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
... i will continue with the eigrp revision part ..good luck at what ever you do and also wish me
regards
RAKESH