OSPF sub interfaces question

damien2008

If you have OSPF configured on an interface as below

Router OSPF 1
Network 192.168.1.1 0.0.0.0 area 0

If you later configure sub interfaces (router on a stick) under the same interface do you have to enter more OSPF Networks statements so that the new vlans are advertised :

tecnodog7

From my understanding your wildcard bit is saying only look at the 192.168.1.1 so in the future if you have 192.168.1.2 it won't form neighbor relationship. If you need to just do 192.168.1.0 0.0.0.255 this way everything in the .1 network will be covered in that area.

Node Man

Network 192.168.1.1 0.0.0.0 area 0 - Is an exact match to address 192.168.1.1. I would probably open up the range a bit. Maybe to something like 192.168.1.0 0.0.0.255 area 0.

Gngogh

Hi.. i dont understand why you need a routing protocol to work togheter with inter-vlan routing. A router knows what to do with all the connected interfaces... i might be wrong but i dont see the point of having a routing protocol in a scenario like this.

tecnodog7

Routers only know about the networks they are directly connected to. when we are talking about inter-vlan routing for example router on the stick, the router is getting all the packets from different vlan tags but unless you don't sepecify which vlan they belong to what is the router suppose to do with it? It's not a mind reader you know.

Gngogh

tecnodog7 wrote: »

Routers only know about the networks they are directly connected to. when we are talking about inter-vlan routing for example router on the stick, the router is getting all the packets from different vlan tags but unless you don't sepecify which vlan they belong to what is the router suppose to do with it? It's not a mind reader you know.

% Configuring IP routing on a LAN subinterface is only allowed if that subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q, or ISL vLAN.

you cannot configure an ip address on a subinterface with out first defining the type of encapsulation. if you dont do that, you are not able to configure subinterfaces.

and if you dont configure subinterfaces the router doesnt receive any packets. Did you know that???

networker050184

You don't need to run a routing protocol on a router for it to know about it's directly connected sub interfaces.

Heero

Subinterfaces are seen as completely separate interfaces to routing processes.

tecnodog7

Wait what? You don't need a routing protocol if I have subinterface connected? I'm confused. Like Heero mentioned I thought subinterfaces are like different interface so if I want to route through and from I need a routing protocol.

damien2008

my post has caused some confusion, I will post a diagram later.....

Heero

tecnodog7 wrote: »

Wait what? You don't need a routing protocol if I have subinterface connected? I'm confused. Like Heero mentioned I thought subinterfaces are like different interface so if I want to route through and from I need a routing protocol.

Routing protocols are for exchanging route information between routers. If you have one router with many interfaces and subinterfaces, it doesn't need a routing protocol. That router knows all the networks on all the interfaces and can route between.

A routing protocol would be for telling a second router "I am connected to all of these networks so route to them through me."

damien2008

So, I have now attached a diagram, my question was in order for R2 to have routes to the sub-interfaces on R1 (R1 is the router at the top of the diagram) do you have to enter more OSPF Networks statements on R1 so that the new vlans are advertised ?
R1 is the default gateway for all switches and PC in diagram

Thanks for your replies so far

Gngogh

why dont you use a layer 3 switch plug both routers to that switch and then configure hsrp.