Cisco Static Routing Issues

[Sir Asvald]

Hello guys and girls.

 

I'm in a situation where I've got a Cisco 2651xm and a Cisco 3550 L3 switch. I've got on a static route

 

The 2651xm is using the 192.168.0.0 network and the L3 Switch is using the 172.16.105.0 network.

 

I can ping from one side to another. The only thing I'm having one issue, and that issue is that the L3 switch cannot reach my Router (Virgin Media Which connects to the internet)

 

For example. I only can ping from switch to router. 

 

                                                                     Static Route Between them

            Virgin Media Router ---> Switch ---> Cisco router ---> L3 Switch

 

 

Thanks For you help.

 

 

[Footy]

you've given limited information, but....

I'd guess that when your traffic is going from L3 Switch to the Virgin Media Router, It is being routed on the Cisco Router, then Virgin media router doesnt know about the return subnet.

I dont know if you can set that static route on the virgin router, but you should be able to setup a NAT on the cisco router for traffic coming from the L3 switch to the Virgin router, which will allow the return traffic.

[Sir Asvald]

you've given limited information, but....

I'd guess that when your traffic is going from L3 Switch to the Virgin Media Router, It is being routed on the Cisco Router, then Virgin media router doesnt know about the return subnet.

I dont know if you can set that static route on the virgin router, but you should be able to setup a NAT on the cisco router for traffic coming from the L3 switch to the Virgin router, which will allow the return traffic.

Traffic is going from Virgin Media --> Cisco Router --> Cisco Switch

[brwainer]

Is the Cisco router doing NAT or have a firewall of any sort? That would explain why you can effectively ping out from the inside of the cisco router, and not in (assuming the L3 switch as LAN and plain switch as WAN)

If the cisco router is purely a router (as in it just routes packets, and doesn't do NAT), then you may need to set a route in the Virgin Media router for the 172 subnet., with the cisco as the gateway

[Sir Asvald]

Is the Cisco router doing NAT or have a firewall of any sort? That would explain why you can effectively ping out from the inside of the cisco router, and not in (assuming the L3 switch as LAN and plain switch as WAN)

If the cisco router is purely a router (as in it just routes packets, and doesn't do NAT), then you may need to set a route in the Virgin Media router for the 172 subnet., with the cisco as the gateway

The Cisco router is not doing any NAT. I don't think It supports it. 

[LAwLz]

Is this what your network looks like?

 

And the problem is that you can't ping from the L3 switch to the Virgin Media router?

If that's the case could you please, if it doesn't give away too much about your network, post the output you get from the show run command on each device?

If you can't do that then here are the things I recommend you check:

 

1) Check if all interfaces are up. Just check if the command shutdown is on any if the interfaces that connects them together. If that is on then make sure all routed interfaces got an IP.

2) Check if the layer 3 switch got routing enabled. If it is not enabled globally as well as on ports (with the command no switchport) then your L3 switch will just act as a layer 2 switch. I don't know if that's what you want though.

3) Make sure you got all the static routes needed. Assuming that you don't use any routing protocol at all, you will need two or three static routes on each device (depending on if you use L2 or L3 functionality on the L3 switch).

 

You could also just do a show ip route on the L3 switch. If you can't see the 192.168.0.0 network in there, or 0.0.0.0 then that's the problem. The L3 switch doesn't know how to reach the Virgin Media router's network.

[brwainer]

The Cisco router is not doing any NAT. I don't think It supports it.

In that case my second paragraph applies. Makes sure the Virgin Media router has a statuc route for the 172 subnet

[Sir Asvald]

Is this what your network looks like?

Capture.PNG

 

And the problem is that you can't ping from the L3 switch to the Virgin Media router?

If that's the case could you please, if it doesn't give away too much about your network, post the output you get from the show run command on each device?

If you can't do that then here are the things I recommend you check:

 

1) Check if all interfaces are up. Just check if the command shutdown is on any if the interfaces that connects them together. If that is on then make sure all routed interfaces got an IP.

2) Check if the layer 3 switch got routing enabled. If it is not enabled globally as well as on ports (with the command no switchport) then your L3 switch will just act as a layer 2 switch. I don't know if that's what you want though.

3) Make sure you got all the static routes needed. Assuming that you don't use any routing protocol at all, you will need two or three static routes on each device (depending on if you use L2 or L3 functionality on the L3 switch).

 

You could also just do a show ip route on the L3 switch. If you can't see the 192.168.0.0 network in there, or 0.0.0.0 then that's the problem. The L3 switch doesn't know how to reach the Virgin Media router's network.

Yes that is the network. I've checked everything. My friend has gone over it and said it should be working.

 

I've issued the command on the switch: CORE-NET-R1(Config)# IP route 0.0.0.0 0.0.0.0 192.168.0.1

 

I can also ping from router to swtich, switch to router.

 

I will try to resolve it later as I am not at home. 

[LAwLz]

Yes that is the network. I've checked everything. My friend has gone over it and said it should be working.

 

I've issued the command on the switch: CORE-NET-R1(Config)# IP route 0.0.0.0 0.0.0.0 192.168.0.1

 

I can also ping from router to swtich, switch to router.

