The MPLS WG Archive

[Marc Binderberger <marc@sniff.de>]

Hi Roger,

> As you said, this could have some scaling limitations. Does LDP assign 
> a label to each route learnt by the IGP. I think, LDP does not assign 
> labels for BGP Learnt routes. Can cisco be configured to send labels 
> for some BGP Learnt routes?


 From a test setup. The box is a 7507 w/ 12.0(25)S1:

router bgp 65017
  bgp router-id 192.168.249.250
  bgp cluster-id 3239121353
  bgp log-neighbor-changes
  bgp deterministic-med
  bgp bestpath compare-routerid
  neighbor 192.168.249.17 remote-as 65018
  neighbor 192.168.249.17 password 7 070D2D4D460B151015100E1E4A6465
  !
  address-family ipv4
  redistribute isis TEST level-2 route-map ISIS-TO-BGP
  neighbor 192.168.249.17 activate
  neighbor 192.168.249.17 send-label
  no auto-summary
  no synchronization
  exit-address-family


R1-7507#show ip bgp
BGP table version is 4, local router ID is 192.168.249.250
Status codes: s suppressed, d damped, h history, * valid, > best, i - 
internal,
               S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

    Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.249.251/32
                     192.168.249.46          10         32768 ?
*> 192.168.17.206/32
                     192.168.249.17          10             0 65018 ?

R1-7507#show ip bgp 192.168.17.206/32
BGP routing table entry for 192.168.17.206/32, version 4
Paths: (1 available, best #1)
   Not advertised to any peer
   65018
     192.168.249.17 from 192.168.249.17 (192.168.249.241)
       Origin incomplete, metric 10, localpref 100, valid, external, 
best,
       mpls labels in/out 106/18


So R1 receives label "18" via eBGP, the LDP binds local label "106". 
This happens even without a redistribution into the IGP.

On router "R3" (belonging to AS65017):

R3-7204#show mpls ldp bindings 192.168.17.206 32 detail
   tib entry: 192.168.17.206/32, rev 37
         local binding:  tag: 203
           Advertised to:
           192.168.249.250:0
         remote binding: tsr: 192.168.249.250:0, tag: 106


BTW, with 12.2(18)S it did not work.



>> Using iBGP IPv4+label - haven't tested yet as no IOS for 7600 (our PE
>> plattform) was available supporting this. As I understand the theory
>> this results in a packet with 3 labels minimum: the MP-BGP VPN label 
>> at
>> the bottom, then the IPv4 next hop label and topmost the LDP label to
>> the ASBR.
>
> The IPv4 Nexthop Label (Middle one) would be assigned by the ASBR?

Yes. But let me try to get 1-2 more test boxes in the setup. Seeing is 
believing :-)


Regards, Marc
--
Marc Binderberger    <marc@sniff.de>    Powered by *BSD ;-)