Routing between two ISP

[shanemcanuff]

I have a prob.. I want to use both flow and C&W as my ISP. I want flow to be my main ISP and C&W the 2nd, so I am goin to use load balancing, so if and when flow stop work my firewall will fail over to c&w. What I want to know is since I will be hosting my mail and web servers, the IP address will be from flow that will NAT to the servers, but when flow is down access the mails, web site and other public servers will be down. I want to know what to do, do I have to use BGP get a block of IP and tell both ISP to add it to they routing table?

1) Two ASA 5520

2) Two ASA as firewall and one internal router (I have a 2nd Cisco router as backup)

do I need a cisco router before the two ASA and have a internal router for internal use, or the ASA can do the job?

[andrew.prince]

Shane,

Have a look at the blow link:-

http://www.cisco.com/en/US/customer/products/hw/vpndevc/ps2030/products_configuration_example09186a00806e880b.shtml

HTH>

[shanemcanuff]

Andrew;

I can't get access to that link.

[andrew.prince · Accepted solution]

Shane,

Have you tried your netpro uid & pwd? if so, and it still does not work - attached is the official Cisco .pdf.

HTH>

[shanemcanuff]

yes I did, can I config.. the ASA to NAT two diff.. public IP to one server?

[andrew.prince · Accepted solution]

Yes you can - but they have to be diff tcp/udp port numbers being passed onto the internal server, and possibly on a policy based NAT access-list.

HTH>

[Steve Lyons · Accepted solution]

So remember on the internet BGP is the routing protocol. BGP uses AS-Path is one of the main factors in determining best path. So for example take your network ip range and chop it into two. With the first ISP advertise the complete network and then use as-prepend for the subset prefixes you advertise to ISP A. Then with ISP B do the same by still advertising the complete network block and the other half of the remaining prefixes and use as-prepend again. BGP uses AS numbers like rip uses hops to determine shortest path. So the more AS numbers to go through the worse the route.

Example: Network A has two paths on the internet. One through ISP A and one through ISP B. To get to Network A through ISP A you have to go through AS #50, #60 and # 70 lets say. So for example s 3 AS hops. Then lets say to get to Network A through ISP B you only have to go through AS # 90. This is only one AS hop and will be seen as the best path. If you own the Network prefix and AS # you can pre-pend as many AS #s you would like as long as it is the same number that you own. So for example let's say you owned 192.168.1.0 and BGP AS # 65412. You could send this advertisement to ISP A as network 192.168.1.0 = AS # 64512, 64512, 64512. and to ISP B network 192.168.1.0 = AS # 64512. In this case ISP B will be seen as the best path on the internet. This solution will be used for traffic coming into your network.

For traffic leaving your network you can use BGP Weight, local-preference, Default route weighting, etc. So remember on the internet BGP is the routing protocol. BGP uses AS-Path is one of the main factors in determining best path. So for example take your network ip range and chop it into two. With the first ISP advertise the complete network and then use as-prepend for the subset prefixes you advertise to ISP A. Then with ISP B do the same by still advertising the complete network block and the other half of the remaining prefixes and use as-prepend again. BGP uses AS numbers like rip uses hops to determine shortest path. So the more AS numbers to go through the worse the route.

Example: Network A has two paths on the internet. One through ISP A and one through ISP B. To get to Network A through ISP A you have to go through AS #50, #60 and # 70 lets say. So for example 3 AS hops. Then let's say to get to Network A through ISP B you only have to go through AS # 90. This is only one AS hop and will be seen as the best path. If you own the Network prefix and AS # you can pre-pend as many AS #s you would like as long as it is the same number that you own. So for example let's say you owned 192.168.1.0 and BGP AS # 65412. You could send this advertisement to ISP A as network 192.168.1.0 = AS # 64512, 64512, 64512. and to ISP B network 192.168.1.0 = AS # 64512. In this case ISP B will be seen as the best path on the internet. This solution will be used for traffic coming into your network.

For traffic leaving your network you can use BGP Weight, local-preference, Default route weighting, etc.

Steve Lyons - Cisco

[shanemcanuff]

I would like to say thx.. for the help I got from you guys.