BGP ( Boarder Gateway Protocol )

AS - Sharing similar routing policies and in single administrative domain.
AS number -  1 - 65535 ( 2 Byte) 
There is  4 byte AS number .
Reserved  64512 - 65535 for  private use.


Single Homed  - Only one exit point to outside.(only one ISP )


BGP message types


1.Open
2.Keeplive
3.Update
4.Notification


Path Attributes 


1. Well known mandatory 
   1.Origin
   2.AS_Path
   3.Next_Hop
2. Well known optional 
   1.Local_preference
   2. Atomic_aggregate
   3.Aggregator
3. Optional transitive
   1.Community
4. Optional non-transitive
   1.Muliti_exit_disc
   2.Originator_id (CISCO)
   3.Cluster list (CISCO)

OSPF

Open Shortest Path First (RFC : 2328 )


OSPF States :

1. Down  : No hello packets received , send the hello packet with its own router id.
2. Init : Hello received without routers id.
3.Two way 
4.Ex-start
5.Exchange
6.Loading
7.Full adjacency

OSPF Packet types :


 1.Hello
 2.Database description (DBD)
 3.Link state request (LSR)
 4.Link state update (LSU)
 5.Link state acknowledgement (LSAck)


Used Dijkstra algorithm to calculate shortest path


Link - Interface on the OSPF router

Link State :- IP address / mask of the interface (Link)
                   Metric (cost) of the link
                   Routers connected to that link
                   Type of the network connected to.

Link state database - All the link states will be keep in LSD.

OSPF Steps

• Flooding link state information
• Making a topological table 
• Shortest path first , using Dijkstra Algorithm. This will rearrange the topology.
• From that shortest path tree will make .Router itself as the root.
• Using these information will create routing table.

LSA - Types 

1.Router link entry - Router . In area only
2.Network link entry - DR
3 & 4. Summary link entry - ABR 
5. Autonomous system external link entry - ASBR


Hello packets will multicast to the address 224.0.0.5. 


OSPF Area Types :

• Backbone area
• Standard area
• Stub area
• Totally stubby area
• Not so stubby area (NSSA)

Link 1
Link 2

OSPF network types:

•  Point to point 
•  Broadcast 
• Non Broadcast
• Non Broadcast multi access 
• Point to multi point 

LINK 1

EIGRP (ENHANCED INTERIOR GATEWAY ROUTING PROTOCOL)

EIGRP is the Cisco proprietary protocol 

Metric = Bandwidth + delay  (32 bit for the metric )

Bandwidth = (10000000/bandwidth) * 256

Delay = ( delay /10 ) * 256

Metrics are follows :- 
1.Bandwidth
2.Delay
3.Reliability
4.Load

Its is a classless routing protocol . Hop count is 255 (default is 100).

Routing table metric = Slowest bandwidth + sum of all delays 

Bandwidth :- 
T1 = 1554K
FE = 10000K
E = 10000K

Delay :-
T1 =20000mS
FE =100mS
E = 1000mS

In EIGRP outside routes (from distributed routes ) are tagged as external routes.
Automatic redistribution between EIGRP and IGRP if its both are same AS.

Metric = K1 * bandwidth + (K2 * bandwidth) / (256 -Load) + (k3 * delay ) + (k5/( reliability * k4)


 
Q. What is the Metric ( cost ) for 192.168.72.0/24 from ROUTER B.

Cost = slowest bandwidth + sum of delays.

= 1,657,856 +
      512,000 +
          2560 
___________
    2172416  

If you look at the routing table you will able to see




EIGRP will do the unequal cost load balancing .

EIGRP TABLES
1.Neighbor  Table :- Keeps all adjacent routers (neighbors) . Protocol wise separate table is there . 
ROUTER# show ip eigrp neighbors

2.Topology Table :- Keeps all the learned routes .Protocol wise separate table is there .(from distribution )
ROUTER# show ip eigrp topology

3.Routing Table :- Keeps the best routes from topology table to all destination.
ROUTER# show ip route


Successor : Easiest route to one destination. Keep in routing table. One or more successor may have to one destination.

Feasible Successor : Backup route for the successor. Keep in topology table.May have one or more FS to same destination.


Key Technologies of EIGRP :

Neighbor discover and recovery
Reliable Transport Protocol
Dual finite state machine
protocol specific modules

EIGRP Packet types :

1.Hello
2.Acknowledgement
3.Update
4.Query
5.Reply

 By default in EIGRP hold time is three times of hello interval.

Less than T1 (1554K) =  Hello interval 5 secs  Hold time = 15 secs

Greater T1 (1554K) =  Hello interval 60 secs  Hold time = 180 secs

If required we can modify the hello interval and hold time.
To form neighbors not required to match  hello and hold time at both ends.
In OSPF to make an neighbor need to match the hello and hold time .




There are three conditions needs to met then only neighborship will be established.

1. Hello or Ack received
2. AS numbers match
3. Identical metrics ( K Values )

SHORT FORMS USED IN MAIL

SOW- Statements of work
RMA - Risk Management Association
RFO - Reason For Outage
MoM - Minutes of Meeting
PFA - Please Find the Attachment
FYI - For your information
FYA - For your attention 
EOD - End of the Day
ETA - Estimated Time of Arrival
FE - Feild Engineer
RCA - Root Cause Analysis
ETR - Expected time of return
HA - High Availability
SLA - Service Level Agreement

Ethernet Switching

Layer 3 topology

Layer 2 Ether Cahanel

Router on Stick

Port Security

To configure trunking and assign vlan numbers.


Interface Types

L2  Switch ports

• Access
• Trunk
• Dynamic
• Tunnel

L3 ports

• switched virtual interface ( SVI )
• Native Routed interface

L2 and L3 VPN

1. What is the difference between L2 VPN and L3 VPN.

    L2 VPN 

•        ISP devices forward the frames according to L2 information.    (DLCI,MAC,VLAN ID )
•        Enterprise stays in control of L3 policies ( Routing , Q0S)

        
  L3 VPN

•        ISP devices will forward the packets according to L3 information.( IP       addresses)
•        ISP involved in Customer IP routing.
•        IP specific

     

HSRP ( HOT STANDBY ROUTER PROTOCOL)

HSRP  is a cisco proprietary protcol , VRRP (Virtual Redundancy Router Protocol) is the open standard used for redundancy RFC 3768.

HSRP process have 6 states .

1. Initial

  This will happens in only two time , once the config change done and after router reboot.

2. Learn

3. Listen

4. Speak

5.Stand by

6. Active 

Config :

R1(config-if)# standby 100 ip 192.168.100.1
R1(config-if)# standby 100 priority 100
R1(config-if)# standby 100 track fa 0/0/1     /* This will track the interface , if its down decrement the priority  *|
R1(config-if)# standby 100 preempt    /* This will ensure highest priority router is the active one. *\