Properties of Reliable Delivery Service

1. Stream Orientation: Stream delivery service on destination passes to the receiver exact same sequence of bytes that the sender passes it to the source.

2. Virtual Circuit Connection: Protocol softwares on both the ends communicate by verifying that the transfer is authorized and both sides are ready. Once all details have been settled, the protocol modules inform the application programs that the connection has been established and that transfer can begin.

3. Buffered transfer : When transferring data, each application uses whatever size pieces it finds convenient, which can be as small as a single octet.

4. Unstructured stream : Application programs using the stream service must understand stream content and agree on stream format before they initiate a connection.

5. Full duplex connection : A full duplex connection consists of two independent streams flowing in opposite directions, with no apparent interaction. The advantage of a full duplex connection is that the underlying protocol software can send control information for one stream back to the source in datagrams carrying data in the opposite direction. Such piggybacking reduces network traffic.

What is difference between Limited Broadcast address and Directed Broadcast address

We all know broadcast address . It is the address used to address all in the same LAN ( Local Area network).

In broadcast we have two types : Limited broadcast and Directed broadcast. What is the difference between the directed broadcast and the Limited broadcast ?

Limited broadcast is the broadcast limited to a single LAN and which is to be received by all. It is sent to reserved Class E , IP address 255.255.255.255. The destination MAC address for such frames will be FF:FF:FF:FF:FF:FF.  The router simply drop the Limited broadcast address and does not forward it.


Directed Broadcast address is the local subnet broadcast address. If the subnet is 192.168.10.0 , the directed broadcast address will be 192.168.10.255 , which will be heard by all in the same subnet hosts. The router will receive such packet and process it.The  destination mac address will still be FF:FF:FF:FF:FF:FF, as it is to be received by all hosts.

DHCP packets are Limited broadcast packets and NBNS uses directed broadcast packets.

Commands to configure L3 switch for inter vlan routing

1. switch(config)# ip routing

2. switch(config)#int gi1/0/1
    switch(config-if)#switchport access vlan 2
    no shutdown


3. switch(config)#interface vlan 2
   ip address 10.1.2.1 255.255.255.0


Video: http://www.youtube.com/watch?v=BOFHo13ATZE

Default Administraive Distance Value Table

Default Distance Value Table

This table lists the administrative distance default values of the protocols that Cisco supports:

Route Source	Default Distance Values
Connected interface	0
Static route	1
Enhanced Interior Gateway Routing Protocol (EIGRP) summary route	5
External Border Gateway Protocol (BGP)	20
Internal EIGRP	90
IGRP	100
OSPF	110
Intermediate System-to-Intermediate System (IS-IS)	115
Routing Information Protocol (RIP)	120
Exterior Gateway Protocol (EGP)	140
On Demand Routing (ODR)	160
External EIGRP	170
Internal BGP	200
Unknown*	255

* If the administrative distance is 255, the router does not believe the source of that route and does not install the route in the routing table.

When you use route redi

Internet Group Management Protocol (IGMP)

How IGMP Operates 

The Internet Group Management Protocol (IGMP) is an internal protocol of
the Internet Protocol (IP) suite. IP manages multicast traffic by using
switches, multicast routers, and hosts that support IGMP. (In ProCurve’s
implementation of IGMP, a multicast router is not necessary as long as a switch
is configured to support IGMP with the querier feature enabled.) A set of hosts,
routers, and/or switches that send or receive multicast data streams to or from
the same source(s) is termed a multicast group, and all devices in the group
use the same multicast group address.

Message Types
The multicast group running version 2 of IGMP uses three fundamental types
of messages to communicate:
■ Query: A message sent from the querier (multicast router or switch)
asking for a response from each host belonging to the multicast group. If
a multicast router supporting IGMP is not present, then the switch must
assume this function in order to elicit group membership information 4-12
Multimedia Traffic Control with IP Multicast (IGMP)

■ Report (Join): A message sent by a host to the querier to indicate that
the host wants to be or is a member of a given group indicated in the report
message.
■ Leave Group: A message sent by a host to the querier to indicate that the
host has ceased to be a member of a specific multicast group.

IGMP Querying/Snooping

A Layer 2 switch supporting IGMP Snooping can passively snoop on IGMP Query, Report, and Leave (IGMP version 2) packets transferred between IP Multicast routers/switches and IP Multicast hosts to determine the IP Multicast group membership. IGMP snooping checks IGMP packets passing through the network, picks out the group registration, and configures Multicasting accordingly.

Without IGMP Querying/Snooping, Multicast traffic is treated in the same manner as a Broadcast transmission, which forwards packets to all ports on the network. With IGMP Querying/Snooping, Multicast traffic is only forwarded to ports that are members of that Multicast group. IGMP Snooping generates no additional network traffic, which significantly reduces the Multicast traffic passing through your switch.

