The MPLS WG Archive

["Gopal@Cisco" <gnaganab@cisco.com>]

Sachin, PLs see iinline...

Sachin Kalra wrote:
> 
> Hi Robert:
> 
> Thanks for the reply.
> 
> > PE2 should based on the information retrived from the VPN label do
> > the
> > vrf lookup which reveals that the packet is destined to itself.
> > There is
> > no need to send it to CE11.
> 
> But shouldn't PE2 do a "NHLFE lookup" instead of "VRF lookup" when it
> gets a packet from PE1, with a label.
> 
> And if PE2 only does a NHLFE lookup then all it gets is an outgoing
> interface for the label. (In this case out iface will be the one
> connecting to CE11)

OUtgoing interface is empty for connected routes in NHLFE. Just like
this,

R3#sho tag for tag 27
Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop    
tag    tag or VC   or Tunnel Id      switched   interface              
27     Aggregate   10.10.33.0/24[V]  0                                  
R3#




> 
> Please comment.
> Thanks,
> Sachin Kalra
> 
> *********************************************************************************
> Just to be more clear, following is my VRF table at PE2. Where
> 
> 1. "192.0.5.1" is the interface on PE2 (that connects PE2 and CE11).
> 2. "192.0.5.2" is the interface on CE11 (that connects CE11 and PE2).
> 3. "192.0.25.1" is the loopback interface on CE11.
> 4. "192.0.7.1", "192.0.1.1", "192.0.19.1" are PE1, CE1 and CE2
> respectively
> 
> ======================================================
> VRF Table for VRF_A at PE2:
> 
> Destination       Subnet Mask        Next Hop      Out Iface    Bottom
> Label   Top Label
> -----------            -----------                 ------------
> ---------        ------------           ---------
> 192.0.5.0          255.255.255.0      192.0.5.1       IF0
> 31                   UNDEF
> 192.0.25.0        255.255.255.0      192.0.5.2       IF0
> 32                   UNDEF
> 192.0.1.0          255.255.255.0      192.0.7.1       IF2
> 31                   31
> 192.0.19.0        255.255.255.0      192.0.7.1      IF2
> 32                   31
> ======================================================
> 
> At 11:09 PM 1/15/03 +0100, Robert Raszuk wrote:
> 
> > Hi Sachin,
> >
> > > Because it just look at the bottom label of the packet,
> > > and as per the entries into its VRF table, PE2 just sends out the
> > packet to
> > > CE11.
> >
> > PE2 should based on the information retrived from the VPN label do
> > the
> > vrf lookup which reveals that the packet is destined to itself.
> > There is
> > no need to send it to CE11.
> >
> > R.
> >
> > > Sachin Kalra wrote:
> > >
> > > Dear MPLS Community:
> > >
> > > I would appreciate if someone can answer the following question
> > about
> > > BGP-MPLS VPNs.
> > >
> > > Lets say we have the following topology:
> > >
> > > [CE1]
> > [CE11]
> > >
> > \                                                           /
> > >          [PE1]-----------------[Rtr1]-------------------[PE2]
> > >
> > /                                                           \
> > > [CE2]
> > [CE22]
> > >
> > > 1. PE and CEs have static routes configured between each other.
> > i.e. no
> > > routing protocol running on the interfaces connecting PEs and CEs.
> > >
> > > Question. How will a packet going from CE1 and destined to
> > interface on PE2
> > > (that connects PE2 and CE11) reach its destination?
> > >
> > > The problem is that when PE2 receives a packet destined to its out
> > > interface connecting "PE2->CE11". PE2 does not know that the
> > packet is
> > > destined to itself. Because it just look at the bottom label of
> > the packet,
> > > and as per the entries into its VRF table, PE2 just sends out the
> > packet to
> > > CE11.
> > >
> > > Is this the correct behavior?
> > >
> > > I appreciate your response.
> > > Thanks,
> > > Sachin Kalra
> 
> ===========================================================
> Sachin Kalra
> Modeling Engineer
> OPNET Technologies, Inc.
> (240)-497-3000 x2796
> ===========================================================
> Register for OPNET's Online Technology Workshops
> (http://www.opnet.com/TechWorkshops/)
> ===========================================================

-- 
Gopal(www-tac/~gnaganab),CCIE#6209,1.408.525.9922,RP-TAC,9:00AM-5:00PM(PST)
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