T1 failover configuration help please!

Unanswered Question
May 1st, 2007

Hi

I have a simple topology as below

layer2 switch1 -- Router1 -- layer2 switch2 -- ISP router1 (T1) -- Internet (production T1)

layer2 switch1 -- Router1 -- layer2 switch2 -- ISP router2 (T1) -- Internet (New T1)

I have total of 2 T1s from 2 different ISPs and they are terminated on their routers which we do not manage.

Currently one T1 is in production and it is connected to a layer 2 switch and then connected to a router. Router does all the routing and hence the default route is pointed to ISP router. No routing protocols are configured on my router.

Now as I got a new T1, I would like to configure it on the same layer2 switch and the router, I would like to know if this is feasible and how can I configure the failover between the two T1s?

Thank you

Sarat

[email protected]

I have this problem too.
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Paolo Bevilacqua Tue, 05/01/2007 - 05:49

Hi Sarat,

the easiest thing is that you configure NAT on router1, then set two static routes point to ISP 1 and 2. The router will start load balancing your connections.Once you do that, you will neet to set "IP SLA" to detect problems on the ISP, this is ait more advance so I would go back to this once you have the NAT configuration working OK.

Hope this helps, plase rate post if it does!

sarat1317 Tue, 05/01/2007 - 11:42

Hi Paolo

Thanks for the reply. Does Cisco 1700 router supports IP SLA commands? I am trying to utilise most of my current equipment to redesign my network. So I am just wondering if I use a router other than Cisco in place of 'router1' and configure NAT for both T1s on that as you advised, load balancing issue would be resolved. However if I cannot configure some kind of IP SLA on that router, can I use a Cisco router that supports IP SLA feature in between "layer2 switch2" and "router1" so that this cisco router will monitor both the T1s configured through this and pass the information to "router1"? I am happy to do load balancing as well on Cisco router. Only reason I want to use other router as it will have switching, routing & firewall capabilities.

Thanks and Regards

Sarat

Paolo Bevilacqua Tue, 05/01/2007 - 12:16

Hi,

yes a recent image on the 1700 would do that.

You may have to increase flash and ram. Or you can put a 2801 and that makes a nice pbx for later. In doings this kind of things, is better to use a router.

As a courtesy to those providing answers, please rate all useful posts!

sarat1317 Mon, 05/07/2007 - 07:58

Hi Paolo

Thanks for the reply. This is a bit more complicated for me than I thought. I would like to create a setup as below referring to my first post.

(misc example)

vlan1 - 10.1.1.0/24 all outbound traffic need to go with public ip 214.24.32.33 --------> (primary T1)

vlan2 - 10.1.2.0/24 all outbound traffic need to go with public ip 214.24.32.34 --------> (primary T1) etc for vlan 3 to 6

I would like to create 6 vlans for 6 different clients and outbound traffic from each subnet should use a unique public IP assigned to the client (as a public ip is required for each client webserver for access from outside).

As I see I would require 3 fastethernet interfaces on the router (2 interfaces to terminate 2 ISPs to load balance and 1 interface for LAN).

So can you please advise what router model I can use that supports vlan configuration with 3 fast ethernet interfaces.

Can you please advise any configuration examples to achieve this setup? Can I use 1700 or 2600 series as 2801 is expensive for us.

Thank you

sarat

Paolo Bevilacqua Mon, 05/07/2007 - 08:28

Hi,

you can use any router that support VLAN trunking on fast-ethernet. It would be better if you could connect the T1 from ISP directly to the router, but if you cannot, you can create more VLAN for this and conncet via ethernet. Use decent L2 switch with VLAN support and the physical connectivity is solved.

Then for routing you will use a combination of NAT and PBR to send certain inside address to certain outside, mapping the web servers, etc.

This can be seen in more detail once you have acquired the devices and the circuits.

Good luck!

Hope this helps, please remember to rate post if it does!

sarat1317 Tue, 05/15/2007 - 09:20

Hi Paolo

Thanks for your response. I am still trying to figure out how can I configure load balancing and failover if my T1s are terminated on the ISP routers and configuring vlans as in my previous post. It would be great if you can provide me any links/configuration examples on the same.

FYI - In my setup, each client server can be given only 1 unique public IP for external access. For eg:

http://www.abcd.com (web server) is pointed to only 1 public IP x.x.x.x

As a second option, I thought to have few clients on ISP1 and few on ISP2 doing no load balancing and failover. I know this is not the best way to utilise the second link.

What do you suggest and can you advise what is the best way I can use my T1s.

Thanks for your time

Sarat

m-haddad Mon, 06/11/2007 - 13:40

Hello Sarat,

As mentioned before you can use IP SLA to monitor which T1 goes down. Using IP SLA you can send icmp ping requests to the T1 interfaces. Therefore, when the T1 is down the icmp will time out since the T1 interface goes down and the router will know that it has to route all traffic via the second ISP.

You split the traffic between ISPs but you CAN NOT load balance and the reason behind that is because each ISP will assign you a different public subnet. Therefore, ISP 1 will assign you an IP class but if you try to pass traffic to the second ISP using ISP class it will not be routed.

Therefore, best solution to use IPSLA to ping T1 Seiral Interface IP and to do several NAT statements so that you can split traffic between the ISPs.

Hope this helps,

Regards,

m-haddad Mon, 06/11/2007 - 13:43

Hello Sarat,

As mentioned before you can use IP SLA to monitor which T1 goes down. Using IP SLA you can send icmp ping requests to the T1 interfaces. Therefore, when the T1 is down the icmp will time out since the T1 interface are down. The router will know that it has to route all traffic via the second ISP.

You can split the traffic between ISPs but you CAN NOT load balance and because each ISP will assign you a different public subnet. Therefore, ISP 1 will assign you a public subnet and if you try to pass traffic to the second ISP using this ISP1 subnet it will not be routed.

Therefore, best solution to use IPSLA to ping T1 Seiral Interface IP and to do several NAT statements so that you can split traffic between the ISPs.

Hope this helps,

Remark: I corrected some written mistakes!

Regards,

sarat1317 Wed, 06/13/2007 - 08:45

Thanks for the update. Can you please advise if you any configuration example for IP SLA. I searched online but I could not find specific IP SLA configuration for T1 and what I saw is related to VOIP.

thanks

sarat

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