Re: Missing labels in T-LDP

Marcel,

There are a few exceptions, but in order to forward labeled packets over an
interface you need "mpls ip" on the interface. A couple of exceptions are
when you are using another protocol to advertise labels over the interface
such as BGP + send-label or RSVP (in MPLS TE). Unlike these scenarios,
targeted hellos do not remove the need for configuring "mpls ip" on an
interface.

Remember, targeted hellos are not only used by session protection. For
example, they are also used in AToM where you need to advertise one label
(VC label) across multiple hops.

On Sun, Oct 11, 2009 at 1:47 AM, Marcel Lammerse <m.lammerse_at_mac.com> wrote:

>
> Hi Bryan,
>
> yeah.. still wondering what's going on here.
>
> Someone suggested to me that targeted ldp is used more for mpls
> applications such as atom, not so much for plain label switching between
> directly connected routers. But, t-ldp is also mentioned as a way of making
> ldp sessions more resilient in case the directly connected interface between
> two ldp peers breaks.
>
> The way I understand it, there are two ways of configuring a protected ldp
> session.
>
> 1. 'mpls ldp neighbor <ip> targeted ldp' in global config mode
>
> 2. 'mpls ip' under the interface + 'mpls ldp session protection' in
> global config mode
>
> So really with ldp session protection, you have both a directly connected
> ldp session and a 'targeted' ldp session active at the same time.
>
> When I try option 1 and remove the 'mpls ip' command from the interface,
> the labels disappear from the lfib, but the targeted ldp sesions is up. If
> leave the 'mpls ip' command on the interface, I do receive the labels.
>
> So my questions are :
>
> 1. Why are there different commands to configure a protected ldp
> session, that seem to do the same thing?
> 2. When should I configure a targeted ldp session and what is it used
> for?
> 3. Why am I not receiving labels across a targeted ldp session between
> directly connected neighbors?
>
> PE4#sh mpls ldp neighbor
> Peer LDP Ident: 1.1.1.1:0; Local LDP Ident 4.4.4.4:0
> TCP connection: 1.1.1.1.646 - 4.4.4.4.13537
> State: Oper; Msgs sent/rcvd: 15/15; Downstream
> Up time: 00:00:15
> LDP discovery sources:
> FastEthernet1/0, Src IP addr: 172.16.14.1
> Addresses bound to peer LDP Ident:
> 1.1.1.1 172.16.12.1 172.16.14.1
> Peer LDP Ident: 3.3.3.3:0; Local LDP Ident 4.4.4.4:0
> TCP connection: 3.3.3.3.646 - 4.4.4.4.14581
> State: Oper; Msgs sent/rcvd: 15/15; Downstream
> Up time: 00:00:13
> LDP discovery sources:
> FastEthernet3/0, Src IP addr: 172.16.34.3
> Addresses bound to peer LDP Ident:
> 3.3.3.3 172.16.13.3 172.16.23.3 172.16.34.3
>
> PE4#sh mpls forwarding-table 192.168.2.0
> Local Outgoing Prefix Bytes Label Outgoing Next Hop
> Label Label or VC or Tunnel Id Switched interface
> 23 25 192.168.2.0/24 0 Fa1/0
> 172.16.14.1
> 19 192.168.2.0/24 0 Fa3/0 172.16.34.3
> PE4#
>
>
> PE4#sh run int fastEthernet 1/0
> Building configuration...
>
