Routing
Routing

CSPF and Inter-Area OSPF

4 weeks ago

Hej

I was looking for some clarification on RSVP CSPF and Multi-Area OSPF configuration.

When reading on the CSPF and Inter-AREA TE, it sounds like it should not be possible to establish a RSVP path that traverses different OSPF areas. And that I would need "expand-loose-hops + inter-domain" configured to achieve TE in such a scenario.

 

But in my testing I have not seen different OSPF areas having any affect on CSPF calculations.


for example below is one such quote

Also of note is that you will be unable to use CSPF to calculate a full, end-to-end path, when the network contains multiple TE domains—that is, more than one TED view. Such a condition can arise when a network has multiple routing domains, or in the case of a Multi-Level or Multi-Area IS-IS or OSPF network, respectively, because TE information is not leaked between IS-IS levels or OSPF areas.

When building LSPs that cross multiple TE domains, your best bet is to disable CSPF and use plain old EROs.

However, when I test in my lab, I can see that when I configure an admin group on an LSP that traverses between OSPF area 0 and 1, the Admin-group constraint is honored. This sounds contradictory to the descriptions regarding inter-area TE.

 

CSPF to follow Admin group BLUE

10.220.1.3
*Primary State: Up
Priorities: 7 0
OptimizeTimer: 30
SmartOptimizeTimer: 180
Include Any: blue
Flap Count: 1
MBB Count: 0
Reoptimization in 28 second(s).
Computed ERO (S [L] denotes strict [loose] hops): (CSPF metric: 40)
10.220.14.1 S 10.220.12.2 S 10.220.26.2 S 10.220.36.1 S 
Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
10.220.14.1(Label=294) 10.220.12.2(Label=359) 10.220.26.2(Label=261) 10.220.36.1(Label=0)

 

NO-CSPF

10.220.1.3
From: 10.220.1.4, State: Up, ActiveRoute: 0, LSPname: r4-to-r3
*Primary State: Up
Priorities: 7 0
Bandwidth: 700Mbps
OptimizeTimer: 30
SmartOptimizeTimer: 180
Include Any: blue
Flap Count: 0
MBB Count: 0
Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
10.220.14.1(Label=292) 10.220.12.2(Label=357) 10.220.23.2(Label=0)
Originate make-before-break call: Add skipped CSPF run

Regards
Oscar

7 REPLIES 7
Routing

Re: CSPF and Inter-Area OSPF

3 weeks ago

Hi Oscar,

 

Are you sure the RRO shows hops in different areas? Please share the device model/Junos version and how the LSP spans across areas.

 

Hope this helps.

Regards,
-r.

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Routing

Re: CSPF and Inter-Area OSPF

3 weeks ago

@mriyaz

I am running Logical systems on a MX104 version 18.4R2:

The LSP starts at R4 in Area 1 and goes to Area 0. 

With No-CSPF the RRO follows the IGP which is R4-R1-R2-R3

With CSPF the RRO follow blue link thich is R4-R1-R2-R6-R3. And this is where my initial question comes in. 

 

Multi-Area-CSPF.PNG

Routing

Re: CSPF and Inter-Area OSPF

3 weeks ago

Hello Oscar,

 

Thought we at least needed "inter-domain" in the LSP.  Or use LSP stitching/tunnelling.  Mind to share the config used here, especially for the LSP under mpls/rsvp?

 

Hope this helps.

 

Regards,
-r.

--------------------------------------------------

If this solves your problem, please mark this post as "Accepted Solution."
Kudos are always appreciated Smiley Happy.

 

 

Routing

Re: CSPF and Inter-Area OSPF

3 weeks ago

 

Here you go


OSPF

R4# show protocols ospf   
traffic-engineering;
external-preference 149;
export OSPF-EXPORT;
area 0.0.0.1 {
    nssa;
    interface lo0.4;
    interface ge-1/1/4.14 {  >>>>>>>This neighbor is the ABR to area 0
        interface-type p2p;
		


RSVP

odj@test3pe1dk:Oscar-Lab-R4# show 
traceoptions {
    file cspf;
    flag cspf;
    flag cspf-link;
    flag cspf-node;
}
admin-groups {
    blue 0;
    red 1;
}
explicit-null;
icmp-tunneling;                        
label-switched-path TO-R3 {
    to 10.220.1.3;
    optimize-timer 30;
    admin-group include-any blue;
    }
}
interface ge-1/1/4.14 {
    admin-group blue;
}

 

Routing

Re: CSPF and Inter-Area OSPF

3 weeks ago

I have done a bit more digging but wherever I read, it sounds like LSP with constraints like Admin groups should not be forming without Interdomain.

Does any one faced this before?

Routing

Re: CSPF and Inter-Area OSPF

Monday

The CSPF computation cannot span multiple areas or multiple levels because CSPF relies on the traffic engineering database to provide user specified constraints like BW, EROs, and admin-groups. Without inter-domain or no-cspf, the LSP won't come up across area.

Thank You,
SuSi
Routing

Re: CSPF and Inter-Area OSPF

Tuesday

Hej Sivas

Based on all the documentation I would agree with you. But regardless of it I have the LSP established and it even takes CPF into account.

Does anything from the outputs above catches your eye?

Regards

Oscar