MAC - port mapping problem because of STP - urgent :(

Answered Question
Apr 27th, 2009
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Hello Everyone,


I have got two 6509 connected back to back via port channel( PORT CHANNEL 1). They operate on HSRP among them with multiple vlans and sharing the active router among them. All is fine until I connect another port channel that is connecting the other building to these 6509( say port channel 4). Now if i do a show mac-add-table address command on both the 6509, i can see that the HSRP IP address, not the floating one but individual one is know know via port channel 4 rather than port channel 1 as it used to be. Because of this my EIGRP running between the two 6509s fail. Could this be an STP issue, but I have configured priorities properly on the 6509 so that none of the other switches become the root. Or could it be some one is spoofing mac-ip on the building that I am trying to connect to the 6509. Please help with this issue. Hope i have made the issue clear.

Correct Answer by Giuseppe Larosa about 8 years 2 months ago

Hello Prakadeesh,


sorry for the basic question but sometimes this happened.


and the C3750 is never STP root for any vlan ?


Any native vlan mismatch on trunk?


Hope to help

Giuseppe

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Giuseppe Larosa Mon, 04/27/2009 - 06:17
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Hello Prakadeesh,


you have two distinct port-channel 4 one on C6500_1 and one on C6500_2 ?


or you have placed in the same port-channel ports of C6500_1 and ports of C6500_2 terminated on a single switch in the other building?


In the latter case this config is not correct: a port-channel has to be between two single switches.


if you have a switch in the other building you need two distinct links one to C6500_1 and one to C6500_2


post


sh etherchannel summary

on

C6500_1

C6500_2

building_switch1

building_switch2 (if present)


Hope to help

Giuseppe


prakadeesh Mon, 04/27/2009 - 07:01
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Hello Giuseppe,


I have two different Port channels on each 6509, both terminate on the same 3750 on the other building. They just use the same name on each 6509, but are 2 different links to the building.


Thanks,

Prakadeesh

Correct Answer
Giuseppe Larosa Mon, 04/27/2009 - 07:18
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Hello Prakadeesh,


sorry for the basic question but sometimes this happened.


and the C3750 is never STP root for any vlan ?


Any native vlan mismatch on trunk?


Hope to help

Giuseppe

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