http://cciebible.com/ccie-rs-350-001-qas-implement-mpls-layer-3-vpns-1-5/
On Sun, Apr 7, 2013 at 5:00 PM, Nicola Arnoldi <[email protected]>wrote: > Yes, re-reading your problem clearly shows that I was wrong, and your > assumption is totally correct. > You advertise an implicit-null whenever you have to perform an IP lookup > at the E-LSR. > > After a bit of Googling, I can guess your question comes from the various > exam dumps you can find on the Internet, which claim that the statement > "PHP is used only for directly connected subnets or aggregate routes" is > wrong. > > That's a good spot, however. > > > > On Sun, Apr 7, 2013 at 4:49 PM, Nicola Arnoldi > <[email protected]>wrote: > >> try reading this >> >> http://blog.ioshints.info/2011/07/penultimate-hop-popping-php-demystified.html >> >> >> On Sun, Apr 7, 2013 at 4:15 PM, Narendra Naukwal >> <[email protected]>wrote: >> >>> Hi, >>> >>> Thanks for looking into, however, I am not sure if i understand it >>> completly. >>> My question is For what routes will a PE advertise an IMPLICIT NULL >>> label? >>> I know it does advertises Implicit null (LDP value 3 or TDP Value 1) for >>> prefixes that need an IP lookup on the PE itslef. >>> The only route types that come to my mind are route 'Connected'on PE & >>> Routes 'Aggregated'for PE. >>> >>> By the way a router will generate a MPLS label for every prefix >>> installed in RIB via IGP. This I beleive has nothing to do with implicit >>> null. >>> >>> For Example: >>> R3----mpls----R1---R2 (2.2.2.2) >>> | | >>> (3.3.3.3) (1.1.1.1) >>> >>> MPLS is not enabled on the link between R1 & R2 & OSPF is the configured >>> IGP. R1 learns about 2.2.2.2 via OSPF >>> >>> R1#sh ip route ospf >>> 2.0.0.0/32 is subnetted, 1 subnets >>> O 2.2.2.2 [110/11] via 12.0.0.2, 00:20:44, FastEthernet0/0 >>> 3.0.0.0/32 is subnetted, 1 subnets >>> O 3.3.3.3 [110/11] via 13.0.0.3, 00:20:13, FastEthernet0/1 >>> Although MPLS is not enabled between R1 & R2, however, R1 still >>> genarates & advertises a label to R3 (100 in this case). >>> >>> R1#sh mpls forwarding-table >>> Local Outgoing Prefix Bytes tag Outgoing Next Hop >>> tag tag or VC or Tunnel Id switched interface >>> 100 Untagged 2.2.2.2/32 0 Fa0/0 12.0.0.2 >>> 101 Pop tag 3.3.3.3/32 0 Fa0/1 13.0.0.3 >>> R1 advertises this to R3 & R3 uses 100 as otugoing label: >>> R3#sh mpls forwarding-table >>> Local Outgoing Prefix Bytes tag Outgoing Next Hop >>> tag tag or VC or Tunnel Id switched interface >>> 300 100 2.2.2.2/32 0 Fa0/0 13.0.0.1 >>> 301 Pop tag 1.1.1.1/32 0 Fa0/0 13.0.0.1 >>> So the question remains, is there a scenario in IPv4 or VPNv4 when an >>> EDGE router will advertise an Implicit label aprt for connected & >>> aggregated routes? >>> >>> Thank You. >>> *From:* Nicola Arnoldi <[email protected]> >>> *To:* Narendra Naukwal <[email protected]> >>> *Cc:* "[email protected]" <[email protected]> >>> *Sent:* Sunday, 7 April 2013 7:10 PM >>> *Subject:* Re: [OSL | CCIE_RS] MPLS - PHP >>> >>> It is used as well for every route the Edge LSR learns from a PE to CE >>> routing protocol. No MPLS=PHP. >>> >>> >>> On Sun, Apr 7, 2013 at 8:16 AM, Narendra Naukwal <[email protected] >>> > wrote: >>> >>> Experts, >>> >>> Is there a scenario wherein an Edge LSR signals an Implicit Null label >>> to its directly connected Upstream neighbor for a subnet other which is not >>> Connected or Summarized on the Edge LSR? >>> >>> Thank You. >>> Naren >>> _______________________________________________ >>> For more information regarding industry leading CCIE Lab training, >>> please visit http://www.ipexpert.com/ >>> >>> Are you a CCNP or CCIE and looking for a job? Check out >>> http://www.platinumplacement.com/ >>> >>> http://onlinestudylist.com/mailman/listinfo/ccie_rs >>> >>> >>> >>> >>> >> > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
