[j-nsp] conditional route import

[adamv0025 at netconsultings.com]

Ok got you now, so if I get route X to a “RR” and modify its attributes based on existence of route Y on export to other PEs including the PE that was supposed to introduce the route in the first place, then that would work. 

But route X is actually used for forwarding, so it would have to have its NH altered to point to the PE that was supposed to advertise it.

And a copy of route X for PE that was supposed to introduce it –would have to have its next hop altered to point to the egress interface.

 

Ok so this is how it would work for the very basic functionality, i.e. if route Y exist then alter attributes of a route X that is being introduced to a local AS.

Ok so if I kept these trigger routes in a separate trigger VRF, I could use say: 

1.1.1.120 –to set LP=120

1.1.1.80 –to set LP=80

1.1.2.200 –to set MED=200

 

But for a more complex case where route Y is not just some made up trigger route but actual forwarding route where one would like to be looking at its attributes like IGP metric to a NH, then RR might have a different view than the PE that was supposed to introduce the route into a local AS.

adam  

 

netconsultings.com

::carrier-class solutions for the telecommunications industry::

 

From: Alexander Arseniev [mailto:arseniev at btinternet.com] 
Sent: Wednesday, March 15, 2017 4:16 PM
To: adamv0025 at netconsultings.com; juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] conditional route import

 

My idea is based on what is working in JUNOS today, it is called "conditional EXPORT". 

Yes, unmodified route would be visible only on RR and not used for actual forwarding, that's the purpose of modifying it in 1st place, isn't it?

Your idea to make route attribute change to work conditionally on IMPORT requires adding code to JUNOS.

Your choice what You want to use and when :-)

Thx

Alex

 

On 15/03/2017 10:23, adamv0025 at netconsultings.com <mailto:adamv0025 at netconsultings.com>  wrote:

Although I’d prefer that the router which introduces the route X to a local AS performs the desired attribute changes to the route X, it doesn’t matter whether it’s the PE or a RR –still the same requirement holds true.

PE or RR(in your example) needs to look into its routing table to see if route Y exist and based on that change attributes of an incoming route X.

Yes I could change attributes of route X while I advertise it to RRs (on export from VRF). 

-          but that would make the PE which introduced route X to a local AS oblivion to routing change that’s apparent to everyone else in the AS, which is not desirable    

 

adam

 

netconsultings.com

::carrier-class solutions for the telecommunications industry::

 

From: Alexander Arseniev [mailto:arseniev at btinternet.com] 
Sent: Tuesday, March 14, 2017 5:57 PM
To: adamv0025 at netconsultings.com <mailto:adamv0025 at netconsultings.com> ; juniper-nsp at puck.nether.net <mailto:juniper-nsp at puck.nether.net> 
Subject: Re: [j-nsp] conditional route import

 

Hello,

If You pass this route to BGP RR and do modifications there before advertising it to target PE, where it is installed with modified parameters then You'd achieve Your objective.

BGP RR in this case plays the role of "external controller".

You can even have interface peering extended to BGP RR via L2circuit so PE does not even learn the original route, it installs modified one. This avoids the complexities with sending the modified route back to originator PE I mentioned earlier.

Hope this makes sense.

Thx

Alex

 

 

 

On 14/03/2017 11:23, adamv0025 at netconsultings.com <mailto:adamv0025 at netconsultings.com>  wrote:

Hi Alexander,

 

No in my example I need to modify parameters of route X, based on parameters of route Y.  

That seem to be impossible in current versions of network codes (other than via external controller)

 

adam

 

netconsultings.com

::carrier-class solutions for the telecommunications industry::

 

From: Alexander Arseniev [mailto:arseniev at btinternet.com] 
Sent: Monday, March 13, 2017 12:28 PM
To: adamv0025 at netconsultings.com <mailto:adamv0025 at netconsultings.com> ; juniper-nsp at puck.nether.net <mailto:juniper-nsp at puck.nether.net> 
Subject: Re: [j-nsp] conditional route import

 

Hello,

You can do it easily in BGP Route Reflector export policy coupled with other features like ORR and NH rewriting.

There could be complexities with PE config (obviously, the PE would prefer eBGP route direct from CE vs iBGP from RR) but they can be overcome with routing-instances.

HTH
Thx
Alex

On 12/03/2017 10:32, adamv0025 at netconsultings.com <mailto:adamv0025 at netconsultings.com>  wrote:

Hi folks, 
 
Anyone tried to use "if-route-exists" or the "rib has route" condition for
route import as opposed to the more usual route export or default route
origination respectively? 
Can't find it documented anywhere and it's not working, but I'm just curious
what are your thoughts on the concept of general routing behaviour
programmability using routing information. 
I need the network to reprogram itself based on routing events without the
YANG/NETCONF complexity. 
And for that I'd need a route and it's specific parameter or a set of
parameters to be used as an instruction or a trigger. 
I'd like to be able to use a more general from of condition in
routing-policies (or even forwarding filters or QOS-policies). 
 
Example: 
 
condition_1 
if (route = x.x.x.x/x in VRF A) AND (igp metric to NH < 100)  
then
condition_1 == TRUE
 
route-policy 1
if 
route = y.y.y.y/y AND if condition_1 == TRUE  
then 
set local-preference 120 AND accept 
 
bgp
VRF A neighbour z.z.z.z route-policy 1 in
 
 
 
Options:  
The trigger route can be constructed at the trigger router and advertised
into an intended VRF or to a separate "instructions-VRF", dedicated to
contain these special purpose routes if we don't want to mix these
instruction routes with regular routing information. 
Or the trigger route could be a regular routing info with a specific set of
attributes that we intend to use as a marker of a specific network event
that we want to act upon in case it happens.  
 
 
I'd appreciate any feedback. 
 
 
adam
 
netconsultings.com
::carrier-class solutions for the telecommunications industry::
 
 
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