> Current configuration : 105 bytes
> !
> interface FastEthernet1/0
> ip address 172.16.14.4 255.255.255.0
> duplex auto
> speed auto
> mpls ip
> end
>
> PE4#sh run int fastEthernet 3/0
> Building configuration...
>
> Current configuration : 105 bytes
> !
> interface FastEthernet3/0
> ip address 172.16.34.4 255.255.255.0
> duplex auto
> speed auto
> mpls ip
> end
>
> PE4#
>
> PE4#conf t
> Enter configuration commands, one per line. End with CNTL/Z.
> PE4(config)#int fastEthernet 3/0
> PE4(config-if)#no mpls ip
> PE4(config)#int fastEthernet 1/0
> PE4(config-if)#no mpls ip
> PE4(config-if)#exit
> PE4(config)#mpls ldp neighbor 1.1.1.1 targeted ldp
> PE4(config)#mpls ldp neighbor 3.3.3.3 targeted ldp
> PE4(config)#
>
> PE4#sh mpls ldp neighbor
> *Oct 11 17:37:53.215: %SYS-5-CONFIG_I: Configured from console by console
> Peer LDP Ident: 3.3.3.3:0; Local LDP Ident 4.4.4.4:0
> TCP connection: 3.3.3.3.646 - 4.4.4.4.28418
> State: Oper; Msgs sent/rcvd: 268/268; Downstream
> Up time: 03:41:25
> LDP discovery sources:
> Targeted Hello 4.4.4.4 -> 3.3.3.3, active, passive
> Addresses bound to peer LDP Ident:
> 3.3.3.3 172.16.13.3 172.16.23.3 172.16.34.3
> Peer LDP Ident: 1.1.1.1:0; Local LDP Ident 4.4.4.4:0
> TCP connection: 1.1.1.1.646 - 4.4.4.4.24502
> State: Oper; Msgs sent/rcvd: 35/36; Downstream
> Up time: 00:18:32
> LDP discovery sources:
> Targeted Hello 4.4.4.4 -> 1.1.1.1, active, passive
> Addresses bound to peer LDP Ident:
> 1.1.1.1 172.16.12.1 172.16.14.1
> PE4#
>
>
> PE4#sh mpls forwarding-table 192.168.2.0
> Local Outgoing Prefix Bytes Label Outgoing Next Hop
> Label Label or VC or Tunnel Id Switched interface
> 23 No Label 192.168.2.0/24 0 Fa1/0
> 172.16.14.1
> No Label 192.168.2.0/24 0 Fa3/0 172.16.34.3
> PE4#
>
> PE4#sh mpls forwarding-table
> Local Outgoing Prefix Bytes Label Outgoing Next Hop
> Label Label or VC or Tunnel Id Switched interface
> 16 No Label 3.3.3.3/32 41402 Fa3/0
> 172.16.34.3
> 17 No Label 2.2.2.2/32 0 Fa1/0
> 172.16.14.1
> No Label 2.2.2.2/32 0 Fa3/0 172.16.34.3
> 18 No Label 1.1.1.1/32 0 Fa1/0
> 172.16.14.1
> 19 No Label 172.16.24.0/24 0 Fa1/0
> 172.16.14.1
> No Label 172.16.24.0/24 0 Fa3/0 172.16.34.3
> 20 No Label 172.16.13.0/24 0 Fa3/0
> 172.16.34.3
> 21 No Label 172.16.12.0/24 0 Fa1/0
> 172.16.14.1
> 22 No Label 172.16.23.0/24 0 Fa3/0
> 172.16.34.3
> 23 No Label 192.168.2.0/24 0 Fa1/0
> 172.16.14.1
> No Label 192.168.2.0/24 0 Fa3/0 172.16.34.3
> 24 No Label 12.12.12.2/32 0 Fa1/0
> 172.16.14.1
> No Label 12.12.12.2/32 0 Fa3/0 172.16.34.3
> PE4#
>
>
> Attached a topology diagram. The link between PE1 and PE2 was shut during
> the lab :
>
> PE4#sh ip int brief
> Interface IP-Address OK? Method Status
> Protocol
> FastEthernet0/0 unassigned YES NVRAM administratively down
> down
> FastEthernet1/0 172.16.14.4 YES NVRAM up
> up
> FastEthernet1/1 unassigned YES NVRAM administratively down
> down
> FastEthernet2/0 172.16.24.4 YES NVRAM administratively down
> down
> FastEthernet2/1 unassigned YES NVRAM administratively down
