Default Routes one goes down?

[kmcelroy]

We currently have 4 T1's coming into our route 2 from SBIC and 2 from Sprint. We are using static routing. In my routing table I have the following:


ip route 0.0.0.0 0.0.0.0 serial0 SPRINT1
ip route 0.0.0.0 0.0.0.0 serial0/1 SPRINT2
ip route 0.0.0.0 0.0.0.0 serial1 SBIC1
ip route 0.0.0.0 0.0.0.0 serial1/0 SBIC2

This weekend Sprint had an issue that caused the two T1's to go down. My customers on SBIC IP's said they could not surf on the net?? My question is I thought that with this setup if one route goes down it will default to the next route? I am wanting a setup that if SPRINT has an issue goes down that all traffic will exit my SBIC1 and SBIC2 could I just add an Administrative Distance to the SBIC1 and SBIC2 ??? Any help would be appreciated


Kris

 

[ckhanna]

Yes, consider putting an admin distance in the following order:

ip route 0.0.0.0 0.0.0.0 serial0 SPRINT1
ip route 0.0.0.0 0.0.0.0 serial0/1 50 SPRINT2
ip route 0.0.0.0 0.0.0.0 serial1 100 SBIC1
ip route 0.0.0.0 0.0.0.0 serial1/0 150 SBIC2

This will prefer your first Sprint T1 and keep failing over to the next default route.

Good luck...

-Charlie

 

[svermill]

Administrative distance is used at the point where the router selects routes for the forwarding table. To set these at different values will cause the T-1s to go completely unused as long as there is a lower value route available.

Don't know enough about your network to suggest a good alternative. This gets messy.

 

[kmcelroy]

That is what I was thinking, now I have a quick question what if I did this

ip route 0.0.0.0 0.0.0.0 serial0 50 SPRINT1
ip route 0.0.0.0 0.0.0.0 serial0/1 50 SPRINT2
ip route 0.0.0.0 0.0.0.0 serial1 100 SBIC1
ip route 0.0.0.0 0.0.0.0 serial1/0 100 SBIC2

Would this achieve load balancing on sprint then when Sprint went down would this work on SBIC?


Kris

 

[svermill]

Yes it would do that. You might want to look into BGP at this point or at least search on CCO for "dual homed ISP." There are some static route options available to you but they require a bit of research.

Are Sprint and SBIC advertising each others IPs? In other words, if you have hosts with SBIC assigned IPs, is Sprint advertising that it can route for those hosts? Vice versa?

 

[kmcelroy]

Currently they are not advertising these IP's. I want to go to BGP in a real bad way, but I need some technical advice (how to set it up). We purchased an ASN and are ready to migrate, but I have no IDEA on where to actually start with this project. All in all would be willing to pay an individual to help me take on this project and help me with maintaining untill I got the feel for it.

Kris

 

[svermill]

Kris,

Cisco publishes a set of criteria for implementing BGP. You will find these criteria on CCO and in all of the Cisco Press routing books. One of the primary items listed is a COMPLETE and THOROUGH understanding of BGP. So I would recommend that whoever you hire be local to your area so they can show up on site if necessary.

Here is a good place to get started (requires login):

http://www.cisco.com/cgi-bin/Support/PSP/psp_view.pl?p=Internetworking:BGP

If you don't have a login, just search CCO for BGP. You'll get more than you ever wanted about BGP.

Back to your immediate problem....if your ISPs don't advertise the others address space, you may have a problem. For example, with your SBIC routes mothballed as floating static routes, how will the internet reach your SBIC hosts? I think there are some crazy NAT configurations and some policy routing features that can help alleviate the problem, but I've not been up against it myself.

 

[saleen351]

router 1
s0 = sprint
s1 = sbc

router 2
s0 = sprint
s1 = sbc

r u looking for redundacy or symettry?