Powerpoint of Trouble shooting techniques from scott morris  

Thursday, February 26, 2009

I always like the powerpoint way ... i love it ... i was going through the internetwork expert blog today and found excellent article by mr.scott morris on some general trouble shooting techniques that can drive you insane if not observed ... i have made a power point ... its publicly available in their site if you want to visit it .. you can always do it on


here is the link



Friday, February 20, 2009

Video 3 of the ospf lab has been released and it is based on ospf virtual link concept..... please feel free to see the topology and also some of the important points in the word doc which is also available ...

you can download the video here ..






In order to make sure that spf is executed properly , area 0
is used as reference point for all other areas in the network

Hence all other areas must have a direct adjacency to area 0

So, the discontiguos area should be connceted to area 0 thorugh
any transit area attached to it , through virtual links

Hence , after the configuration the entire set of ospf
databases will be synced and full connectivity will be esatblished


To define ospf virtual link, use the area virtual-link command in

Usage Guidelines :

In ospf , all areas must be connected to a backbone router .If
the connection to backbone is lost it can be repaired using

For a virtual link to be properly configured , each
virtual link neighbor must include transit area id and the
corresponding virtual link neighbor router id

Video 3 Released ;)  

Thursday, February 19, 2009

video 3 has been done and it is on eigrp convegence timers over frame relay ... a word document has also been attached for the reference of topology and points ...

you can download them at


lab 2 video ready for download...  

Tuesday, February 17, 2009

Hello ... the lab2 video of ospf point-to-point has been done and been uploaded ... please feel free download it and also the word doc ..


All of the basic ip addressing and frame relay mappings are done and are not included in the video ... the word doc presents you with the topology and some of the important points


Thought and i will give it for free  

I dint wanted to sell the videos even for 5$ but i thought of buying few routers and switches for the switching labs ... but its against my self .. so decided that i would be giving my work to any one who requires for free ... i got 4 paid requests from 4 of the friends .. but i would returning the money back to them tonight .... hence from here on please feel free to download labs and word docs for free .. and if you like you and you have something to throw you can always consider me ... ;)

Also looking for some good team members who can study with me and share some work with me .. it's not impossible to do all the word docs and videos but it would be much easier if there is 'team' / 'we' rather than 'me'


ospf : network type loopback  

ospf : network type loopback

The ospf network type loopback is a special case for loopback interfaces

Network type loopback is the default network type on loopback interfaces , and is not
normally configurable with ospf network command

The loopback network type treats the interface as stub host and injects the ip address of the
interface as host route into the ospf domain regardless of the actual subnet mask of the interface

setting the ospf network type to point-to-point disables this treatment and advertise the ip
address of the interface with the subnet mask configured on that interface

ospf network type : point - to - point  

ospf network type : point - to - point

OSPF network type point-to-point is used for adjacencies between exactly
two ospf neighbors

Network type point-to-point uses multicast and has no DR/BDR election

As it uses multicast for hello packet transmission broadcast keyword is used
for frame relay mapping statements .

ospf network types : point-to-multipoint non-broadcast  

ospf network types : point-to-multipoint non-broadcast

ospf network type point-to-multipoint non-broadcast is similar to
the network type point-to-multipoint except that ospf packets are sent as
unicast instead of multicast

ospf network type point-to-multipoint , point-to-multipoint non-broadcast
does not support the DR/BDR election, and possesses the same next-hop

hence layer 2 to layer 3 can be between directly connected devices on nbma network
and that ip routing will be used to communicate between devices that are not adjacent to layer 2

ospf network type : point-to-multipoint  

ospf network type : point-to-multipoint

ospf network type ponit-to-multipoint does not support DR and BDR election

point-to-multipoint sends hello packets to the multicast address

point-to-multipoint must be manually configured at the interface level using the
command "ip ospf network point-to-multipoint"

There is a difference between point-to-multipoint and the other two broadcast and non-broadcast
with the next-hop resolution on a nbma media .

ospf network type point-to-multipoint treats the network as a
collection of point-to-point links instead of one broadcast network

In broadcast and non-broadcast , ospf does not deal with layer 2 topology
and may not relate it with layer 3 network .

ospf network types broadcast and non-broadcast , next hop values are not
modified when updates are sent on nbma

This implies the device on nbma cloud requires layer 3 to layer 2 resolution
for any endpoint injecting into the network.

In ospf network type point-to-multipoint , next hop values are changed to the
address of directly connceted neighbor when they are advertised across
the NBMA cloud.

