There are some advantages dividing routers into different OSPF areas which are:
1. Router processing is less because of smaller routing tables
2. Limit LSA traffic, more bandwidth effecient
OSPF has an AD of 110 and uses costs as metrics. The formula for OSPF costs formula are (100,000,000/BW in bps), where the path with lower costs is preferred. To change cost use the command:
(config-if)#bandwidth
To change the cost by changing the reference use the command:
(config)#router ospf
(config-router)#auto-cost reference-bandwidth
There are several reasons why OSPF is better than RIP such as:
1. OSPF metric is more accurate about the actual distance to a remote network (based on speed), where RIP uses hop counts only.
2. OSPF networks are always reachable, compared to RIP's maximum hop count of 15, to combat loop infinity.
3. OSPF has VLSM, whereas RIP not. This is an advantange because of the more efficient utilization of IP addresses.
4. OSPF has better network bandwidth utilization (less broadcasts and does not update the full routing table)
5. OSPF converges more quickly
OSPF adjacency process has several states:
- Down : No hellos received from that neighbor
- Attempt : Hello packets are sent to neighbors, which are seen only in NBMA networks, since they configure neighbors
- Init : First Hello packet has been received from the neighbor, but does not have the RID in it
- 2-Way : Each router on the end of the link has received a Hello packet with each own RID meaning that the routers are sycnchronized.
- Exstart : Exchange process of the link state database information starting with the highest OSPF RID router
- Exchange : Database Descriptor (DBD) packets which contain a description of the link state database are exchanged.
- Loading : Routers are sending Link State Requests (LSR) packets to the potential neighbor
- Full : Router databases are synchronized and the adjecency is finally formed.
All DROTHERS will be in the 2 way state as the final state. Only the DR and BDR will have a full state adjecency to all the other routers, because a DROTHER cannot send an LSA to another DROTHER so therefore not necessary for DROTHER to go to this state.
-- 4 January 2010 --
1. Router processing is less because of smaller routing tables
2. Limit LSA traffic, more bandwidth effecient
OSPF has an AD of 110 and uses costs as metrics. The formula for OSPF costs formula are (100,000,000/BW in bps), where the path with lower costs is preferred. To change cost use the command:
(config-if)#bandwidth
To change the cost by changing the reference use the command:
(config)#router ospf
(config-router)#auto-cost reference-bandwidth
There are several reasons why OSPF is better than RIP such as:
1. OSPF metric is more accurate about the actual distance to a remote network (based on speed), where RIP uses hop counts only.
2. OSPF networks are always reachable, compared to RIP's maximum hop count of 15, to combat loop infinity.
3. OSPF has VLSM, whereas RIP not. This is an advantange because of the more efficient utilization of IP addresses.
4. OSPF has better network bandwidth utilization (less broadcasts and does not update the full routing table)
5. OSPF converges more quickly
OSPF adjacency process has several states:
- Down : No hellos received from that neighbor
- Attempt : Hello packets are sent to neighbors, which are seen only in NBMA networks, since they configure neighbors
- Init : First Hello packet has been received from the neighbor, but does not have the RID in it
- 2-Way : Each router on the end of the link has received a Hello packet with each own RID meaning that the routers are sycnchronized.
- Exstart : Exchange process of the link state database information starting with the highest OSPF RID router
- Exchange : Database Descriptor (DBD) packets which contain a description of the link state database are exchanged.
- Loading : Routers are sending Link State Requests (LSR) packets to the potential neighbor
- Full : Router databases are synchronized and the adjecency is finally formed.
All DROTHERS will be in the 2 way state as the final state. Only the DR and BDR will have a full state adjecency to all the other routers, because a DROTHER cannot send an LSA to another DROTHER so therefore not necessary for DROTHER to go to this state.
-- 4 January 2010 --
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