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MPLS PE S6730 Label Issue

Created: Feb 28, 2020 00:22:29Latest reply: Feb 28, 2020 18:15:13 263 9 0 0
  Rewarded HiCoins: 1 (problem resolved)

Hi,


In the last days our IT team is trying to deploy a S6730-H24X6C as a PE in our MPLS cloud.


The idea is to connect our CDN in that PE and advertise BGP customers routes to that CDN.


At first, we completed the config, everything seemed ok. After analising the traffic, we noticed PE wasn't adding label to P to forward traffic based on LSP. 


This way, without labels, P was using the last resource (OSPF default route) to deliver the packets to destination (customer IP).


This strange behaviour overloaded the edge router (that generates the OSPF default route), all traffic coming from CDN was diverted to  edge router.


The path from CDN to customer was CDN > C > D > B > A > B again > D again > E > F > Customer


Customer --- F (PE) --- E --- D --- C (PE) --- CDN

                                              |

                                             B

                                              |

                                             A (PE) edge router



Is there a known bug in S6730 about this behaviour?


Any suggestion about this scenario?


Thank You!

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Featured Answers
Created Feb 28, 2020 15:59:15 Helpful(0) Helpful(0)

Hi
Let me ask a question.
Are you using vpn to carry this traffic  or just mpls label?

If you aren't using l3vpn nor l2vpn, pls check out this thread and in the and there are two reference so that you would solve your issue.

https://forum.huawei.com/enterprise/en/mpls-label-forwarding/thread/472331-865
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chenhui Admin Created Feb 28, 2020 00:42:53 Helpful(0) Helpful(0)

Hi @ptomasi,
(we noticed PE wasn't adding label to P to forward traffic based on LSP. ) ------- Is the P router the router D in the topology?
Kindly check the FIB on router S6730(router F) if the tunnel ID of traffic to the customer network is 0 or not.
Also, kindly check on router S6730(router F) if there is LSP towards router C.
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ptomasi Created Feb 28, 2020 02:08:41 Helpful(0) Helpful(0)

Hi,

You're right. C (PE) isn't adding label to D (P) when try to forward traffic to customer behind F (PE);

Then, D uses OSPF default route to send traffic to F - this way forcing packet to go to edge router first. After packet reaches edge router it's guided through a LSP from A to F.

I forgot to mention that:
> both C an F have BGP session to A (that acts like edge router and RR);
> C has a label 2771 in LFIB assigned to F loopack;
> Traffic to hosts present in OSPF table uses LSP; traffic to hosts present in BGP table (even through recursivity to remote loopbacks) uses pure IP routing (without labels) until reach edge router;

Could you, kindly, guide me to the troubleshooting commands about these two suggestions? I have no experience yet with troubleshooting commands in Huawei Platform:
> Kindly check the FIB on router S6730(router F) if the tunnel ID of traffic to the customer network is 0 or not.
> Also, kindly check on router S6730(router F) if there is LSP towards router C.

Thanks!
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chenhui Admin Created Feb 28, 2020 07:31:04 Helpful(0) Helpful(0)

Posted by ptomasi at 2020-02-28 02:08 Hi,You're right. C (PE) isn't adding label to D (P) when try to forward traffic to customer behind F ...

Hi,

from your description, the tunnel ID of the entry which destination is the customer behind F should be 0x0, you can check it through command display fib, or display fib vpn-instance VPN-INSTANCE-NAME (for the vpn-instance fib table) 

example as below:

<HUAWEI> display fib

Route Flags: G - Gateway Route, H - Host Route,    U - Up Route                                 

Destination/Mask      Nexthop       Flag  TimeStamp  Interface      TunnelID  
192.168.150.111/32 127.0.0.1       HU    t[117]          InLoop0        0x0


Kindly confirm questions below:

  1. Are you configuring the BGP/MPLS VPN?

  2. Please refer the figure below, if I mark the traffic correctly.


    traffic flow


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ptomasi Created Feb 28, 2020 12:27:01 Helpful(0) Helpful(0)

Hi,


You're right again:


display fib W.X.Y.13
  Route Entry Count: 1
Destination/Mask   Nexthop         Flag  TimeStamp     Interface      TunnelID
W.X.Y.0/24         172.16.3.45     DGU   t[682857]     XGE0/0/11      0x0


TunnelID to BGP customer route is 0x0


Kindly confirm questions below:

  1. Are you configuring the BGP/MPLS VPN?

    > At now, we're deploying only basic OSPF and MPLS cloud. No VPN involved in the scenario yet.


  2. Please refer the figure below, if I mark the traffic correctly.

    > Your diagram is correct: traffic from C > D > B > A has no labels | traffic from A to F follows LSP correctly.


Customer --- F (PE) --- E --- D --- C (PE) --- CDN
                              |
                              B
                              |
                              A (PE) edge router


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welisson_br Created Feb 28, 2020 15:59:15 Helpful(0) Helpful(0)

Hi
Let me ask a question.
Are you using vpn to carry this traffic  or just mpls label?

If you aren't using l3vpn nor l2vpn, pls check out this thread and in the and there are two reference so that you would solve your issue.

https://forum.huawei.com/enterprise/en/mpls-label-forwarding/thread/472331-865
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ptomasi Created Feb 28, 2020 17:15:50 Helpful(0) Helpful(0)

Hi,

We're using only MPLS labels (basic scenario, LDP is managing the label distribution). No VPN (VRF, VPLS, VC, VSI) for now, but planned to future implementation.

I noticed C (PE) has a label in LFIB assigned to F (PE) loopback (to resolve the iBGP route next-hop), but it seems it isn't applying that label when forward the packet to D (P) router.


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ptomasi Created Feb 28, 2020 17:50:00 Helpful(0) Helpful(0)

i_f48.gif


It seems it was solved


https://forum.huawei.com/enterprise/en/bgp-free-core/thread/581954-863 - Thanks to Sprout for that great post and examples


As soon as the command below was applied, traffic was guided to C > D > E > F > Customer through LSP:


route recursive-lookup tunnel


Now, PE C resolves iBGP next-hop and applies correspondent label to it.


Thanks to everyone :-)

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azkasaqib Created Feb 28, 2020 18:15:05 Helpful(0) Helpful(0)

hmmm
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azkasaqib Created Feb 28, 2020 18:15:13 Helpful(0) Helpful(0)

Good
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