[c-nsp] MPLS router-ID
Mohammad Khalil
eng_mssk at hotmail.com
Fri Aug 14 08:00:54 EDT 2015
Local LDP Identifier:
172.20.40.7:0
Discovery Sources:
Interfaces:
POS9/0/0 (ldp): xmit
Enabled: Interface config
Hello interval: 5000 ms; Transport IP addr: 212.118.1.222
Clients: IPv4
This is my interface of concern , and as u can see the xmit is only functioning on that interface
My case is eBGP case , I have tried it via OSPF and got the point
Thanks
> Date: Thu, 13 Aug 2015 20:00:50 -0400
> From: paul at gtcomm.net
> To: eng_mssk at hotmail.com; jwbensley at gmail.com; cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] MPLS router-ID
>
> LDP transport-address is the address of which you tell the neighbor on
> that interface to send packets. (such as defaults to the router id,
> like a loopback)
> If the loopback, or the router id of the router you are on is not
> present in the IGP on other routers, you use the transport-address to
> tell the other router on that interface to use 'interface' or you can
> specify an IP.
>
> example would be, remove your loopback from being advertised from ospf,
> now no other router knows how to get to your loopback, but the LDP
> router-id is still your loopback, so you override that by setting a
> per-interface IP configuration to tell the neighbor router how to
> establish a session with you
>
> it has nothing to do with the source address of transmitted ldp hellos
> (the udp discovery packets)
> It has to do with the TCP session that is created after discovery.
> example:
> Router1 interface fa0/1 1.1.1.1 IP -> router 2 interface fa0/1 1.1.1.2 IP
> router 1 loopback 5.5.5.5 router2 loopback 6.6.6.6
> router 1 loopback not in IGP router2 loopback in IGP
>
> this happens..:
> router1 send LDP source 1.1.1.1 -> UDP MULTICAST hello
> router2 respond, 1.1.1.2 -> 1.1.1.1 my router id is 6.6.6.6 , I will me
> master and you will be passive
> router1 says OK, my router id 5.5.5.5, make a tcp connection to me
> router 2 can't make a tcp connection to 5.5.5.5 because it's not in the IGP!
>
> and now...router1 interface fa0/1, add transport-address interface
> <<skipping first 2 thing>>
> router1 says OK, my router id(transport address) is 1.1.1.1 make a tcp
> connection to me
> router 2 6.6.6.6 make tcp connection to 1.1.1.1 and all is ok
>
>
> Obviously this is a crude representation of what happens but it should
> show you the value of the transport-address.
>
> you can check the transport addr with show mpls ldp discovery detail
>
>
> On 8/13/2015 5:30 AM, Mohammad Khalil wrote:
> > I lapped it up and the source of the hello messages will be the IP assigned on the physical address , but when the session comes up , the TCP source from my side will be the transport-address
> >
> > BR,
> > Mohammad
> >
> > From: eng_mssk at hotmail.com
> > To: jwbensley at gmail.com; cisco-nsp at puck.nether.net
> > Subject: RE: [c-nsp] MPLS router-ID
> > Date: Thu, 13 Aug 2015 12:10:52 +0300
> >
> >
> >
> >
> >
> > What
> > is so weird is that I have configured the mpls ldp discovery
> > transport-address x.x.x.x and am still seeing the ldp hello messages
> > from my side sourced from the physical IP address , why?
> > BR,
> > Mohammad
> >
> >
> >
> >> From: jwbensley at gmail.com
> >> Date: Tue, 11 Aug 2015 18:44:34 +0100
> >> To: cisco-nsp at puck.nether.net
> >> Subject: Re: [c-nsp] MPLS router-ID
> >>
> >> On 11 August 2015 at 14:39, Mohammad Khalil <eng_mssk at hotmail.com> wrote:
> >>> I have one of my PEs already configured with a router-id (which is my private loopback interface)
> >> I assume you mean LDP router-id?
> >>
> >>> Am trying to establish xconnect with my uplink provider (which uses Juniper)
> >>> The SP insisted to use public IP address for LDP neighborship , I cannot change my router-id as I will lose all of my active L2VPN sessions in my network (according to what I know , I cannot have expect for one ID for my router)
> >>> I configured a public IP address and advertised it into BGP to my SP and the MPLS LDP session is up , but the targeted LDP session is passive !
> >> What you say configured a public IP, do you mean on the interface
> >> facing the provider and then used something like "discovery
> >> transport-address interface" to use the interface IP as your LDP
> >> router-id?
> >>
> >> Also why have you originated it into BGP? If you are using the public
> >> on on the interface facing your provider they should know IP because
> >> its directly connected.
> >>
> >> On paper this configuration works but I'm not 100% clear of your explentaion.
> >>
> >> As Nick has said, just having something like a tagged sub-interface
> >> between you and your provider where the xconnect terminates would be a
> >> better idea, the L3 VPNs can be in other sub-int's.
> >>
> >> Cheers,
> >> James.
> >> _______________________________________________
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> >
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>
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