Question

how to configure two isp lines in cisco 2511 router

Asked by: trackme

Dear all,
I have a cisco 2511 router with 2 serial and 1 ethernet interface.we are planning to implement two isps on the same router.
Can you tell me how i can do this ,is it possible in this Router.
My intention is to have both the lines in the same Router,so that even when one line is down,my users can still work on the internet....ie to have a redudancy for my internet.

what is the best possible solution for that.

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Asked On
2004-03-08 at 07:44:28ID20911025
Tags

cisco

,

redudancy

,

2

,

2511

,

isps

Topic

Internet Service Providers (ISP)

Participating Experts
3
Points
200
Comments
5

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Answers

 

by: snoopy13Posted on 2004-03-09 at 01:58:06ID: 10548783

Are you going to be running any routing protocols?

If not the simplest way is to put default gateway routes to each serial interface.

ip route 0.0.0.0 0.0.0.0 S1
ip route 0.0.0.0 0.0.0.0 S0

 

by: JharperPosted on 2004-03-09 at 09:16:23ID: 10552232

If you configure it the following way then you will experience 50% packet loss whenever one of your T1s go down.

ip route 0.0.0.0 0.0.0.0 S1
ip route 0.0.0.0 0.0.0.0 S0

You'll probably have to go with BGP in your situation.  Here is are a couple of links to start with.  

Link with info about BGP
http://www.cisco.com/en/US/tech/tk365/tk80/technologies_tech_note09186a0080094820.shtml

Link with configuration examples
http://www.cisco.com/en/US/tech/tk365/tk80/technologies_configuration_example09186a008009456d.shtml

You have to be careful about configuring BGP because you can actually start routing Internet traffic through your connection if you do not have your autonomous systems setup properly.  I would work with your ISPs to set this up properly.  They will usually provide help with this.

GL
Jharper

 

by: JWarcopPosted on 2004-03-09 at 14:32:51ID: 10555533

There is a simpler answer than BGP. Purchase a similar router, put each ISP on it's own router, and use HSRP on the ethernet interfaces. This will provide hardware redundancy and redundancy to the internet. You will not be load balancing to the internet but will have a seperate connection in case one goes down.
Example:
Router1--
interface Ethernet1
  ip address 192.168.1.2 255.255.255.0
  standby 1 priority 105
  standby 1 preempt
  standby 1 ip 192.168.1.1
  standby 1 track Serial0

Router 1 uses the "standby 1 track Serial0' to track the status of the Serial Interface. If the serial interface goes down, HSRP then notifies Router 2 to take over 192.168.1.1. All clients use the gateway of 192.168.1.1.

Router2--
interface Ethernet1  
 ip address 192.168.1.3 255.255.255.0  
 standby 1 priority 100  
 standby 1 preempt  
 standby 1 ip 192.168.1.1

There is however somethink to think about-- Using this setup usually includes NAT on each router, if you are wanting to utilize a seperate firewall, you then have to revisit BGP.

Jwarcop

 

by: trackmePosted on 2004-03-09 at 23:25:36ID: 10558575

Thanks for the info,

I cant have one more Router for my network and i have make both connections in the same Router.
The Router in turn in connected to the Firewall and hence i have not enabled NAT in the Router.  Can you give a configuration example with this info ..

ISP A serial address  1.1.1.1, ethernet as 1.1.1.2

ISP B serial address  2.2.2.2, ethernet as 2.2.2.3 ,

what should be my confiuration in this case , also my firewall default route points to the etherent address of ISP A.
Should i add one more route in the firewall ,will it allow to add that also in the firewall .

This is my scenario,with this i have to build redudancy without bypassing the firewall.

20120131-EE-VQP-002

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