Cisco 1841 with Ethernet + ADSL as Resilient

[nsurti273]

Hi,

I have a cisco 1841 router in place. I also have a ADSL module which fits into the cisco router. My understanding is that if configured correctly, If the primary circuit were to fail (Ethernet Circuit MPLS), the ADSL would take over services until such time the ethernet link becomes available.

Therefore the ADSL circuit is used as a resilient link.

If this is possible, can the Cisco 1841 be setup to automatically switch over to the ADSL? Would there be some sort of heart beat between the ethernet circuit and adsl circuit?

Also from the other end of the Cisco router, the connection goes into a firewall. If the Cisco handles the failover, I assume I would not need to configure anything on the firewall.

The end users beyond the firewall, should be able to continue, however the performace would be degraded?

If you need further information, please do not hesitate to ask.

Thanks in Advance

Narendra Surti

[cadet alain]

Hi,

yes it's possible to achieve using IP sla and floating static route. what routing protocols are you running on the CE-PE link for MPLS ?

No you won't have to do anything on the firewall.

performance-wise it will depend upon ADSL link speed and as you will go over internet you won't be able to do QoS anymore and your latency may vary widely according to status of the path you're taking between your endpoints.

You won't have stateful NAT either with only one router.

Regards.

Alain

[nsurti273]

Alan,

Thank you for your prompt feed back.

We are using the MPLS for DIA, SIP and IPSEC.

I have two Ciscro routers, head office and branch office. The aim was that if any of the MPLS circuits go down the ADSL would take over. However at the time of installation, the engineer who attended site advised that this was not possible and that we would need to replace out existing firewall, so the ADSL could be plugged directly into the firewall?

I have a meeting with the supplier to review this with them tomorrow and I aim to tell them that we should not need to replace firewall, but the automatic routing should be handled by the Cisco 1841.

I an not concerned about QOS, our main aim if to have a contingency in so emails can get delivered into our email server.

I have a setup with messagelabs for emails to be routed over out primary IP address, however if that fails, the system can delivery via our secondary route. Which should be the ADSL ipaddress.

Narendra

[cadet alain]

Hi,

what was the engineers reason for replacing the firewall?  if it is between your LAN users and the router then I don't see why you should modify the firewall settings, are you doing the NAT on the router? Which firewall is this?

Regards.

Alain.

[nsurti273]

Alan,

Our firewall is between the Cisco router and the LAN.

I beleive the engineer may not understand what programming can be done on the Cisco 1841.

You ask if we are doing NAT on the router? I assume you mean on the ADSL router? If so I beleive we will need to set this up with NAT for this to work?

Narendra

[cadet alain]

Hi,

No I'm just asking if you're doing NAT on the router or on the firewall

Regards.

Alain

[nsurti273]

Alan,

Apologies, Our NAT is on the firewall.

Narendra

[nsurti273]

Alan.

I have had a little progress from our supplier. They say the ADSL Module in the Cisco 1840 can be used as a backup providing the MPLS Circuit and the ADSL Resilient link are from the same provider, therefore can be within the same IP address range?

Any thoughts?

I was planning on using the MPLS and say and standard ADSL circuit from BT.

[cadet alain]

Hi,

I don't understand why they should be from the same provider ? for failover you simply need 2 default static routes, the primary is controlled by IP SLA and has default AD and the backup has a higher AD and will only be installed when primary is down. Which protocol are you running on the MPLS link? static, RIP, EIGRP,OSPF,BGP ?

Regards.

Alain

[nsurti273]

Alan,

I am not sure of what protocol we are using, however I was advised yesterday that we need BGP, so I take it we are not using that.

We were also advised that we can only run this with a PAB (Private Access Broadband).

[cadet alain]

Hi,

to advise you correctly we need to know what routing  protocol you are running for your MPLS VPN and on what layer 2  infrastructure.

Why would you need BGP ? Do you need to be accessible from the internet because you're offering a service to customers?

Regards.

Alain

[nsurti273]

Alan,

I will try and find out what protocols are being ru on our MPLS. As far as services accessible from the interner. Our primaryu concern would be delivery of our external emails. We are not concerned about any other services provided over the internet.

Our business relies on imcoming emails from clients with intructions. So the ability to receive emails is highly critical.

Narendra