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New Member

Subinterface help

Bare with me guys, I'm relatively new to the field!

So I'm trying to set-up this mock network configuration and I'm having trouble getting the subinterfaces on one of my routers to come up.  I have a 3945 with an 1841 sitting behind it, and I'm having trouble getting my subinterfaces up on the 3945.

I have three vlans in this configuration:

Vlan 2 - 10.10.10.16/29

Vlan 101 - 10.10.10.24/29

Vlan 202 - 10.10.10.24/29

I have corresponding subinterfaces setup in the config, but they aren't working for some reason.  Here is my configuration for the 3945 interfaces:

interface GigabitEthernet0/0
 no ip address
 duplex auto
 speed auto
!
interface GigabitEthernet0/0.2
 description Management_10.10.10.16/29
 encapsulation dot1Q 2
 ip address 10.10.10.19 255.255.255.248
!
interface GigabitEthernet0/0.101
 description Servers_10.10.10.24/29
 encapsulation dot1Q 101
 ip address 10.10.10.26 255.255.255.248
!
interface GigabitEthernet0/0.202
 description USERS_10.10.10.32/29
 encapsulation dot1Q 202
 ip address 10.10.10.34 255.255.255.248
!
interface GigabitEthernet0/1
 ip address 10.10.10.9 255.255.255.252
 duplex auto
 speed auto

The 10.10.10.9 address is part of the 10.10.10.8/30 which is my link to the 1841.  I can ping everything else on the network through this router except for these subinterfaces, which are currently down down.

My question is do you need a physical link for the interfaces to come up?  The problem is I'm out of ports on my 1841.  If I move my connection over to the Gi0/0 port the interfaces come up but I lose my connection to the rest of the network that sits behind the 1841, which makes sense.  Is there an easier solution I'm not thinking of?  Sorry if this was vague, if you need any clarification I'd be happy to let you know what I'm thinking

Everyone's tags (1)
6 REPLIES
Purple

Re: Subinterface help

   Not sure of the question but yes you have to have a live connection on g0/0 for those interfaces to come up and be part of the routing table. Why wouldn't you have a connection on g0/0?   The connection for g/0 would normally be a trunk link down to a user switch .

New Member

Subinterface help

Well that's usually what I would do, but my network is designed like 3945 -> 1841 -> 3750, so I'm passing through another router before I hit the switch.  I guess the question is how can I have the subinterfaces as well as a global on one link?

New Member

Subinterface help

I have had issues similar to this on my 7609, not sure if its a command for the 3945 but try putting access after the int command

interface GigabitEthernet0/0.202 access


hth
Wayne
New Member

Re: Subinterface help

If g0/0 connected to 3750 directly it would be worked. You must to configure inter vlan routing on 1841, that is best practices.

Or if you want that vlan on gi0/0 and g0/1 be in same vlan you can try to use bridge-group.

Subinterface help

Did you set the encapsulation on the 1841?

this is just half config

Alessio

New Member

Subinterface help

Thanks for all the responses guys.  I was wondering if there was any way to run the subinterfaces over one physical connection that also required a global ip, but I ended up just setting up another trunk link between the 3945 and the 3750.  This might not be the most efficient way, but it definitely is working for now.

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