/0<-------------NO PREFIXES RECEIVED
20.0.0.2                300          7         10       0       0
  2:22 Establ
  VR2.inet.0: 0/0/0/0

After advertise-inactive:

Groups: 4 Peers: 4 Down peers: 0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last
Up/Dwn State|#Active/Received/Accepted/Damped...
10.0.0.1                100         34         34       0       0
 12:35 Establ
  VR2.inet.0: 0/1/1/0
10.0.0.2                200         33         34       0       0
 12:35 Establ
  VR1.inet.0: 0/0/0/0
20.0.0.1                200         12          9       0       0
  3:05 Establ
  VR3.inet.0: 1/1/1/0<--------------1 PREFIX RECEIVED.
20.0.0.2                300          8         12       0       0
  3:05 Establ
  VR2.inet.0: 0/0/0/0

As you can see no session reset.

/Roger

On Fri, Jul 14, 2017 at 10:02 AM,  <adamv0025 at netconsultings.com> wrote:
>> Chen Jiang
>> Sent: Friday, July 14, 2017 3:51 AM
>>
>> Hi! Experts
>>
>> Sorry for disturbing, I have noticed JUNOS will re-establish BGP neighbour
>> relationship when configuring "advertise-inactive" under a neighbour. But
>> from the packets captured from neighbour peer there is nothing changed
>> when negotiated BGP relationship.
>>
>> I doubt is this a must behaviour when configuring "advertise-inactive" in
>> BGP?
>>
> Because Junos BGP implementation is coming from "hey my home server can now
> talk bgp" so some of the things that would be deemed unthinkable in a
> routing system BGP implementation are normal in Junos, and what's worst
> users don't seem to mind.
>
> Haven't you seen any new capability being advertised? That would be the only
> sensible reason why to drop a session because of this. Though the only thing
> I found was  draft-fletcher-bgp-inactive-path-00.txt
>
>
> adam
>
> netconsultings.com
> ::carrier-class solutions for the telecommunications industry::
>
> _______________________________________________
> juniper-nsp mailing list juniper-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp