Routing
Routing

To understand RSVP LDP tunnel link !

‎08-08-2019 03:11 AM

Hi everyone,

I have the lab topology:

topology.PNG

 

In table inet.3 of R1, I can see that R1 always chose RSVP tunnel between R1-R3 to reach R4, R5, R6 instead of other paths.

Can anyone help me to explain this behavior?

Is there any way to load-balancing between R1-R3 RSVP tunnel and R1-R2 RSVP-LDP tunnel to reach R4, R5, R6 ?

 

 

lab@LAB_ANGOC# run show route table inet.3 logical-system R1

inet.3: 12 destinations, 19 routes (5 active, 0 holddown, 12 hidden)
+ = Active Route, - = Last Active, * = Both

10.200.4.1/32 *[RSVP/7/1] 00:00:13, metric 20
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
[LDP/9] 00:00:13, metric 20
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
10.200.4.8/32 *[LDP/9] 00:00:13, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
10.200.4.32/32 *[LDP/9] 00:00:13, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
10.200.4.33/32 *[LDP/9] 00:00:13, metric 40
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
10.200.8.1/32 *[RSVP/7/1] 01:30:25, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
[LDP/9] 01:15:55, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2

 

I include the lab configuration too. Thanks alot!

 

 

Attachments

11 REPLIES 11
Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 05:55 AM

I think you need to play around with metric for load balancing to work .  Try configuring the same metric for both the LSPs as shown below : 

 

set logical-systems R1 protocols mpls label-switched-path TO-R2 metric 30 

set logical-systems R1 protocols mpls label-switched-path TO-R3 metric 30 

If the above don't work try to find the right metric combination Smiley Happy 

Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 06:31 AM

From your topology, it doesn't make sense to LB between R1-R3 and R1-R2 LSP, unless you add another link between R2 and R4. Then you can play around with the metric 


Mengzhe Hu
JNCIE x 3 (SP DC ENT)
Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 06:37 AM

Hi jibut,

I tried to set the metric of R1-R3 LSP to 30 .The LDP route now turn to TO-R2 LSP tunnel path and we can see that the metric from R1 to R4, R5, R6 is the same with the first situation.

 

run show route table inet.3 logical-system R1
Aug 08 17:42:53

inet.3: 12 destinations, 19 routes (5 active, 0 holddown, 12 hidden)
+ = Active Route, - = Last Active, * = Both

10.200.4.1/32 *[RSVP/7/1] 00:04:11, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
[LDP/9] 00:00:09, metric 20
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
10.200.4.8/32 *[LDP/9] 00:00:09, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
10.200.4.32/32 *[LDP/9] 00:00:09, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
10.200.4.33/32 *[LDP/9] 00:00:09, metric 40
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
10.200.8.1/32 *[RSVP/7/1] 00:00:09, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
[LDP/9] 00:00:09, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2

 

When i set the metric of both R1-R2 LSP and R1-R3 LSP to 30, the LDP route now turn to LDP that follow IGP path, and the metric from R1 to R4, R5, R6 is the same with the first situation.

lab@LAB_ANGOC# run show route table inet.3 logical-system R1
Aug 08 17:54:27

inet.3: 5 destinations, 7 routes (5 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

10.200.4.1/32 *[RSVP/7/1] 00:15:45, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R3
[LDP/9] 00:00:10, metric 20
> to 10.0.2.1 via ge-0/0/2.2, Push 299776
10.200.4.8/32 *[LDP/9] 00:00:10, metric 30
> to 10.0.2.1 via ge-0/0/2.2, Push 299792
10.200.4.32/32 *[LDP/9] 00:00:10, metric 30
> to 10.0.2.1 via ge-0/0/2.2, Push 299840
10.200.4.33/32 *[LDP/9] 00:00:10, metric 40
> to 10.0.2.1 via ge-0/0/2.2, Push 299808
10.200.8.1/32 *[RSVP/7/1] 00:00:11, metric 30
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
[LDP/9] 00:00:10, metric 10
> to 10.0.2.1 via ge-0/0/2.2, Push 0

 
Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 07:22 AM

@mhu wrote:

From your topology, it doesn't make sense to LB between R1-R3 and R1-R2 LSP, unless you add another link between R2 and R4. Then you can play around with the metric 


Hi mhu,

I have a little change for the topology to make sense of load-balancing: 2 LSPs from R1 have the strict path (TO-R2 LSP get the first path and TO-R3 LSP get the second path). But the result does not change.

lab@LAB_ANGOC# run show mpls lsp ingress logical-system R1
Aug 08 18:41:04
Ingress LSP: 2 sessions
To From State Rt P ActivePath LSPname
10.200.4.1 10.200.8.46 Up 0 * LINK-2 TO-R3
10.200.8.1 10.200.8.46 Up 0 * LINK-1 TO-R2

 

lab@LAB_ANGOC# run show route table inet.3 logical-system R1
Aug 08 18:41:59

inet.3: 12 destinations, 19 routes (5 active, 0 holddown, 12 hidden)
+ = Active Route, - = Last Active, * = Both

10.200.4.1/32 *[RSVP/7/1] 00:05:52, metric 20
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
[LDP/9] 00:05:52, metric 20
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.4.8/32 *[LDP/9] 00:05:52, metric 30
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.4.32/32 *[LDP/9] 00:05:52, metric 30
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.4.33/32 *[LDP/9] 00:05:52, metric 40
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.8.1/32 *[RSVP/7/1] 00:12:53, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
[LDP/9] 00:05:06, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2

 

Capture.PNG

 
Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 05:13 PM

Initially I am thinking that you might not have applied LBPP under each logical-system. But that looks correct. You always have one next-hop in any combination. My guess is, eventually we need to evaluate the IGP metric to consider ECMP. However there's always a difference between R1-R2 and R1-R3. 