> down
> FastEthernet3/0 172.16.34.4 YES NVRAM up
> up
> FastEthernet3/1 unassigned YES NVRAM administratively down
> down
> FastEthernet4/0 unassigned YES NVRAM up
> up
> FastEthernet4/1 unassigned YES NVRAM administratively down
> down
> SSLVPN-VIF0 unassigned NO unset up
> up
> Loopback0 4.4.4.4 YES NVRAM up
> up
> PE4#
>
>
>
>
>
> On 11/10/2009, at 10:18 , Bryan Bartik wrote:
>
> Marcel,
>>
>> Are you still having this issue? Can you post configs and topology?
>>
>> On Wed, Oct 7, 2009 at 6:13 PM, Marcel Lammerse <m.lammerse_at_mac.com>
>> wrote:
>>
>> Experts,
>>>
>>> here I have a load-balanced path between directly connected ldp speakers
>>> :
>>>
>>> PE4#sh mpls forwarding-table 192.168.2.0
>>> Local Outgoing Prefix Bytes Label Outgoing Next Hop
>>> Label Label or VC or Tunnel Id Switched interface
>>> 22 25 192.168.2.0/24 0 Fa1/0
>>> 172.16.14.1
>>> 23 192.168.2.0/24 0 Fa3/0 172.16.34.3
>>> PE4#
>>>
>>> PE4#sh mpls ldp bindings 192.168.2.0 24 detail
>>> lib entry: 192.168.2.0/24, rev 22, chkpt: none
>>> local binding: label: 22 (owner LDP)
>>> Advertised to:
>>> 1.1.1.1:0 3.3.3.3:0
>>> remote binding: lsr: 1.1.1.1:0, label: 25
>>> remote binding: lsr: 3.3.3.3:0, label: 23
>>> route information: state: none, table: default,
>>> next-hop: 172.16.14.1, remote label: 25
>>> route information: state: none, table: default,
>>> next-hop: 172.16.34.3, remote label: 23
>>>
>>> If I change the ldp sessions to t-ldp, and keep everything else the same,
>>> the labels seem to disappear and traffic appears to go out untagged :
>>>
>>> PE4#sh mpls forwarding-table 192.168.2.0
>>> Local Outgoing Prefix Bytes Label Outgoing Next Hop
>>> Label Label or VC or Tunnel Id Switched interface
>>> 22 No Label 192.168.2.0/24 0 Fa1/0
>>> 172.16.14.1
>>> No Label 192.168.2.0/24 0 Fa3/0 172.16.34.3
>>> PE4#
>>>
>>> PE4#sh mpls ldp bindings 192.168.2.0 24 detail
>>> lib entry: 192.168.2.0/24, rev 22, chkpt: none
>>> local binding: label: 22 (owner LDP)
>>> Advertised to:
>>> 3.3.3.3:0 1.1.1.1:0
>>> remote binding: lsr: 3.3.3.3:0, label: 23
>>> remote binding: lsr: 1.1.1.1:0, label: 25
>>> route information: state: none, table: default,
>>> next-hop: 172.16.14.1, remote label: <----- no label
>>> route information: state: none, table: default,
>>> next-hop: 172.16.34.3, remote label: <----- no label
>>> PE4#
>>>
>>> I'm a bit confused by this. I would have expected the traffic to continue
>>> to be labeled and the labels to remain the same.
>>>
>>> Can anyone shed some light on why this happens?
>>>
>>> Thanks,
>>> Marcel
>>>
>>>
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>>>
>>>
>>>
>>>
>>>
>>
>> --
>> Bryan Bartik
>> CCIE #23707 (R&S), CCNP
>> Sr. Support Engineer - IPexpert, Inc.
>> URL: http://www.IPexpert.com
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html
>>
>>
>>
>>
>>
>>
>>
>>
>
>

-- 
Bryan Bartik
CCIE #23707 (R&S), CCNP
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com
Blogs and organic groups at http://www.ccie.net