Vlan over Routers & Switches

iangillbanks · ‎07-30-2013

Hello,

I'm trying to solve a packet tracer problem but I'm running out of ideas and could do with some suggestions/help.

I have the following setup

1 switch as the backbone, which is linked to 4 routers linked to individual switches. From here each switch is connect to a computer each on a different VLAN. So for example 1 switch is connected to a computer on Vlan 2 then Vlan 3 and Vlan 4. The second switch is also connected to 3 computers again 1 on Vlan 2, another Vlan 3 and then Vlan 4. Finally the routers are WAN connected to each other. Hope that paints the picture.

Router 1 & 2 can ping each other over the WAN connection

The routers have trunking setup for each Vlan

If I ping from a PC on Vlan 2 to another PC on the same Vlan the ping fails. The packet leaves the PC, goes through the switch and into the router then the packet is dropped. The packet doesn’t go through the WAN connection.

I’ve ran out of ideas on what to check or change to either route the packet over the WAN of through the backbone?

Any ideas?

Seb Rupik · ‎07-30-2013

Hi Ian,

can you elaborate on a your design a bit more. I assume that each router has a SVI on VLANs 1, 2, 3. Is the subnet used on each the VLANs the same across all the routers? ie, Router1's VLAN1 is the same subnet as Router2's VLAN1 ? Do the routers run a routing protocol on the interface connected to the backbone?

My suspicion is that each VLAN across the routers share the same subnet, therefore the router doesn't try to send packets to the backbone since it is directly connected to the subnet you are trying to ping, albeit with the host attached to a VLAN on another router.

cheers,

Seb.

iangillbanks · ‎07-30-2013

Thank you for the reply

Each computer is on a different subnet, so each router is connected to 3 different subnets. I've used the first IP address for the subnet on the router for the Vlan setup to the switch. So when I look at router 2 there is a new set of 3 different subnets

I've setup OSPF on the routers and when I enter the show ip ospf neighbor command each router see's each other.

Seb Rupik · ‎07-30-2013

OK, what about the output from all the routers from runnning:

show ip ospf route

iangillbanks · ‎07-30-2013

Router 1

Router>show ip route ospf

50.0.0.0/8 is variably subnetted, 11 subnets, 2 masks

O 50.25.220.4 [110/2] via 50.25.221.2, 00:13:57, Serial0/0/0

O 50.25.220.8 [110/3] via 50.25.221.2, 00:13:57, Serial0/0/0

O 50.25.220.12 [110/4] via 50.25.221.2, 00:13:57, Serial0/0/0

O 50.25.220.108 [110/3] via 50.25.221.2, 00:13:57, Serial0/0/0

O 50.25.221.4 [110/2] via 50.25.221.2, 00:13:57, Serial0/0/0

O 50.25.221.8 [110/3] via 50.25.221.2, 00:13:57, Serial0/0/0

Router 2

Router>show ip route ospf

50.0.0.0/8 is variably subnetted, 11 subnets, 2 masks

O 50.25.220.0 [110/2] via 50.25.221.1, 00:14:47, Serial0/0/0

O 50.25.220.8 [110/2] via 50.25.221.6, 00:14:47, Serial0/0/1

O 50.25.220.12 [110/3] via 50.25.221.6, 00:14:47, Serial0/0/1

O 50.25.220.108 [110/2] via 50.25.221.6, 00:14:47, Serial0/0/1

O 50.25.221.8 [110/2] via 50.25.221.6, 00:14:47, Serial0/0/1

iangillbanks · ‎07-30-2013

Think I'm getting closer....

I've ping from PC 1 on Vlan2, the packet goes through the switch, into router 1 then to the core switch.

The core switch then sends the message to router 2 where it needs to go.

The ping is to 50.25.1.130

The IP route for router 2 is as follow

C 50.25.1.128/25 is directly connected, FastEthernet0/1.2

but I don't know why the packet isn't being sent down this path? do the core switch need vlan settings?

Simon Brooks · ‎07-30-2013

Youre trying to ping in the same vlan across a routed wan? Never going to work without bgp vpnv4.

Subnets all need to be different ranges. Can you give show ip route from where you are pinging from with destination ip, eg
Show ip route x.x.x.x

Then on remote router the same command!

