How to sniff passwords through Cain and Abel
In this tutorial find out how to sniff passwords and capture packets using Cain and Abel software

OSPF Notes Part 2

Example OSPF packet capture
Cisco OSPF will load balance over up to four equal-cost links; configurable up to six.

Designated Routers
Neighbors on a broadcast segment elect a designated router (DR) and backup designated router
(BDR), which peer with all other routers on the segment. All non-designated routers peer only with the DR and BDR.

Multicast destinations:
224.0.0.5 - All OSPF routers
224.0.0.6 - All designated OSPF routers (DR and BDR only)
DRs are chosen based on priority (0 - 255). 1 is default; routers with 0 priority will never be elected. Priority ties are broken by choosing the higher router ID.

DRs are elected on point-to-point Ethernet links even though this is unnecessary (Ethernet is always seen as a broadcast medium). Interfaces can be configured to operate in point-to-point mode to prevent this.
(B)DRs are not preempted. New election will take place only when a current (B)DR goes offline or its OSPF process is administratively restarted.

Areas
All routers in an area maintain an identical topological database.
Areas are defined to logically segment a network and reduce routing table size and complexity.
All areas connect to area 0 (the backbone area).

Router types:
Backbone routers - Routers in area 0
Area Border Routers (ABRs) - Routers in multiple areas
Autonomous System Boundary Routers (ASBR) - Routers which redistribute information
from another AS
Internal - Routers which have all interfaces in a single area
Routers can fill multiple roles

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OSPF Notes Part 1
Link-state routing protocols utilize more internal resources in favor of reducing bandwidth consumption.
All OSPF routers in an area share the same Link State Database (LSDB).
Link State Advertisements (LSAs) are flooded to all neighboring routers.

OSPF tables:
Neighbor table
Topology database
Routing table

Forming adjacencies
Routers multicast hellos to 224.0.0.5 every 10 seconds on a broadcast link and every 30 seconds on a nonbroadcast link.
Once hellos are exchanged, neighboring routers add one another to their neighbor tables.

Contents of a hello packet:
Router ID - 32-bit unique number (IP address)
Hello/dead intervals - Timers
Neighbor list - List of neighboring router IDs
Area ID
Priority - Used in electing the DR and BDR
DR and BDR
Authentication (if enabled)
Stub Area Flag - On if this is a stub area

Neighbor states:
Down
Attempt - Used for manually configured neighbors on an NBMA link; unicast hellos sent to
neighbor from which hellos have stopped being received
Init - Hello packet received from neighbor, but without the recipient's router ID
2-Way - Bi-directional communication has been established
Exstart - The DR and BDR have been elected, link-state exchange starting
Exchange - Exchange of database descriptor (DBD) packets
Loading - Exchange of link-state information
Full - Full adjacency established

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