FIB, LIB and LFIB

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Sep 19th, 2007
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Guys can someone please help me out as i cant get my head around MPLS terminologies......they say that FIB is derived from CEF and it sth etable which is mapping of network to lables (as in CEF its network to MAC) now LIB is mapping of lable to lable and say sthat it developed whne ldp is configured and LFIB is again network to lable maping.....so whats the difference between FIB and LFIB??? does LSR router contains all th etables (all three of it) guys plz help me out as i m vvv confused??? regards

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ratheeshrg Thu, 09/20/2007 - 02:50
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Hi,

Take it this way

LIB--- whenever a labelled packet comes this table will be refered


FIB---whenever a nonlabelled packet comes this table will be refered


LFIB---Any route in the LFIB will also be in the LIB, but not the other way around. The LFIB is a subset of the LIB, based on SPF algorithm calculation.


Cheers

Ratheesh Nair


jayjorda Thu, 09/20/2007 - 05:39
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Taken a little furhter:


LIB is control plane - built by LDP, RSVP, etc based on entries in the RIB (routing information base - also control plane, built by OSPF, connected, static, etc). Maps all the entries in the RIB to an appropriate label


LFIB is forwarding plane. These are the entries that are used for forwarding lookup. Derived from the FIB (forwarding information base, which is derived from RIB).


FIB, along with the adjacency table is what comprises CEF.


unlabeled IP packets are identified by the protocol ID\Ethertype value in the layer 2 header, which would be 0x0800 and would be processed by the FIB


labeled packets are identified by the protocol ID\Ethertype value in the layer 2 header, which would be 0x8847 for mpls unicast and 0x8848 for mpls multicast and would be processed by the LFIB



Harold Ritter Sun, 09/23/2007 - 16:26
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Jay,


Just one precision, labels learnt via RSVP are not stored in the lib.


Regards,

jayjorda Mon, 09/24/2007 - 05:33
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Harold,


Thanks for the correction.



Jay


raghavbhargava Wed, 09/26/2007 - 00:33
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HI ,


I just read ur comment.can u please tell me that in case of RSVP where are the labels stored if not in LIB. Is it the LFIB.and How??


Regards

Raghav

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