Sent from Cisco Technical Support Android App

iangillbanks · ‎07-30-2013

guess that stops me looking at the WAN option.

I tried sending all the packets out to the backbone switch with the command

ip route 0.0.0.0 0.0.0.0 fa0/0

on router 1 & 2 but still no join

Is this what you're looking for?

Router 1 to computer on Vlan2

Router>show ip route 50.25.0.2

Routing entry for 50.25.0.0/25

Known via "connected", distance 0, metric 0 (connected, via interface)

Routing Descriptor Blocks:

* directly connected, via FastEthernet0/1.111

Route metric is 0, traffic share count is 1

Router 2 to computer on Vlan2

Router>show ip route 50.25.1.130

Routing entry for 50.25.1.128/25

Known via "connected", distance 0, metric 0 (connected, via interface)

Routing Descriptor Blocks:

* directly connected, via FastEthernet0/1.111

Route metric is 0, traffic share count is 1

Seb Rupik · ‎07-31-2013

Hi Ian,

Is this GNS3 network you are running?

Can you provide a screenshot, and preferably the router configs?

Reading your original post, you describe the routers as connected to the backbone switch AND to eachother via WAN (serial) links. Would be good to confirm the image in my head matches the reality!

cheers,

Seb.

iangillbanks · ‎07-31-2013

Made some changes since, I've stopped looking at the WAN connection and now just using the backbone switch. I've setup OSPF DR & BDR on the routers and each switch can ping each other by going through the backbone switch.

The computers can still ping the routers but looks like the packet is lost when going through the backbone switch. I've no Vlan settings on the backbone switch. Not sure if its needed?

Maybe I could email you packet tracer file?

Thanks

Ian

Seb Rupik · ‎07-31-2013

Does the topology look like this??:

Can you post the output of: 'sh ip route', for both routers. I am still trying to get a hangle on your subnet configuration.

cheers,

Seb.

iangillbanks · ‎07-31-2013

Thats just how it looks, each computer is also on their own subnet

Router 1

Show IP Route

50.0.0.0/8 is variably subnetted, 5 subnets, 3 masks

C 50.25.0.0/25 is directly connected, FastEthernet0/1.2

C 50.25.0.128/25 is directly connected, FastEthernet0/1.3

C 50.25.1.0/25 is directly connected, FastEthernet0/1.4

C 50.25.220.0/29 is directly connected, FastEthernet0/0

C 50.25.221.0/30 is directly connected, Serial0/0/0

Route 2

50.0.0.0/8 is variably subnetted, 6 subnets, 3 masks

C 50.25.1.128/25 is directly connected, FastEthernet0/1.2

C 50.25.2.0/25 is directly connected, FastEthernet0/1.3

C 50.25.2.128/25 is directly connected, FastEthernet0/1.4

C 50.25.220.0/29 is directly connected, FastEthernet0/0

C 50.25.221.0/30 is directly connected, Serial0/0/0

C 50.25.221.4/30 is directly connected, Serial0/0/1

Seb Rupik · ‎07-31-2013

I'm not seeing any routes via a FastEthernet interface to the backbone switch. eg, no FA0/1 .

Can you provide the 'sh ip int br' for both routers?

iangillbanks · ‎07-31-2013

Looking at the routers Fa0/0 is to the backbone to the left and Fa0/1 is to the switch on the right

Router 1

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 50.25.220.1 YES manual up up

FastEthernet0/1 unassigned YES unset up up

FastEthernet0/1.2 50.25.0.1 YES manual up up

FastEthernet0/1.3 50.25.0.129 YES manual up up

FastEthernet0/1.4 50.25.1.1 YES manual up up

Serial0/0/0 50.25.221.1 YES manual up up

Router 2

Interface IP-Address OK? Method Status Protocol

FastEthernet0/0 50.25.220.2 YES manual up up

FastEthernet0/1 unassigned YES unset up up

FastEthernet0/1.2 50.25.1.129 YES manual up up

FastEthernet0/1.3 50.25.2.1 YES manual up up

FastEthernet0/1.4 50.25.2.129 YES manual up up

Serial0/0/0 50.25.221.2 YES manual up up

iangillbanks · ‎07-31-2013

Maybe to also show whats working

Green, Ping from PC to router - Works

Blue, Ping from Router to Router through the switch - Works

Red, Ping from PC to PC - Fails