EIGRP REVISION  

Friday, November 14, 2008

the points are scattered so please dont mind

* Eigrp may be termed as enhanced igrp . defined as hybrid with both distance vector and link state .. but to be precise may be termed as advance distance vector routing protocol out there

* It works on on local link multicast exchange 224.0.0.10

* Neighbor process or discovery is done with the help of exchange of hello exchage . neighbours are alive till hellos are exchanged

* For multicast exchange , all of the interfaces must be of multicast capable .. this includes atm / frame - relay concepts

* The neighbor discovery process is done via hello packets that are exchanged via multicast

* Eigrp offers multiprotocol support ip , ipx , appletalk

* Eigrp provides RTP RELIABLE TRANSPORT PROTOCOL . through this packets can be exchanged via unicast / multicast

* The point to remember is that Hello packets are not needed to be reliable

On to the algorithm and routing proc

* DUAL - diffusing update algorithm . responsible for processing , installing and maintaining routes

* Also has to offer list of routes for feasible successors and successors via next hop

* If no feasible successor is present , or route goes down Recomputation is done

* Recomputation is processor intensive and uses dual to see the neig relationships again

* Table in eigrp include NEIGHBOR TABLE , TOPOLOGY TABLE , ROUTING TABLE

* Neighbor table contains adjacent neighbors , how neighbors has been discovered , interfaces , hold time , neighbor id , transmissions

* Topology table . this is done by the protocol module .. ie if we are running eigrp under ip , the table will be populated by ip protocol

* This is the backbone . it contains all destination routes advertised by neigh , metrics , perfixed , list of neigh , and for each route there will be metric which is advertised

* The route with best metric will be forewarded to the routing table . it is termed as successor ie primary path

* Feasible successor more or less like a back up path . one path can have multiple feasible successors . if successor goes down it will replace by fs and for replacement no recomputation is necessary

NEIGHBOR OPTIONS IN EIGRP

* Neighbor table is dynamically built as it receives hellos from different neighbors

* SHOW IP EIGRP NEIGH can be used for viewing neigh , addr , int , neigh

* NEIGHBOR COMMAND is to statically specify neighbors and also should be specified with the interface with which it can be reached . this is used to establish unicast routing

neig 100.0.0.10 fa0/0

* The results can be seen by the SHOW RUN , SHOW IP PROTOCOLS

* SHOW IP EIGRP NEIGHBORS will not list it because you need to have neighbor command done on both neig routers

* PASSIVE INTERFACE cannot be done on eigrp as it uses multicast hellos and hellos are to be sent in order to have a neigbor relation ship

* If we are asked to configure a passive interface in eigrp a simple way to do is to configure DISTRIBUTE LISTS .

* Create an access-list denying all traffic and place in the router process with the help of distribute list

ACCESS-LIST 30 DENY ANY

DISTRIBUTE-LIST 30 OUT


MORE INTO SIMPLE CONFIS AND METRICS

* METRICS OR K VALUES bandwidth , load ,delay , reiablilty , mtu .

* SIA ERROR stuck in active . this is where when mentioned no fs can be found for the topology table . the problem is that it wont have any timeout period and sia packet goes on and on till it gets a yes or no reply from neigh . if the router is busy to respond to this sia packet more time will be taken for recomputation

* Three simple steps

enabling routing protocol

defining as number

giving network command

* ROUTER EIGRP 125
NETWORK X.X.X.X
NO AUTO ------------ to turn off auto summaraisation

* SHOW IP PROTOCOLS can be used to see timers , neigh , metrics

k-values can be seen here .

* A K VALUE IS A 32 BIT NUMBER / MODIFIER .. SO IF YOU CHANGE VALUE OF K OR INCREASE A K VALUE BY ONE IT WILL AFFECT HUGELY

* metric can be best viewed with show ip route command

* K-values can be modified with the help of metric weights command

METRIC WEIGHTS ALWAYS START WITH ZER0 AND FOLLOWED BY K1 . K2 , K3 , K4 , K5

DEFAULT VALUES ARE 1 0 1 0 0

BANDWIDTH , LOAD , DELAY , RELIABILITY , MTU


these are few of the updates from me .. need to update blog ..it is lagging like hell lol smile.gif ... i will continue with the eigrp revision part ..

good luck at what ever you do and also wish me

regards
RAKESH





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