Re: Configuring new serial int - Page 2

warwickconstruction · ‎03-21-2006

Hello,

I have posted on here a few times before and you guys have been very helpful. So here goes!

I have an existing Cisco 2621XM. It is connected to an external DSU via an ehternet crossover cable. I am about to get another T1 into the building from the same ISP but on a new DSU. I plan to buy 2 WIC-1T interfaces and use them to connect to both the DSUs. The DSUs are Adtran 608. They have v.35 interfaces. So, I relise this is asking a lot but could anyone help me with the best way to configure my router to use this config? I am a complete newb when it comes to Cisco and though I can use the command line and change settings, I have no idea about the best way to do this.

Please let me know if you need any more info.

I appreciate any help you can give me.

Paul

pkhatri · ‎03-22-2006

Hi Paul,

With Ethernet interfaces, it is best to use a route such as the following:

ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 xx.xx.xx.xx

This is because it's a multiaccess interface and you are better off pointing to a next-hop address on that interface. If you don't, your router will send out unnecessary ARPs for every single address ...

Hope that helps - pls rate the post if it does.

Paresh

warwickconstruction · ‎03-23-2006

Hi Paresh,

When I use the route ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 xx.xx.xx.xx

I loose connection to the T1. I am assuming of course that xx is the next hop. IE the default gateway I have set up in my

ip route 0.0.0.0 0.0.0.0 xx.xx.xx.xx

It works if the other route is stll in there but if I remove it, it stops working...

Any ideas?

Thanks

Paul

warwickconstruction · ‎03-23-2006

Ok, I experimented a little. When I enter the command

no ip route 0.0.0.0 0.0.0.0 xx.xx.xx.xx

To see if it will work with just the

ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 xx.xx.xx.xx

It removes both the route. Neither are in the sh ip route where as, before I entered the no ip route comand mentioned above they were both visable....it also removed the

ip route 0.0.0.0 0.0.0.0 FastEthernet0/1 xx.xx.xx.xx

line from the config.....

It seems I am doing something wrong!

pkhatri · ‎03-23-2006

Hi Paul,

Can I calrify what exactly you want to achieve at the moment...

1. You have an internet link via Fast0/1 and another via a T1

2. You want to load-balance over the two links

Is the above correct or do you want to use the links in a primary/backup fashion ?

Paresh

warwickconstruction · ‎03-23-2006

Hi Paresh,

I think I am confusing the issue. It would be better to wait until my second T1 is installed! I will immplement the suggestions you have lredy given me nd then post on my progress. Thans for your help so far

Paul

pkhatri · ‎03-23-2006

Hey Paul,

That's what I was kinda getting at...

Post back when you get the second T1.

Regards,

Paresh

warwickconstruction · ‎03-24-2006

Hi Paresh,

It seems I have a problem! I was informed lte yesteday that our existing Adtran DSU from our ISP will not be able to use v.35. The only way this Adtran can deliver service is over the ethernet port. This is, as I have said, the way we have it now. The new Adtran will be able to use v.35. So, with this in mind, how best can I configre this?

To recap:

1st T1 will go into FE0/1

2nd T1 will go into WIC-1T

I would still like to load balance and have some redundancy. I am no certin how this i going to affect that.

Thank you.

Paul

pkhatri · ‎03-24-2006

Hi Paul,

This just means that you will need to do a lot more configuration. As I mentioned below, the problem with Ethernet interfaces is that they won't go down even if your link to the ISP goes down. Therefore, you have to use the reliable static routing feature in order to ensure that the route through the interface is brought down when the link goes down.

I've got a sample config that illustrates how to do this (you will need to modify this to apply it to you router):

Replace with an IP that you can ping through your main link - preferably the ISP side of the WAN link address.

interface Ethernet 0/0

description Primary Link

ip address 10.1.1.1 255.0.0.0

!

interface Serial0

description Backup Link

ip address 192.168.1.1 255.0.0.0

!

rtr 1

type echo protocol ipIcmpEcho

timeout 1000

frequency 3

threshold 2

!

rtr schedule 1 life forever start-time now

!

track 100 rtr 1 reachability

!

access list 101 permit icmp any host echo

!

route map LOCAL_POLICY permit 10

set ip next-hop 10.1.1.254

set interface null0

!

ip local policy route-map LOCAL_POLICY

!

ip route 0.0.0.0 0.0.0.0 10.1.1.254 track 100

ip route 0.0.0.0 0.0.0.0 192.168.1.254 254

Have a got at coming up with a config and then post it and I'll have a look...

Pls do rate the post if it helps...

Paresh

warwickconstruction · ‎03-24-2006

Ok Paresh, I will give it a try. COuld you possibly run through your config here and give me some notes on what it all means. I get the general gist of it but some of it my as wll be a foreign tounge!

Thank you so much for all your help so far.

Paul

pkhatri · ‎03-24-2006

Ok, let me try...

The difference here is that you are associating a tracking object with your static route. The static route will remain in the routing table as long as the state of the tracked object stas up. In the config I provided, the tracked object is tracking the status of a RTR object. RTR (which is now called IP SLA) is a mechanism used to initiate QoS-type actions from the router. In this case, I use it to initiate a ping from the router to an address on the internet. The local policy ensures that it is sent out of the ethernet interface. As long as we can ping this address, the RTR object returns a succesful status to the tracked object and the static route stays up. If we can't ping that address, the tracked object and the static route goes down. This provides dynamic tracking of the state of your link.

Hope that explains it somewhat...

Pls do remember to rate the posts.

Paresh

warwickconstruction · ‎03-27-2006

Hello Paresh.

Ok, so far so good. I understand, I think, what you have said so far. Will this configuration be able to take advantage of both links in a load-balance scenario? Or is it limited to primary/backup? I would really like to have both links available....

Paul

warwickconstruction · ‎03-27-2006

Hello again,

I was trying out the rtr commands on my existing setup. I figured I could at least see what it does and how it shows up. Well, I got to the part

track 100 rtr 1 reachability

And my router returned an error. I was in config t and the error was:

router(config)#track 100 rtr 1 reachability

^

% Invalid input detected at '^' marker.

Was I in the correct config mode?

Sorry to be such a pain. I am really trying to get to grips with all this!

Thank you.

Paul

pkhatri · ‎03-27-2006

Hey Paul,

What IOS version are you ruuning ? Some of the commands are IOS-dependent...

Paresh

warwickconstruction · ‎03-28-2006

Hi Paresh,

I am running Version 12.2(8)T5. I guess I need to upgrade it huh?

Thanks,

Paul

pkhatri · ‎03-28-2006

Yes, you do. I believe you need something like 12.3(8)T for the reliable static route feature.

Hope that helps - pls rate the post if it does.

Paresh