 

I will try to resolve it later as I am not at home. 

ip route 0.0.0.0 0.0.0.0 192.168.0.1 won't work if the switch doesn't know the way to the 192.168.0.0 network.

If you change the 192.168.0.1 to 172.16.105.1 (assuming that's the IP of the router connected to the switch) then it might work.

[Wombo]

Yes that is the network. I've checked everything. My friend has gone over it and said it should be working.

 

I've issued the command on the switch: CORE-NET-R1(Config)# IP route 0.0.0.0 0.0.0.0 192.168.0.1

 

I can also ping from router to swtich, switch to router.

 

I will try to resolve it later as I am not at home. 

Ensure the switch has the global configuration command "ip routing", otherwise it will not make forwarding decisions based on IP addresses.

 

Also as LAwLz has said the switch does need to know how to reach that address of 192.168.0.1, which I'm assuming is the interface IP of your gateway/virgin device. If you are using the ip route command just point it to the interface of the Cisco router that is shared by the L3 switch. From there ensure your Cisco router can also reach the internet via the virgin media device.

 

Switch - (Config)# IP route 0.0.0.0 0.0.0.0 172.16.105.1 (Interface IP for the router between the router and L3switch)

Router - (Config)# IP route 0.0.0.0 0.0.0.0 192.168.0.1 (Interface IP of the default gateway/virgin device)

 

Also make sure you remove the old ip route command otherwise you could have quite the recursive routing problem.

 

CORE-NET-R1(Config)# no ip route 0.0.0.0 0.0.0.0 192.168.0.1

[Sir Asvald]

Ensure the switch has the global configuration command "ip routing", otherwise it will not make forwarding decisions based on IP addresses.

 

Also as LAwLz has said the switch does need to know how to reach that address of 192.168.0.1, which I'm assuming is the interface IP of your gateway/virgin device. If you are using the ip route command just point it to the interface of the Cisco router that is shared by the L3 switch. From there ensure your Cisco router can also reach the internet via the virgin media device.

 

Switch - (Config)# IP route 0.0.0.0 0.0.0.0 172.16.105.1 (Interface IP for the router between the router and L3switch)

Router - (Config)# IP route 0.0.0.0 0.0.0.0 192.168.0.1 (Interface IP of the default gateway/virgin device)

 

Also make sure you remove the old ip route command otherwise you could have quite the recursive routing problem.

 

CORE-NET-R1(Config)# no ip route 0.0.0.0 0.0.0.0 192.168.0.1

 

ip route 0.0.0.0 0.0.0.0 192.168.0.1 won't work if the switch doesn't know the way to the 192.168.0.0 network.

If you change the 192.168.0.1 to 172.16.105.1 (assuming that's the IP of the router connected to the switch) then it might work.

I've tried it, still didn't not work.

[LAwLz]

I've tried it, still didn't not work.

Then I will need the config file in order to help you.

Which static routes do you have configured on each device? You will need quite a few to get everything working.

 

 

 

Here is a quick config I threw together in packet tracer.

hostname Virgin

!

!

interface Loopback1

 ip address 1.1.1.1 255.255.255.0

!

interface FastEthernet0/0

 ip address 192.168.1.2 255.255.255.0

!

ip route 0.0.0.0 0.0.0.0 Loopback1

ip route 172.16.105.0 255.255.255.0 192.168.1.1

!

end

hostname Cisco

!

interface FastEthernet0/0

 ip address 192.168.1.1 255.255.255.0

!

interface FastEthernet1/0

 ip address 172.16.105.1 255.255.0.0

!

ip route 0.0.0.0 0.0.0.0 192.168.1.2

!

end

hostname L3_Switch

!

ip routing

!

interface FastEthernet0/1

 no switchport

 ip address 172.16.105.2 255.255.255.0

!

ip route 0.0.0.0 0.0.0.0 172.16.105.1

!

end

 

 

You will also need one or more static routes on the virgin media as well as the Cisco router that points at the networks connected to the L3 switch. You will need to configure those networks on an SVI on the L3 switch.

[Wombo]

I've tried it, still didn't not work.

 

 

Then I will need the config file in order to help you.

Which static routes do you have configured on each device? You will need quite a few to get everything working.

Yes, configs for both Cisco devices and the interface IP of your gateway please.

 

Edit: the biggest issue may be with the Virgin device not knowing how to reach back to the 172 network. If you can't configure any routes on the virgin device you will need to configure NAT on the Cisco router. you may also need a static route pointing back to the L3 switch, this depends on your addressing scheme tho.

[leadeater]

Yes, configs for both Cisco devices and the interface IP of your gateway please.

 

Edit: the biggest issue may be with the Virgin device not knowing how to reach back to the 172 network. If you can't configure any routes on the virgin device you will need to configure NAT on the Cisco router. you may also need a static route pointing back to the L3 switch, this depends on your addressing scheme tho.

 

Would agree here, the biggest issue you will have is setting up routes on AIO home routers (crap ones just don't let you). The Virgin router will be able to ping the router interface on the same subnet just fine, no routing is required so no problem there. Unless you have actually added the static route to 172 on the Virgin router it's not going to work and it's not a config issue on any of the Cisco equipment.

 

Do a ping from the router using the 172 interface to the Virgin router and you wont get a reply, that will confirm if you have the routing setup correctly on the Virgin router.