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New Member

mac address table on C3750

I have problem with mac address learning on C3750. I need to connect two vlans on the same C3750 by external L2 box (IPS device). This box provides mapping between vlans on trunk ports. Connection is depicted below:

int vlan 370 (L3 svi interface)

|

g1/0/20 (trunk with vlan 370)

|

external box, maps vlan 370 to vlan 361

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g1/0/19 (trunk with vlan 361)

|

another switch

|

PC (in vlan 361)

But this does not work. C3750 refuses to learn mac address from L3 interface vlan 370 on interface g1/0/19 in vlan 361. When I use command 'mac-address-table static xxxx.xxxx.xxxx vl 361 int g1/0/19' all is working correctly. But I can not use this, because mac address of SVI interface changes after each C3750 reload.

Any suggestions are greatly appreciated.

2 REPLIES
New Member

Re: mac address table on C3750

I'm not sure how the external L2 box works, but maybe you have to use the 'native vlan' command on Gi1/0/19 and -20 with 370 and 361 as native vlans?

(The native vlan is transmited untagged in a trunk)

I'm not really confident about this but maybe you want to give it a try...

New Member

Re: mac address table on C3750

That box supports 802.1Q and provides mapping from tag 370 to tag 361.

In fact I need to connect more than one vlan thru, so native vlan is not usable.

I guess that C3750 refuses to learn mac address pertaining to int vlan 370 from external wire.

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