Two ISPs, Two Serial Interfaces, One Router

[rumerley]

All:

I've gone through a lot of the previous posts on this forum and I'm still up in the air as to a solution to my dilemna. Also, I'm a novice at this so bear with me.

We had one T1 through ISP_A (141.xxx.xxx.xxx) going through a Cisco 2621. We have added an additional T1 through ISP_B (65.xxx.xxx.xxx). My router currently has two CSU/DSU cards (Serial0/0 and Serial0/1).

Now, I understand that in order to perform loadbalancing or load sharing I need to use BGP (acquire an ASN, etc). What I am interested in doing instead is use the new line through ISB_B as a failover. I'm still debating routing our different subnets through their own interface, but that is for a future discussion.

I've looked into HSRP for the failover and I'm having problems finding any solutions that only use one router. Is there a way to configure failover in a single router with two serial interfaces and two ISPs? If so, what configuration commands should I look into.

Since we're not really providing any sites for our clients here, and this would primarily be for outbound access, I'm not interested in BGP.

Thanks in advance for your time.

 

[rn4it]

You would still use BGP for failover, I'm not an expert in BGP, but I have looked into a similiar issue. What I was told in short is:
1 - You'll have to have tech's from both ISP's involved.
2 - They will be leary in doing it, but will.
3 - It will be expensive.

We are currently using BGP in our Internet router, have 1 connection go to our ISP in 1 city, and a shadow line go to our ISP's in another city. When the main line fails, the shadow line kicks in BGP recalculates routing table and up and going in a heart beat. When the main line kicks back in, BGP recalculates the routing table and we're going back through the main line.

hope this helps

 

[trevorh13]

Could you not simply configure two default routes? One pointing to your ISP A with a metric of 1 and one to ISP B with a Metric of 2. It should only use the link via ISP B if ISP A is unreachable. I have done this with Static routes but never tried it with the default route with Cisco.

 

[rn4it]

The only problem with that (using static/default routes) is if a router goes down with in the ISP, but you don't lose link. You will keep sending your traffic out that interface (the metric of 1). So you would have to mannually make a change. It's cheaper and easier, but not as resiliant. The question for rummerley is how important is the Internet to your company, if it's mission critical then don't mess around, if it's just used 9-5 research, email and a web presense (no e-commerce) then trevorh13's solution may be ok to use.

good luck

 

[tschouten]

Try something like this, this is just a lab example but it should be what you are looking for and it will work.

hostname R2
!
enable password ww
!
!
!
!
!
ip subnet-zero
no ip finger
no ip domain-lookup
!
!
!
interface Ethernet0
description Local LAN
ip address 172.31.10.2 255.255.255.0
!
interface Serial0
description Primary Link to R1
ip address 10.10.10.2 255.255.255.252
clockrate 56000
!
interface Serial1
description Backup Link to R1
ip address 192.168.20.2 255.255.255.252
!
interface TokenRing0
no ip address
shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 10.10.10.1
!---This is the primary default route.
ip route 0.0.0.0 0.0.0.0 192.168.20.1 250
!---The floating default route to be used if the T1 fails.
no ip http server
!
!
line con 0
exec-timeout 0 0
transport input none
line aux 0
line vty 0 4
password ww
login
!
end