paolo bevilacqua Mon, 05/14/2007 - 12:59
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Same thing. In the past existed fddi and token-ring that used a different method for bridging, but these are gone by long time.

mohammedmahmoud Mon, 05/14/2007 - 13:01
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Hi,


I don't think that technically there is a difference.


Ethernet LAN switches use Transparent Bridging to create the address lookup tables. Transparent bridging technology allows a switch to learn everything that the switch needs to know about the location of nodes on the network without the need for the network administrator to do anything. Transparent bridging has five parts (Learning, flooding, filtering, forwarding and aging).



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Mohammed Mahmoud.

dangal.43 Mon, 05/14/2007 - 13:06
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so it learn the MAC address of the HOST on the base of the source MAC address of the frame is that correct?

mohammedmahmoud Mon, 05/14/2007 - 13:09
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Hi,


Yes you are right, in brief;


. Learning

Initially when the switch gets the first frame of data from a node connected to a switch port. The switch reads the source MAC address and saves the address to the lookup table for this port. (Any future frames destined to this MAC are sent out this port)


. Flooding

Since the switch initially does not know where other nodes reside (the MAC table is not completed yet), the switch sends the frames to all the segments (switch ports). But the switch does not send the frames to the segment (switch port) on which the frames arrived.


. Filtering

The switch ignores frames that travel between nodes on the same segment (switch port). Same segment doesn?t need switching.


. Forwarding

After building the full MAC table, the switch by then knows the addresses of all nodes on all segments; the switch sends the frame directly to the specified node on the corresponding switch port according to the MAC table. In case that the nodes are on a different segments (switch ports), the switch must connect the two segments to send the frames.


. Aging

The switch has a user-configurable timer that erases the MAC entry after a certain length of time of no activity from that node. The erasure frees up valuable memory resources for other entries.



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Mohammed Mahmoud.

dangal.43 Mon, 05/14/2007 - 13:25
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I am configuring the trunking between two switch and what are the possible combination of the status like auto, desirable etc. on both the ends and what is DTP in switching technology?



mohammedmahmoud Mon, 05/14/2007 - 13:34
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Hi,


Cisco switches (Only Cisco switches and not the routers ? routers' Ethernet interfaces need to be manually configured to act as Trunks) use the Dynamic Trunk Protocol (DTP) to dynamically learn whether the device on the other end of the cable wants to perform Trunking and, if so, which Trunking protocol to use.


DTP learns whether to trunk based on the DTP mode defined for an interface, Dynamic Trunking Protocol (DTP) manages trunk autonegotiation on LAN ports. DTP supports autonegotiation of both ISL and 802.1Q trunks as follows:


Auto - Create the trunk based on the neighbor request (as the neighbor wishes)

Desirable - Tell the neighbor that it prefers being trunk (i like to trunk) - default

On - Tell the neighbor Trunk regardless the neighbor (forces a trunk and tells the neighbor)

Nonegotiate - Trunk regardless the neighbor (DTP disabled / the neighbor must be configured as ON)

Off - Trunk is not allowed regardless the neighbor (trunk not allowed at all)




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Mohammed Mahmoud.

mohammedmahmoud Mon, 05/14/2007 - 14:49
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Hi,


To answer your question about the combination:



ON mode puts the interface into permanent trunking mode and negotiates to convert the neighboring link into a trunk link - The interface becomes a trunk interface if the neighboring interface is set to ON, Auto, Desirable or nonegotiate.

Auto - The interface becomes a trunk interface if the neighboring interface is set to trunk(ON) or desirable mode.


Desirable - The interface becomes a trunk interface if the neighboring interface is set to trunk(ON), desirable, or auto


nonegotiate - Prevents the interface from generating DTP frames. You can use this command only when the interface switchport mode is access or trunk. You must manually configure the neighboring interface as a trunk interface to establish a trunk link.



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Mohammed Mahmoud.

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