For further info :

http://ezinearticles.com/?Multicast-IGMP-and-PIM&id=3711762

Border Gateway Protocol

Introduction

BGP is a standardized exterior gateway protocol (EGP), as opposed to RIP,  OSPF, and EIGRP which are interior gateway protocols (IGP’s). BGP  Version 4 (BGPv4) is the current standard deployment. 

BGP is considered a “Path Vector” routing protocol. BGP was not built to  route within an Autonomous System (AS), but rather to route between AS’s.  BGP maintains a separate routing table based on shortest AS Path and various other attributes, as opposed to IGP metrics like distance or cost. 

BGP is the routing protocol of choice on the Internet. Essentially, the Internet is a collection of interconnected Autonomous Systems. 

BGP Autonomous Systems are assigned an Autonomous System Number  (ASN), which is a 16-bit number ranging from 1 – 65535. A specific subset of this range, 64512 – 65535, has been reserved for private (or internal) use. 

BGP utilizes TCP for reliable transfer of its packets, on port 179.

BGP Peers (Neighbors) 

For BGP to function, BGP routers (called speakers) must form neighbor  relationships (called peers). 

There are two types of BGP neighbor relationships: 

• iBGP Peers – BGP neighbors within the same autonomous system. 

• eBGP Peers – BGP neighbors connecting separate autonomous systems. 

 Note: Do not confuse an IGP, such as OSPF, with iBGP! 

By default, BGP assumes that eBGP peers are a maximum of one hop away. This restriction can be bypassed using the ebgp-multihop option with the neighbor command.

The Administrative Distance for routes learned outside the Autonomous System (eBGP routes) is 20, while the AD for iBGP and locally-originated routes is 200.

BGP Peers Messages 

BGP forms its peer relationships through a series of messages. 

1. First, an OPEN message is sent between peers to initiate the session. The OPEN message contains several parameters:

BGP Version – must be the same between BGP peers Local AS Number BGP Router ID

2. KEEPALIVE messages are sent periodically (every 60 seconds by default) to ensure that the remote peer is still available. If a router does not receive a KEEPALIVE from a peer for a Hold-time period (by default, 180 seconds), the router declares that peer dead. 

3. UPDATE messages are used to exchange routes between peers. 

4. Finally, NOTIFICATION messages are sent when there is a fatal error condition. If a NOTIFICATION message is sent, the BGP peer session is torn down and reset.

Configuring Neighbors:
RouterB(config)# router bgp 100
RouterB(config-router)# neighbor remote-as
RouterB(config-router)# neighbor 172.16.1.2 remote-as 900

For stability purposes, the source interface used to generate updates to a
particular neighbor can be specified:

RouterB(config)# router bgp 100
RouterB(config-router)# neighbor 172.16.1.2 update-source lo0

RouterC must then point to RouterB’s loopback (assume the address is
1.1.1.1/24) in its neighbor statement:

RouterC(config)# router bgp 900
RouterC(config-router)# neighbor 1.1.1.1 remote-as 100

RouterC must have a route to RouterB’s loopback in its routing table.

Remember though: by default, BGP assumes that external peers are exactly
one hop away. Using the loopback as a source interface puts RouterB two
hops away from RouterC. Thus, the ebgp-multihop feature must be enabled:

RouterC(config)# router bgp 900
RouterC(config-router)# neighbor 1.1.1.1 ebgp-multihop 2

The 2 indicates the number of hops to the eBGP peer. If left blank, the
default is 255.

To authenticate updates between two BGP peers:

RouterB(config)# router bgp 100
RouterB(config-router)# neighbor 172.16.1.2 password CISCO

Further Info :
http://www.routeralley.com/ra/docs/bgp.pdf

IS-IS Commands

IS-IS status

„Show clns : Information about the CLNS network

„Show clns protocol : Lists the protocol-specific information

„Show clns is-neighbor : IS-IS neighbors

„Show clns neighbor : Both ES and IS information

„Show isis database : LSDB

„Show isis topology : ISIS least-cost paths to destinationIS-IS command

„

Router#conf t

Router(config)#router isis      : enable IS-IS

Router(config-router)# net [network entity title]

Router(config-router)#net  49.0401.2101.8302.8174.00

Router(config-router)# is-type  [level-1/level-1-2/level-2-only]

Router(config-router)#

exit

„

Router(config)#interface[interface type] [interface number]

Router(config-if)#ip router isis

Router(config-if)#isis circuit-type[level-1/level-1-2/level-2-only]

: need to repeat for all interfaces that need to run IS-IS

Router#show ip route isis     : check routing table