Routers on NBMA network only need layer 3 to layer 2 resolution for
directly connected neighbors when running ospf network point-to-multipoint

ospf network type point-to-multipoint advertises the endpoints of the
point-to-multipoint network as host routes instead of actual network itself

lab 4 : ospf over frame relay : broadcast  

lab 4 : ospf over frame relay : broadcast

The ospf network type broadcast sends ospf hello packets as multicast and
has a similarity of non-broadcast network type which supports DR/BDR

The neighbor statement is not required on DR or BDR

Only one hub is to be elected as dr and it can be done changing the

commands used :

show ip ospf neig
show ip ospf inte

show ip route

lab 4 vol 1 :  

Saturday, February 14, 2009

14th feb 2k9

ospf network types :

lab 4 vol 1 :

The default ospf network type for a multipoint frame relay interface is

The ospf network type non-broadcast generates unicast hello packets and
like the broadcast network type supports the DR/BDR election

Hello packets are of unicast type so neighbours must be manually
configured with neighbour statement under ospf process

DR in ospf is responsible for distributing lsa to other devices on the
segement and hence dr must have a direct layer two connectivity to all
devices on the segment

In hub-and-spoke NBMA networks , this implies that hub and only hub should be the
DR because hub is the only device which has direct layer two connectivity]
to all devices on the network


show ip ospf neigh
show ip ospf inter
show ip route

lab 01 vol 1  

Monday, February 9, 2009

Feb 09 ospf v1

lab 01:

OSPF network statement uses a wildcard mask to identify which interface or interfaces
are running the protocol.

The network statement determines which link-state area an interface belong to .

The wildcard mask of the network statement works like the wildcard mask option of an
IP access-list , where '0' indicates to check the particular bit position, binary one
indicates to ignore the particular bit position

Wild card mask doesnot relate to the IP subnet mask of an interface . It is simply used to
determine which interface/interfaces belong to the area of ospf process .

When multiple network statements are configured with overlapping matches , as in the
above case , the most specific network statement determines which are the interface will
exist in .

commands used :

show ip ospf int

show ip ospf int brief

show ip ospf int | in (Loopback [0-9] | Area)

DOC CD / command reference


To define the interface on which ospf runs and to define the area id for thos
interfaces , use the "network area" command in router confi mode .

wildcard-mask :

ip-address-type mask that include "dont care" bits .

Area-id :

Area that is to be associated with ospf address range . It can be
specified as either a decimal value or an "IP ADDRESS".

if you intend to associate areas with IP subnets , you can specify
a subnet address as the value of the area-id argument.

Usage Guidelines:

Using the wildcard-mask argument allows you to define one or
multiple interfaces to be associated with a specific ospf area
using a single command

For ospf to operate on the interface , the primary address of the
interface must be covered by the network area command.

If the network area command covers only the secondary address,
it will not enable ospf over that interface

IOS evaluation sequence :

The wildcard-mask argument is logically 'OR' ed with the
interface IP address

The wildcard-mask argument is logically 'OR' ed with the
ip-address argument in the network command

The software compares the two resulting values. If they match
ospf is enabled on the associated interface and this interface
is attached to the ospf area specified

Saturday, February 7, 2009

session 2 :

sat feb 07 2k9

network types:

point to point
point to multipoint
point to multipoint non broadcast

types of behaviour:

unicast / multicast
DR / BDR election
next-hop address

network types :

(A) broadcast :

network type is default in networks such as ethernet

hello packets are sent out using multicast

Election of dr and bdr takes place and decides the two multicast address distribution

multicast reserved addresses


The primary use of bdr is to minimise lsa replication

DR is elected based on two components : priority and router-id


0-255 ---> can be defined manually .. higher the number higher is the priority

value of '0' will make the router never to participate in election process

Router Id

Highest loopback addr and if not then highest interface ip

Can be manually set

if we have a bunch of loopbacks the higher one is selected

Interface preference :

loopback (higher ip addr) > loopback > interface addr (higher addr) > interface addr


sat feb 07

source 1:

ospf :

Ospf link state interior gateway routing protocol

uses its own transport protocol --- 89

ospf process can also be intialised from interface mode

Rules and matches for the adjacency:

hello/dead timers
stub flags

Identification / name

Ip address
ospf router-id

*mtu -- tif there is a mismatch
you can issue "ip ospf mtu-ignore" in the interface mode

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