Network Layer Lesson-3
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Network Layer (Static Routing, Dynamic routing)

Network Layer :Static Routing, Dynamic routing

Network Layer :Static Routing, Dynamic routing
Network Layer (CCNA) Lesson-3

CCNA

Network Layer (Static, Dynamic Routing) :-

Type of Routing:-

  1. Static Routing :- which is process manually entering routes to remote destination in your routing table

serial two router connection

Creating Static Route

(IP Route) (Destination network) (Destination mask) (Next hop IP OR exit interface) (admin distance)

Routing controls: - the lower administrator distance is better

The default of administrative distance:-

  1. Connected route have AD (administrative distance) = 0

Static router have AD = 1

  1. RIP (Route Information Protocol) :- have AD = 120 (dynamic Router Protocol) :- defined a range of addresses if an IP exist in that range on the router the interface the IP is included in router protocol
  2. EIGRP(Enhanced internal Gateway Routing Protocol) have AD = 90 (dynamic route)
  3. OSPF (Open Shortest Path First) :- have AD =110 (Dynamic Route)

Trace route: - is a function where you can get the IP’s between one source and one destination by doing a trace route to it and every router that the traces threw will send you back its IP address

  1. Dynamic routing :- when routers talk to each other and automatically share routers to remote destination or remoter networks

There are two type of dynamic routing protocol:-

  • distance vector routing protocol: - the only pure distance vector routing protocol
  • Routing information protocol (RIP)

Features:-

Send whole routing table every set interval

Send the routing update to 255.255.255.255 (not good thing)

Use HOP count as metric (Measure of distance between local router and remote destination (network))

Measure of distance between local router and remote destination (network)

Network is available to router 1 within 2 HOP

Network is available to router 2 within 1 HOP

Network is available to router 3 within 0 HOP

Distance vector routing protocol have inbuilt loop prevention mechanism (throw):

  1. Maximum hot counts:- when the maximum hop count is reach the packet (kill) 15 Hop
  2. Split horizon :- if I send an update about a network outbound on an interface I will not accept an inbound update about the same network coming in on that interface
  3. Route poisoning :- you advertise down route with infinite metric, if router 3 disconnect with network it will send down for router2
  4. Router invalid timer :- the length of time that router wait till hear a router update from upstream router before declaring that network down (180 sec)
  5. Hold down timer: - when the invalid timer expire the hold down timer started, when its down it will not accept any update about that router for that length of time
  6. Poison reverse :- advertising a router back upstream with poison with infinite metric
  7. Flush time :- the time which the route is completely removed from the IP router table

Some of dynamic Route Protocols (distance vector routing protocol)

  • RIP (Route Information Protocol) :- have AD = 120 (dynamic Router Protocol) :- defined a range of addresses if an IP exist in that range on the router the interface the IP is included in router protocol
  • EIGRP(Enhanced internal Gateway Routing Protocol) have AD = 90 (dynamic route) :- advanced distance vector routing protocol

Updates are partial, bounded and non-periodic: only sent update when something in the topology changes

Uses hello for neighbor discovery and keep alive (hold time) 5 Sec

Stores all routes in topology table even multiple routes to some destination and topology table change after neighbor discovery

Best route is successor (lowest feasible distance), feasible distance is metric

Reported distance: - is feasible distance for upstream closer routers.

Feasibility condition: - route reported distance must be less than route feasible distance to be installed in topology table.

EIGRP (Enhanced internal Gateway Routing Protocol) variance:-

Enhanced internal Gateway Routing Protocol can send echo amount of traffic over multiple links if there is metric matching (called equal cost load sharing)

  • OSPF (Open Shortest Path First) :- have AD =110 (Dynamic Route) :- not a distance vector routing protocol, its state routing protocol

Each router describe itself in packet which is (link state advertisement)

Link state advertisement contains:-

Router links with IP networks linked to those links, neighbors’ router and the metric to get those neighbors.

Link state advertisement is flooding by every router

Identical link state database: - built on routers, every router has link state advertisement (LSA) for other routers

When get Open Shortest Path First on a router the other routers do database synchronization to become adjacency formation (neighbor ship formation)

Neighbors stay alive throw hello messages

Open Shortest Path First routers by default have priority equal to 1, the higher priority is better for becoming designated router.

Neighbor States:-

  1. Down state :- hello received
  2. Attempt state :- neighbors must be configured manually
  3. INIT state :- hello packet received from neighbor
  4. 2 way state :- hello packet received from neighbor with local router route id bidirectional communication established
  5. Ex start state :- routers prepare for identical link state database synchronization (router with highest id becomes the master and controls database exchanges)
  6. Exchange state :- database description , link state request and link state update packets exchange
  7. Loading state :- link state request packets are sent requesting missing link state advertisement
  8. Full :- ends synchronization

Autonomous system boundary router (ASBR):- router that take us out from our network to another network

Link state advertisement (LSA) types:-

  1. Router LSA
  2. Network LSA :- produce from designated router of the network
  3. Network summary LSA :- produce by area boarder router
  4. ASBR summary LSA: - generated by area boarder router (ABRs), topological database which ABR receives from other areas are injected into the backbone area
  5. External LSA :- carry all the networks that are external to the OSPF domain

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TOPICS:  CCNA