Questions

Layer2 switch

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Layer2 switch

rajshekar455
TOPOLOGY :
===========
HOST1 ---> SWITCH1 ----> SWITCH2 ----> HOST2
A T T A
Vlan3 Vlan3

HOST1->10.1.2.3/24 HOST2 10.1.2.4/24

A = Access port
T = Trunk Port

T = Trunk Port (All vlans are allowed , VLAN1 is Native)

Below is my Doubt :

Here am able to ping from HOST1 to HOST2

Later have changed SWITCH2 Access port vlan id to 4 , now am expecting

HOST1 has to communicate with HOST2 but it is not happening.

Below is my understanding why it has to work. Please correct me if I misunderstood.

Below is the Flow am assuming :

1. Host1 is sending untagged frame to SWICH1 on access port and SWITCH1
Receives the untagged frame on VLAN3 and update its MAC-TABLE.

2. Now SWITCH1 send the untagged frame from Native VLAN1 to SWITCH2.
SWITCH2 receives the untagged frame on Native Vlan1.

Now there is no VLAN associated with Frame so SWITCH2 has to send that from
On its access port but it is not happening.
WHY ?

Clarifications

rajshekar455

Above topology not clear , plz use this topo.

HOST1 ---> SWITCH1 ----> SWITCH2 ----> HOST2
-------------- A -------T-------- T---------A---------------


A= Access Port
T= Trunk Port

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    NetMan1958

    You have HOST1 connected to SWITCH1 via a port that is in VLAN3. HOST2 is connected to SWITCH2 via a port that is in VLAN4. The switches are connected via a DOT1Q trunk and the native VLAN is 1. If that is correct, then why do you think the frame is sent untagged across the trunk? Since the port the frame came in on is in VLAN3 and VLAN1 is the native VLAN, the frame will be tagged with VLAN3 when it goes across the trunk. When SWITCH2 receives the frame, it sees the VLAN3 tag and will only forward it to a port in VLAN3. HOST2 is in VLAN4 and will never see the frame.

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    rajshekar455

    Thanks so much for quick reply.

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    0 Votes
    NetMan1958

    You have HOST1 connected to SWITCH1 via a port that is in VLAN3. HOST2 is connected to SWITCH2 via a port that is in VLAN4. The switches are connected via a DOT1Q trunk and the native VLAN is 1. If that is correct, then why do you think the frame is sent untagged across the trunk? Since the port the frame came in on is in VLAN3 and VLAN1 is the native VLAN, the frame will be tagged with VLAN3 when it goes across the trunk. When SWITCH2 receives the frame, it sees the VLAN3 tag and will only forward it to a port in VLAN3. HOST2 is in VLAN4 and will never see the frame.

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    rajshekar455

    Thanks so much for quick reply.