Come across this, try if this can help

https://www.juniper.net/documentation/en_US/junos13.1/information-products/topic-collections/nog-mpl...


Mengzhe Hu
JNCIE x 3 (SP DC ENT)
Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 05:59 PM

i can see same symptom in my lab. While I still challege your use case, because eventually it is going through one next-hop interface to same physical neighor, let me try in my lab and see how/if I can make it work as you desire 


Mengzhe Hu
JNCIE x 3 (SP DC ENT)
Routing

Re: To understand RSVP LDP tunnel link !

‎08-08-2019 07:08 PM

@mhu wrote:

Initially I am thinking that you might not have applied LBPP under each logical-system. But that looks correct. You always have one next-hop in any combination. My guess is, eventually we need to evaluate the IGP metric to consider ECMP. However there's always a difference between R1-R2 and R1-R3. 

Come across this, try if this can help

https://www.juniper.net/documentation/en_US/junos13.1/information-products/topic-collections/nog-mpl...


Hi mhu,

Thanks for your reply. I have checked your document, but that topic is about load-balancing between two hops that the Ingress router has multi LSPs to the Egress router.

In my case, LSPs are just the tunnel with LDP tunneling enabled (they do not get to the end hop directly). And the route in inet.3 of R1 to the end router actually follow the LDP.

 
Routing

Re: To understand RSVP LDP tunnel link !

‎08-12-2019 05:05 PM

Not able to find a way to make it work. Let's take R1-R2-R3-R6 as example. I have put IGP metric as 10 on all links

By default, on R1, ldp route to R6 takes R1-R3 LSP. If I keep increasing the LSP R1-R3 metric, it still chooses R1-R3 till 20. When R1-R3 Metric was changed to 21, it starts to choose R1-R2 LSP. My point is, there's no metric in between 20 and 21 to make is even. I don't think we can make it work through metics.

 

Let's see if anyone else has any other inputs 


Mengzhe Hu
JNCIE x 3 (SP DC ENT)
Highlighted
Routing

Re: To understand RSVP LDP tunnel link !

‎08-12-2019 07:00 PM

@mhu wrote:

Not able to find a way to make it work. Let's take R1-R2-R3-R6 as example. I have put IGP metric as 10 on all links

By default, on R1, ldp route to R6 takes R1-R3 LSP. If I keep increasing the LSP R1-R3 metric, it still chooses R1-R3 till 20. When R1-R3 Metric was changed to 21, it starts to choose R1-R2 LSP. My point is, there's no metric in between 20 and 21 to make is even. I don't think we can make it work through metics.

 

Let's see if anyone else has any other inputs 


Hi mhu,

Thanks for your information, that is exactly what i do with my lab. R1 always prefer R1-R3 LSP to other paths if they have the same metric.

 
Routing

Re: To understand RSVP LDP tunnel link !

‎08-13-2019 08:24 AM

Hi TuanAnhVu and Mhu,

has-key is an important factor in decindg the load balancing. Please confirm if you have hash-key or enhanced-key configuration under forwarding-option?

I  Came acorss following KB

https://kb.juniper.net/KB12995

Can you please check what has-key is used under forwarding-option for protocol MPLS

Thanks
Vishal

Routing

Re: To understand RSVP LDP tunnel link !

‎08-20-2019 08:50 AM

H


@vlsingh wrote:

Hi TuanAnhVu and Mhu,

has-key is an important factor in decindg the load balancing. Please confirm if you have hash-key or enhanced-key configuration under forwarding-option?

I  Came acorss following KB

https://kb.juniper.net/KB12995

Can you please check what has-key is used under forwarding-option for protocol MPLS

Thanks
Vishal


Hi Vishal,

I try to conf the hash-key:

show configuration forwarding-options
Aug 16 06:57:52
hash-key {
family mpls {
label-1;
label-2;
payload {
ip;
}
}
}

 

But it still cant not be share between 2 LSP LDP tunneling.

 

show route table inet.3 logical-system R1
Aug 16 06:58:50

inet.3: 13 destinations, 20 routes (5 active, 0 holddown, 13 hidden)
+ = Active Route, - = Last Active, * = Both

10.200.4.1/32 *[RSVP/7/1] 06:53:44, metric 20
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
[LDP/9] 06:53:27, metric 20
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.4.8/32 *[LDP/9] 06:53:27, metric 30
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.4.32/32 *[LDP/9] 06:53:27, metric 30
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.4.33/32 *[LDP/9] 06:53:27, metric 40
> to 10.0.12.1 via ge-0/0/2.12, label-switched-path TO-R3
10.200.8.1/32 *[RSVP/7/1] 06:53:44, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2
[LDP/9] 06:53:44, metric 10
> to 10.0.2.1 via ge-0/0/2.2, label-switched-path TO-R2