2 routers connected to a switch ?

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fran1942

82 posts

Master Geek

Trusted

#151480 27-Aug-2014 09:21

Hello, I have a layer 3 switch with a VLAN 1 interface of 192.168.0.1/24.
I have two routers connected to this switch. The interface of each router is 192.168.0.100/24 and 192.168.0.254/24.
In Packet tracer this works fine, but I am breaking rules here i.e only you should have a separate network for each link ?

Thanks for any advice.

hashbrown

463 posts

Ultimate Geek

#1116286 27-Aug-2014 09:53

Two networks can co-exist on the same link, they just won't be able to communicate, so it's not a particularly useful setup.

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Inphinity

2759 posts

Uber Geek

Subscriber

#1116288 27-Aug-2014 09:54

What are you hoping to achieve by having two routers within the same subnet?

Mattmannz

471 posts

Ultimate Geek

#1116409 27-Aug-2014 12:16

No issues at all doing what you are doing as long as you are exchanging routing information between the layer 3 switch and the two routers otherwise the layer 3 switch won't know what networks exist on the other side of the two routers and therefore which router to send traffic to.

You could do it with static routes if you don't wish to use dynamic routing. I assume that the client devices will use the address of the layer 3 switch as their gateway address?

If the two routers both connect to the same networks on the far end then you need to look at your routing to make sure that it is doing what you expect ie active/standby or active/active for both routers and make sure that return traffic takes the same path.

Matt.

niekerkj

69 posts

Master Geek

#1118538 30-Aug-2014 13:43

Hi,

I had a similar question which may explain the scenario:

I have two routers, one for my standard ADSL Spark connection and a dd-wrt router permanently connected to a vpn service.

I have a HTPC which I sometimes want to connect to the DD-WRT router to watch Netflix and other times connect to my other router to watch TVNZ On Demand.

Can I connect both routers and the HTPC to the same switch? How will I switch between connections on my Win 8 HTPC?

the HTPC does have wireless, but I prefer the stability of LAN when streaming content.

Thanks
Jules

Mattmannz

471 posts

Ultimate Geek

#1118658 30-Aug-2014 17:59

Yes you can do this but you will need to know which networks you want to route over each router.

Usually you have a default gateway on your PC which points to a router. All traffic goes to this router.

If you have a second router you can add specific network routes to your PC to point them to the second router. Eg identify the networks that Netflix uses and then add route statements that send traffic for those networks to your second router.

Each router needs to have its own IP address on your network and one of them will carry the majority of your traffic and be set as the gateway on your PC.

Use the route add command to add specific network static routes to your PC.

Matt.

chrispchikin

128 posts

Master Geek

#1134439 23-Sep-2014 11:22

Bad practice to have 2 different networks running in a single VLAN off the L3 switch.

What are you trying to achieve? :)

niekerkj

69 posts

Master Geek

#1134904 23-Sep-2014 20:27

Thanks all for your replies.

My aim was to find the easiest way to connect my HTPC to both my standard NZ adsl connection amy IPVanish VPN connection.

I have now downloaded the IPVanish aplication which alloows me to easily switch between their various servers or to switch it off completely

Jules

Mattmannz

471 posts

Ultimate Geek

#1134963 23-Sep-2014 21:14

chrispchikin: Bad practice to have 2 different networks running in a single VLAN off the L3 switch.

What are you trying to achieve? :)

Not bad practice at all. If you want to share routing information between two routers then they both have to have lan addresses in the same subnet.

Matt.

chrispchikin

128 posts

Master Geek

#1135004 23-Sep-2014 21:32

Yes, but that's not what I said...

It is bad practice to have 2 different networks hanging off a single VLAN.

(E.g 192.168.1.0/24 and 192.168.2.0/24 connected to access ports in VLAN 1.)

chrispchikin

128 posts

Master Geek

#1136381 24-Sep-2014 11:18

Gah, misread OP! :P

Didn't see that the 3 IP addresses were in the same subnet...