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How Redundancy with 2 lines Internet Access

I've 2 links to internet access ... one DS3 and a 2T1...and I've one router 3845 Cisco...(only one router) ...the question's how I configure on this router the high avalivity with 2 links ...

The ISPs are diferents, in this routers we've 9 tunnels site to site, and behind my netowrk we've public servers, VPN Remote acceso with ASA...

The solution or strategy for this redundancy in my lines should be with one router only.

  • WAN Routing and Switching
New Member

Re: How Redundancy with 2 lines Internet Access

If you have a range ip and ASN own, you can config two sessions BGP.

Or if you have a range ip own but you haven't a ASN, you can install high available with static route and distance administrative.


Re: How Redundancy with 2 lines Internet Access

Are your T-1's bound together or is it really 3 links?

With this type of set-up you will want to have your own ASN and IP space.

Then run BGP with the peers. If you want to use the lines at the same time it will be a different config than running on one connection and the others for failover.

Re: How Redundancy with 2 lines Internet Access

So, the next week i will be a my ASN, I understand that I should be change my 2 public ip ranges by one new ip public range.

I undertand that my ISPs should be give the internet access by BGP.'s correct ?

Now, what configuration, protocol or strategy i need implement on the routers for have high availivity with my 2 internet providers .


Re: How Redundancy with 2 lines Internet Access

BGP will provide this for you.

In your peering sessions you will announce the same block out to both providers. Make sure your providers do not prepend your announcement and that they will just forward to their upstream your network.

Your traffic inbound will be determined by metrics, not everyone will come in on the same path. Your outbound traffic will work much the same way. When peering with your ISP's you might want to get full routes from them, BUT make sure you have enough memory. The routing tables are rather large and having both ISP's send them will eat up a lot of memory. Make sure you have no less then 256k

New Member

Re: How Redundancy with 2 lines Internet Access


I prefferd u ple go with OER or if this is not possible then you can buy link proof branch which is the load balancer because with 2 different isp's ,it will depends on isp's how they are supporting you ,and also one big issue is public and private AS number.

And through load balancing protocols like (GLBP and HSRP..)redundency is possible but load shearing is possible in place of load balancing .

Thanks ,