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Can I sub-interface this 6500 blade?

I have a 6500 with a WS-X6724-SFP blade

in it and IOS 12.2(18)SXE3.

I need connect a 3750 switch to one of the SFP ports on the blade. This 3750 switch will have PC's and IP phones connected and will have a data and voice vlan.

data vlan = 6

voice vlan = 910

I want to make the ws-x6724 port a routed port with sub-interfaces for the two vlans. The commands take, but I cannot ping the switch, nor can the switch ping the router port.

I remove the sub-interfaces, re-address the primary interface and I can ping the switch.

Config with sub-interfaces that does not work:

interface GigabitEthernet3/24

no ip address


interface GigabitEthernet3/24.6

encapsulation dot1Q 6

ip address

Config without sub-interfaces which works:

interface GigabitEthernet3/24

ip address

3750 switch config:

All interfaces are:

switchport access vlan 6

int vlan 6

ip address

ip default-gateway

Can the ws-x6724-sfp do sub-interfaces and if so why do you think I can't ping the switch?

Cisco Employee

Re: Can I sub-interface this 6500 blade?

Hi Friend,

I believe the reason is when you create sub interface you are specifying dot1q tag for vlan 6 but on 3750 switch the port is configured as an access port which will send the vlan 6 traffic without any tag and cat 6k subinterface will drop the traffic.

So try to configure the 3750 switchport as trunk port and allow vlan 6 only or on the subinterface dot1q command specify native keyword after vlan number something like this

encapsulation dot1Q 6 native

Try this and update if it works.



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Re: Can I sub-interface this 6500 blade?

Thats the hard way to do it , just create your layer 2 vlans on each side then create the corresponding layer 3 SVI's . Then create your trunk link between the 2 switches. Don't really get your addressing your vlan 6 addresses on each side are in different subnets so I don't know how it could work at all . on the 6500 it is in the 161.2.6 and on the 3750 it is 164.72.6 .

Community Member

Re: Can I sub-interface this 6500 blade?

I made a mistake on the IP address in the 3750 switch - it should be:

int vlan 6

ip address

ip default-gateway

Thanks for you ideas and I'll give it a try also.

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