. . . 7th Lecture - Networking . . .

[robo]

[quote author=k2s link=topic=237832.msg2965762#msg2965762 date=1316126198]
No...... for pure Layer switches.... models below c3560

For layer 3 switches (models c3560 & above) u enable routing ( ip routing) to act as router. u can see the routing table by issuing "sh ip route"
[/quote] CITI_$D# CITI_$D# CITI_$D#

[k2s]

[move][color=blue][size=24pt]ANY DOUBTS[/size][/color][/move]

[dreamgirl]

[quote author=k2s link=topic=237832.msg2965827#msg2965827 date=1316126876]
[move][color=blue][size=24pt]ANY DOUBTS[/size][/color][/move]
[/quote]

no comment no comment

dg..

[k2s]

Ok Guys:

Next Topic : Spanning Tree Protocol (IEEE 802.1d)


The Need for Spanning Tree:


[img]http://i54.tinypic.com/2i8uff5.png[/img]

Switches flood broadcasts out all interfaces in the same VLAN, except the interface in
which the frame arrived. In the figure, that means SW3 will forward Bob’s frame to SW2;
SW2 will forward the frame to SW1; SW1 will forward the frame back to SW3; and SW3
will forward it back to SW2 again. This frame will loop until something changes—someone
shuts down an interface, reloads a switch, or does something else to break the loop. Also
note that the same event happens in the opposite direction. When Bob sends the original
frame, SW3 also forwards a copy to SW1, SW1 forwards it to SW2, and so on.



MAC table instability also occurs as a result of the looping frames. MAC table instability
means that the switches’ MAC address tables will keep changing the information listed for
the source MAC address of the looping frame. For example, SW3 begins Figure 2-1 with a
MAC table entry as follows:

0200.3333.3333        Fa0/13          VLAN 1

However, now think about the switch-learning process that occurs when the looping frame
goes to SW2, then SW1, and then back into SW3’s Gi0/1 interface. SW3 thinks, “Hmmm...
the source MAC address is 0200.3333.3333, and it came in my Gi0/1 interface. Update my
MAC table!” resulting in the following entry on SW3:


0200.3333.3333        Gi0/1            VLAN 1


At this point, if a frame arrives at SW3—a different frame than the looping frame that
causes the problems—destined to Bob’s MAC address of 0200.3333.3333, SW3 would
incorrectly forward the frame out Gi0/1 to SW1. This new frame can also loop, or the frame
might simply never be delivered to Bob.


The third class of problem caused by not using STP in a network with redundancy is that
working hosts get multiple copies of the same frame. Consider a case in which Bob sends
a frame to Larry, but none of the switches know Larry’s MAC address. (Switches flood
frames sent to unknown destination unicast MAC addresses.) When Bob sends the frame
(destined to Larry’s MAC address), SW3 sends a copy to SW1 and SW2. SW1 and SW2
also flood the frame, causing copies of the frame to loop. SW1 also sends a copy of each
frame out Fa0/11 to Larry. As a result, Larry gets multiple copies of the frame, which may
result in an application failure, if not more pervasive networking problems.

[k2s]

[quote author=dreamgirl link=topic=237832.msg2965856#msg2965856 date=1316127131]
no comment no comment

dg..
[/quote][img]http://www.imageping.com/out.php/i25672_RP7.gif[/img]

[dreamgirl]

[quote author=k2s link=topic=237832.msg2965872#msg2965872 date=1316127242]
[img]http://www.imageping.com/out.php/i25672_RP7.gif[/img]
[/quote]

naaku ee muuki gif's artham avvavu..dialogue entantaaru prof. gaaru ..  sCo_^Y sCo_^Y

dg..

