VLAN in Two Cisco Routers

[chrislgicale]

Guys,

A pleasant day!

We have two ISP in our company. Each has Cisco router as gateway. I'm thinking if it is possible to create VLANs in these two routers.

Let's say I have VLAN100 in Router1 (192.168.100.253) and VLAN200 in Router2 (192.168.100.254). Does it create a conflict in the network?

I was observed that once I create VLAN in a router, this will automatically his internet access path.

Appreciate any idea on this. Thanks.

Regards,

Chris

[josh000014]

Hi Chris,

Are you trying to load balance between these two routers or setup for failover? If so I would use VRRP or HSRP for this.

Check out this guide for HSRP:

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/swhsrp.html

Josh

[chrislgicale]

Josh,

Appreciate your response. Thanks for the informational link. I will try to consider that.

How about I want to dedicate for example a gateway of an ISP for a particular host or VLAN. For example;

Router1(ISP) has VLAN100 configured. Computer01 is connected to VLAN100

Router2(ISP) has VLAN200 configured. Computer02 is connected to VLAN200

Router1 is a Cisco 1921

Router2 is a Cisco 1841

Is it possible that Computer02, which is a member of VLAN200 able to use Router1(ISP)?

Or, is it possible that both Cisco routers has created VLAN?

Thanks.

Chris

[josh000014 · Accepted solution]

Hi Chris,

You can put the routers in different vlans. On the directly connect switch (assuming you have just 2 vlans), put Router1 is vlan 100 and Router2 in vlan 200. Then you can choose which ISP you want the computers to go out by which vlan you put them in. If you want the computers to be able to talk to each other you can't overlap the address ranges though.

Another option would be to have all of you computers gateway to Router1 and then setup Policy Based Routing to redirect traffic to the other router. It would look something like this:

ip access-list extended ispselect 

 permit ip host Computer2_IP any

route-map isp2 permit 10

 match ip address ispselect

 set ip default next-hop 192.168.100.254

Apply this on the inside interface of Router1

ip policy route-map isp2

In this configuration, you would be able to leave everything in the same network without the need to statically vlan the PCs.

Josh

[chrislgicale]

Hi Josh,

From the first option you gave (let me know if I'm correct with your interpretation), having VLAN/s on both ISP routers will not create conflict in my network traffic. It's just a matter of IP routing to keep them two connected.

For the second option, I will check on this. I well appreciate your time helping me.

Regards,

Chris

[josh000014]

This all depends if you want the Computers to communicate despite being on separate vlans. If there is any IP address overlap you will need to allocate another address range for the other vlan. (i.e. 192.168.101.0/24).

Josh

[chrislgicale]

Hi Josh,

Going back to your suggested solution which is route-map.

What are you referring in the phrase "Apply this on the inside interface of Router1"?

Is it physical or the VLAN interface?

Thanks!

Chris

[josh000014]

Hi Chris,

You would apply this to the vlan1 interface.

Thanks!

Josh

[chrislgicale]

Hi Josh,

I was trying to configure route-map, do I need to use "sdm prefer" in the Cisco switch? To enable desktop routing?

Appreciate any response.

Regards,

Chris