03-01-2010 01:06 AM
Here is a scenrio,
(1.1.1.0)CE1-PE1-P-PE2-CE2(2.2.2.0)
P router has no customer routes in its routing table, since it is not participating in iBGP.. thats perfect....
but P routers are meant to label switch packets between CE-1 & CE-2 through PE1 & PE2.. but i cannot see any labels for customer routes in P LFIB:
P#sh mpls for
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Pop tag 10.10.10.11/32 6703 Se0/1 point2point
17 Pop tag 10.10.10.10/32 2140 Se0/0 point2point
03-01-2010 01:59 AM
Hi Mukarramjahraheel
You are right . P will not participating in iBGP. He is not aware of any Customer router of BGP VPNv4 route..
P Router know only internal IGP. Please go through the below points.
The JOB of Core router is to propogate the route As Fast As Possible without delay.
Don't Get confuse in MPLS . MPLS is used for only Fast switching . Whouth MPLS also you can RUN VRF kown as VRF - Lite , BGP - AF & use CEF for fast switching.
Before Going Further Please check you Design = Whether You want to Create Full Mesh IBGP or Go With BGP Route Reflector.
Communication from CE to PE
PE routers translate into VPN-V4 route
Assigns an RD, SOO (if configured) and RT based on configuration
Re-writes Next-Hop attribute (to PE loopback ) -- When PE Re-Write the Next HOP , That next hop will IBGP VPNv4 Neighbore PE and that is reachable through internal IGP. MPLS work only for Internal IGP to forward the packet AFAP without delay .
Assigns a label based on VRF and/or interface
Sends MP-BGP update to all PE neighbors
Receiving PE routers translate to IPv4
Insert the route into the VRF identified by the RT
attribute (based on PE configuration)
The label associated to the VPN-V4 address will be set on
packets forwarded towards the destination
03-01-2010 02:07 AM
Hi,
thanks for ur reply......
to summarize, P will only have Labels in LFIB for label switching of traffic between the PEs, P will only have routes to PEs and Ps.. ?/
Regards
MukarraM
03-01-2010 02:10 AM
"Don't Get confuse in MPLS . MPLS is used for only Fast switching . Whouth MPLS also you can RUN VRF kown as VRF - Lite , BGP - AF & use CEF for fast switching."
in case MPLS is not configured, P routers will have to participate in routing between CEs and multiple contexts of IGP will be required to seperate their VPNs and overlapping address space..
MukarraM
03-01-2010 02:21 AM
Yes , I just told the example to understand the Role of P router.
03-01-2010 02:30 AM
Hi,
thanks for ur reply......
to summarize, P will only have Labels in LFIB for label switching of traffic between the PEs, P will only have routes to PEs and Ps.. ?/
Regards
MukarraM
03-01-2010 08:03 AM
If you perform Summarization at P router then it Break the LSP .
And then P router will not use the existing Label . He will assign new label.
For Example : If PE router is assign the label 50 & the same announce to all LDP neighbore then all
Other neighbore will work on same network but when P router summarlize that route then it is asume as a new network , So it will assign New Label for that Network. And fro Reverse traffic router will perform IP lookup for same & the Forward towards orignal network.
But in Cell Mode it can create issue , So while Deploying be carefully !!!
Regards
Chetan Kumar
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