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gustkiller
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Does MPLS kills ECMP?

Fri Oct 29, 2010 2:21 pm

Hi,

We have a lot of pops with at least two paths via licensed microwave radios. everything were working fine, ospf making equal cost multipath perfectly.

Yesterday i enabled mpls in our routers and its just killed the equal coast multipath overloading one radio and the second link with almost no traffic.

I checked the routing table on our core routers and they still have two paths ( gateways ) for the destination routes but only one is used with mpls enable.


Any hint?

Thanks
 
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mrz
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 2:24 pm

LDP assigns label only to first gateway from ECMP
 
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 2:45 pm

thanks for the quick answer.

Any way to use mpls and dont loss the equal coast multipath ?
 
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 3:08 pm

ECMP

MPLS supports equal-cost multipath (ECMP) labels. A nonconfigurable maximum of 16 MPLS paths is supported. On LERs, MPLS ECMP next hops can be used in the IP routing table for non-VPN and VPN routes. On LSRs, an incoming label can point to either an MPLS ECMP next hop or an IP ECMP.

The signaling protocol determines whether ECMP next hops are used. For example, LDP can learn multiple labels for a route from different downstream peers (or one label from a downstream peer that has parallel connections to the router). LDP then creates an MPLS ECMP next hop that can be used in the IP routing table. If LDP also advertises a label, then a forwarding entry is added to the MPLS forwarding table with the ECMP next hop.

SOURCE:http://www.juniper.net/techpubs/softwar ... nfig5.html
 
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 3:58 pm

Or any way to use VPLS without LDP ?
 
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 4:02 pm

It is possible to use BGP signaled VPLS
http://wiki.mikrotik.com/wiki/BGP_based_VPLS

TE can be used to steer VPLS tunnels through any link you want.
 
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 4:18 pm

Thanks,

setting up a bgp signaled tunnel now!
 
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Re: Does MPLS kills ECMP?

Fri Oct 29, 2010 4:51 pm

mrz,

something strange is hapenening


i´m testing it with 3 routers , i need a vpls beetwen Router A and Router C

A ---- B ----- C

Router A is a route reflector, router b and c are route reflect clients, ospf is redistributing only loopback address. Bgp redistributing static and conected routes, l2vpn and ipv4 address family enabled.

When i setup bgp signaled vpls, in router C and just after i set the router A. The dynamic vlps appear in router A, but doesnt appear on router C. tried with router B and the same happen.
Router A appear both two dynamic vpls interfaces , but nothing on B an C.


Router A VPLS SETUP ( this one appears two dynamic vpls interfaces)

/interface vpls bgp-vpls
add bridge=PTT-BA bridge-cost=0 bridge-horizon=1 disabled=no \
export-route-targets=1:1 import-route-targets=1:1 name=PTT-BA \
route-distinguisher=1:1 site-id=4

Router B VPLS SETUP (no vpls interface appears)

/interface vpls bgp-vpls
add bridge=vlpsptt_temp bridge-cost=0 bridge-horizon=1 comment="" disabled=no \
export-route-targets=1:1 import-route-targets=1:1 name=PTT-workaround \
route-distinguisher=1:1 site-id=3

Router C VPLS SETUP ( no vpls interface appears)

/interface vpls bgp-vpls
add bridge=bridge1 bridge-cost=0 bridge-horizon=1 comment="" disabled=no \
export-route-targets=1:1 import-route-targets=1:1 name=PTT-BAv4 \
route-distinguisher=1:1 site-id=1
 
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Re: Does MPLS kills ECMP?

Mon Nov 01, 2010 10:20 pm

n1 can help? is really possible to use vpls and Te without LDP enabled? As i said before, the current ldp implementation kills ecmp that is essential for our network.
 
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Re: Does MPLS kills ECMP?

Mon Nov 01, 2010 10:37 pm

We had trouble getting this to work too. We were experiencing some other routing issues and weren't sure what the cause was so we backed out of MPLS, and we haven't gotten back to it, but I remember having lots of problems unless we enabled LDP.
 
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Re: Does MPLS kills ECMP?

Mon Nov 01, 2010 10:52 pm

here a screenshot. ldp disabled. bgp vpls setup and only our core router appears the dynamic mpls interface, the second router doesnt appears the interface.
You do not have the required permissions to view the files attached to this post.
 
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mrz
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Re: Does MPLS kills ECMP?

Tue Nov 02, 2010 8:34 am

n1 can help? is really possible to use vpls and Te without LDP enabled? As i said before, the current ldp implementation kills ecmp that is essential for our network.
No, even BGP based VPLS still needs LDP, but difference with BGP VPLS is that you can force each VPLS to whatever link you want. I'm not sure if this is what you want, but here is an example:
http://wiki.mikrotik.com/wiki/Transpare ... S_extended
 
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Re: Does MPLS kills ECMP?

Tue Nov 02, 2010 3:11 pm

mrz,

thanks for your support, but i think i cant use mpls here, going to stick with Eoip tunnels, because lack of support in ecmp for labels. in our network we have a lot of dual or triple links for redundance and load balancing that is working great using OSPF. the last example you made would work but as a "workaround" solution .

but for us, is better to keep ospf doing the load balance than create the tunel and make de bonding interface to get the result we already have with a simpler solution like ospf ecmp.

do you (mikrotik) have any plans to add support to ecmp labels ( so we can have the same result as ospf ecmp) to forward traffic?

and again, thank you so much and see you in MUM salvador, if u came :)
 
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Re: Does MPLS kills ECMP?

Tue Nov 02, 2010 6:41 pm

No, even BGP based VPLS still needs LDP
Is this still the case if using OSPF MPLS-TE?
 
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Re: Does MPLS kills ECMP?

Tue Nov 02, 2010 8:15 pm

No, even BGP based VPLS still needs LDP
Is this still the case if using OSPF MPLS-TE?
i tried ospf mpls-te and doesnt work either
 
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Re: Does MPLS kills ECMP?

Tue Jul 14, 2020 8:02 pm

Is it still so? LDP chooses the first route in a ECMP situation? Thanks.
 
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Re: Does MPLS kills ECMP?

Fri Jul 17, 2020 9:36 pm

Yeah, actually the only way of achieving something similar to ECMP is with VPLS + TE tunnels, a real ECMP is not possible with RouterOS, I think that some other vendors allow that, but with RouterOS is not doable, actually that's my limitation to deploy LDP in my network because ECMP is a must.

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