[CCNA2] - OSPF Challenge
Manipulating OSPF Cost in 3 different ways on the given topology. The answer to the question can be given using a lot of high level solutions like route-maps, distance etc. but you have to use only CCNA2 level knowledge to accomplish this. enjoy :).
Beginners MPLS FAQ
Q: What is Multi−Protocol Label Switching (MPLS)?
A: MPLS is a packet−forwarding technology which uses labels to make data forwarding decisions. With MPLS, the Layer 3 header analysis is done just once (when the packet enters the MPLS domain). Label inspection drives subsequent packet forwarding. MPLS provides the following beneficial applications: Virtual Private Networking (VPN), Traffic Engineering (TE), Quality of Service (QoS) and ATM over MPLS (AToM). Additionally, it decreases the forwarding overhead on the core routers. MPLS technologies are applicable to any network layer protocol.
Q: What is a Forwarding Equivalence Class (FEC)?
A: FEC is a group of IP packets which are forwarded in the same manner, over the same path, and with the same forwarding treatment. An FEC might correspond to a destination IP subnet, but it also might correspond to any traffic class that the Edge−LSR considers significant. For example, all traffic with a certain value of IP precedence might constitute a FEC.
Q: What is a LSR?
A: An Label Switch Router is a router that can support MPLS
Q: What is LDP?
A: Label Distribution Protocol (LDP) is a standard protocol between MPLS-enabled routers to negotiate the labels (addresses) used to forward packets. LDP provides a standard methodology for hop-by-hop, or dynamic label, distribution in an MPLS network by assigning labels to routes that have been chosen by the underlying Interior Gateway Protocol (IGP) routing protocols.
Q: What is RIB/FIB?
A: Routin Information Base(RIB) is the Table which is build up by Routing Protocols or static Routes. It could have the same entry for reaching one network with the corresponding metrics. The Forwarding Information Base(FIB) has only one entry per network, the FIB is gerated (as a subset) by the RIB, the FIB tuples are unique.
Q: What is LIB/LFIB?
A: The Label Forwarding Information Base (LFIB) is derived from the Label Information Base (LIB), it is a subset of the LIB. Also the LFIB contains no IP information whereas the LIB does hold IP information. Cisco says the LFIB is generated when the actual shortest path to a destination is chosen. Hence, in the LFIB there will be one label pair for a destination (or FEC), whereas the LIB holds all possible paths to the destination.
Q: What is LSP?
A: Path along which labeled packets are forwarded. Packets forwarded using any label are forwarded along the same path as other packets using the same label.
Q: What is PHP?
A: A process by which the peer immediately upstream of the egress LSR is asked to pop a label prior to forwarding the packet to the egress LSR. Using LDP, this is done by assigning the special value of the implicit Null label. This allows the egress to push the work of popping the label to its upstream neighbor, possibly allowing for a more optimal processing of the remaining packet. Note that this can be done because once the label has been used to determine the next-hop information for the last hop, the label is no longer useful. Using PHP is helpful because it allows the packet to be treated as an unlabeled packet by the last hop. Using PHP, it is possible to implement an “LSR” that never uses labels.
More to come
Basic MPLS acronyms
Here is a little list I’ve made with some acronyms used in MPLS terminology that might help you understand what do they mean when you see them:
MPLS - Multi-Protocol Label Switching
LSR - Label Switch Router
LDP - Label Distribution Protocol
FIB - Forwarding Information Base
LFIB - Label Forwarding Information Base
LSP - Label Switched Path
FEC - Forwarding Equivalence Class
PHP - Penultimate hop poping
VPI - Virtual Path Identifier
VCI - Cirtual Circuit Identifier
VC - Virtual Circuit
TDP - Tagged Distribution Protocol
CEF - Cisco Exprese Forwarding
LC-ATM - Label Control ATM
SOO - Source Of Origin
Later on will be an explanation of each feature
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