[k2s]

[quote author=dreamgirl link=topic=237832.msg2965881#msg2965881 date=1316127334]
naaku ee muuki gif's artham avvavu..dialogue entantaaru prof. gaaru ..  sCo_^Y sCo_^Y

dg..
[/quote]

evaru meeru....... idi networking class....... robotics science class kadu
if interest u can join

[dreamgirl]

[quote author=k2s link=topic=237832.msg2965896#msg2965896 date=1316127474]
evaru meeru....... idi networking class....... robotics science class kadu
if interest u can join
[/quote]

join avvochu kaani naakem artham kaadhanukunta.. sSa_j@il sSa_j@il sSa_j@il sSa_j@il

dg..

[k2s]

[quote author=dreamgirl link=topic=237832.msg2965911#msg2965911 date=1316127568]
join avvochu kaani naakem artham kaadhanukunta.. sSa_j@il sSa_j@il sSa_j@il sSa_j@il

dg..
[/quote]

every day a new topic will be taught..... start from starting.... of this thread..... u will understand for sure.....

[dreamgirl]

[quote author=k2s link=topic=237832.msg2965918#msg2965918 date=1316127660]
every day a new topic will be taught..... start from starting.... of this thread..... u will understand for sure.....
[/quote]

hmm..will see, thanks anyways:)

dg..

[k2s]

Three Classes of Problems Caused by Not Using STP in Redundant LANs



Problem                                    Description

Broadcast storms                    The forwarding of a frame repeatedly on the same links, consuming
                                              significant parts of the links’ capacities


MAC table instability              The continual updating of a switch’s MAC address table with incorrect
                                                entries, in reaction to looping frames, resulting in frames being sent to the
                                              wrong locations

Multiple frame                        A side effect of looping frames in which multiple copies of one frame are
                                                transmission delivered to the intended host, confusing the host

[k2s]

What IEEE 802.1d Spanning Tree Does

STP prevents loops by placing each bridge/switch port in either a Forwarding State or a
Blocking State. Interfaces in the Forwarding State act as normal, forwarding and receiving
frames, but interfaces in a Blocking State do not process any frames except STP messages.


After STP is run....... u can see in figure :

[img]http://i51.tinypic.com/20s7p6d.png[/img]



Now when Bob sends a broadcast frame, the frame does not loop. Bob sends the frame to
SW3 (Step 1), which then forwards the frame only to SW1 (Step 2), because SW3’s Gi0/2
interface is in a Blocking State. SW1 floods the frame out both Fa0/11 and Gi0/1 (Step 3).
SW2 floods the frame out Fa0/12 and Gi0/1 (Step 4). However, SW3 ignores the frame
received from SW2, again because that frame enters SW3’s Gi0/2 interface, which is in a
Blocking State.

[ToughGuy]

sorry baaa full meeting lo vunde ivala ...time dorakaledu baa ....intiki velli choosthaaa

[k2s]

[quote author=!!!! FeRRo !!!! link=topic=237832.msg2965976#msg2965976 date=1316128235]
sorry baaa full meeting lo vunde ivala ...time dorakaledu baa ....intiki velli choosthaaa
[/quote] S%Hi

[k2s]

How Spanning Tree Works



STP uses three criteria to choose whether to put an interface in Forwarding State:
■ STP elects a root switch. STP puts all working interfaces on the root switch in
  Forwarding State.


■ Each nonroot switch considers one of its ports to have the least administrative cost
  between itself and the root switch. STP places this least-root-cost interface, called that
  switch’s root port (RP), in Forwarding State.


■ Many switches can attach to the same Ethernet segment. The switch with the lowest
  administrative cost from itself to the root bridge, as compared with the other switches
  attached to the same segment, is placed in Forwarding State. The lowest-cost switch on
each segment is called the designated bridge, and that bridge’s interface, attached to
  that segment, is called the designated port (DP).



NOTE The real reason the root places all working interfaces in a Forwarding State is
that all its interfaces will become DPs, but it is easier to just remember that the all the root
switches’ working interfaces will forward frames.



All other interfaces are placed in Blocking State.