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[MPLS L2Circuit] - non-flow-aware l2circuit signalled over which core link in ECMP

‎03-04-2020 01:12 AM

Hi everybody,

 

I have layer2 circuit configured between two edge routers and no flow labels are in place, and I have two P rotuers in between as below:

 

PE--P==P--PE

 

I need to know over which of the ECMPs between the two P routers this l2circuit is going in each direction.

 

l2circuit {
neighbor 1.0.0.1 {
    interface ge-1/0/0.11 {
        virtual-circuit-id 11;         
        mtu 9100;
        encapsulation-type ethernet;
        pseudowire-status-tlv;
    }
}

 

BR,

MP

3 REPLIES 3
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Re: [MPLS L2Circuit] - non-flow-aware l2circuit signalled over which core link in ECMP

‎03-04-2020 03:33 AM

Hello,

Are P routers from Juniper? If yes what is the P router HW model and JUNOS version?

L2circuit traffic can still be balanced even without flow label if the P router is Juniper MX with Trio (MPC) linecards

https://www.juniper.net/documentation/en_US/junos/topics/concept/mpls-encapsulated-payload-load-bala...

 

In case of multiple transport layer networks such as Ethernet over MPLS or Ethernet pseudowire, the hash algorithm needs to look beyond the outer header of the payload and into the inner headers to generate an even distribution. To determine the inner encapsulation, the PFE relies on the presence of certain codes or numbers at fixed payload offets; for example the presence of payload type 0X800 or the presence of protocol number 4 for an IPv4 packet. 

 

And this is default behaviour, You need to disable it on MX to NOT load-balance the L2circuit traffic in the core.

HTH

Thanks

Alex

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Re: [MPLS L2Circuit] - non-flow-aware l2circuit signalled over which core link in ECMP

‎03-08-2020 05:54 AM

Hello Aarseniev,

 

Thanks for the reply, I guess the document you referred to is quite new, however it is worth trying (after doing some junos upgrades).

 

Anyway, considering the old configuration, or even cisco pe routers with no flow labels, can know over which ECMP links the Ethernet l2circuit is signalled assuming the l2circuit traffic won't be load-shared (as the load sharing decision will be according to the inner label that is significant to the l2circuit)?

 

BR,

MP 

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Re: [MPLS L2Circuit] - non-flow-aware l2circuit signalled over which core link in ECMP

‎03-08-2020 09:45 PM

Hello,

 


@MPellegrini wrote:

 

Anyway, considering the old configuration, or even cisco pe routers with no flow labels, can know over which ECMP links the Ethernet l2circuit is signalled


 

For that bit You have to ask Cisco what ECMP link their PE router chooses for outgoing self-generated targeted LDP packets. But this is meaningless since P routers can choose totally different ECMP link for incoming targeted LDP packets.

 

 


@MPellegrini wrote:

 

assuming the l2circuit traffic won't be load-shared (as the load sharing decision will be according to the inner label that is significant to the l2circuit)?

 



If Your P routers are old M-series/T-series routers or MX with load-balancing based on L2circuit payload lookup disabled, then there is  no supported way to know from JUNOS CLI what ECMP core link will be used for a given L2circuit.

 

HTH

Thx

Alex

 

_____________________________________________________________________

Please ask Your Juniper account team about Juniper Professional Services offerings.
Juniper PS can design, test & build the network/part of the network as per Your requirements

+++++++++++++++++++++++++++++++++++++++++++++

Accept as Solution = cool !
Accept as Solution+Kudo = You are a Star !