Re: Configuring new serial int

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 · ‎03-21-2006

Hi Paul,

A WIC-1T gives you a serial interface. You can use a config like the following at each end:

interface serial0/0

ip address x.x.x.x y.y.y.y

encapsulation ppp

If this is a point-to-point link, the above should get you going.

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

Paresh

warwickconstruction · ‎03-21-2006

Thanks for your reply Paresh. I don't have access to the Adtran to configure it so I guess I will need to ask the ISP for config details. The Serial int will be going to a v.35 on the adtran. I was told by the tech that the encpsulation would be hdlc. Does that sound right?

pkhatri · ‎03-21-2006

You don't really need access to the Adtran as long as you know details of the service.

HDLC is fine - just remove the 'encapsulation ppp' command from the config I provided earlier.

Pls do remember to rate posts that help.

Paresh

warwickconstruction · ‎03-22-2006

Once again, Thank you for your help. I have a few more questions. I asked previously in this forum about load balancing and you replied telling me bout CEF and showed me a config that was something like this:

ip cef

!

ip route 0.0.0.0 0.0.0.0 serial0:1

ip route 0.0.0.0 0.0.0.0 serial1:1

There is alredy a route in the router that is like this:

ip route 0.0.0.0 0.0.0.0 xx.xx.xx.xx (where xx is the ip address of the default gateway of the ISP)

There is also this:

ip nat inside source static 10.0.0.2 xx.xx.xx.xx

(where the 10.x.x.x address is the outside nic on the ISA server the router is connected to and xx is the outside interface of the router, connected to the adtran)

Is this going to be affected by the new configuration? If so, ow should I reconfigure the router?

Again, any help would be apprciated. I realise the router is probably not configured very well and I am happy to make changes for the better, but it works right now and I am loath to break it!

Thank you.

Paul

pkhatri · ‎03-22-2006

Hi Paul,

Here's what you need to do:

- add another default route with next-hop equal to the ISP's address on the second link:

ip route 0.0.0.0 0.0.0.0 yy.yy.yy.yy

- the inside source static command is fine and can stay

- if you have an 'ip nat inside source list' command, you will need to replace it with something like the following:

ip nat inside source route-map ISP1-map interface serial0:1

ip nat inside source route-map ISP2-map interface serial1:1

!

route-map ISP11-map permit 10

match interface serial0:1

!

route-map ISP12-map permit 10

match interface serial1:1

You might wanna post your full config in order so that it helps us to see if we have everything covered, though...

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

Paresh

warwickconstruction · ‎03-22-2006

Hi again Paresh,

I have attatched my full config as suggested. Any suggestions regarding improvments will be greatfully received.

Thank you.

Paul

pkhatri · ‎03-22-2006

Just another query before I comment on the config ... Both your DSU facing interfaces will end up being serial interfaces, right ?

Paresh

warwickconstruction · ‎03-22-2006

Yes Paresh, they will both be WIC-1Ts.

Thanks,

Paul

pkhatri · ‎03-22-2006

In that case, Paul, the changes I mentioned earlier should be all you need in order to get this working over the two link.

Feel free to post back with the complete config once you have done it up if you want us to give it a look.

Paresh

warwickconstruction · ‎03-22-2006

Hi again Paresh,

Ok, I am just a bit confused about one point. With the lines

ip nat inside source route-map ISP1-map interface serial0:1

ip nat inside source route-map ISP2-map interface serial1:1

Is the number after the : indicating the int number or is it in addition to the int number. My serial int is numbered serial0/0. So, once that is gone and the two new serial ints are installed would the line look like this?

ip nat inside source route-map ISP1-map interface serial0/0:1

ip nat inside source route-map ISP2-map interface serial0/1:1

Do I also still need the following:

ip cef

!

ip route 0.0.0.0 0.0.0.0 serial0/0:1

ip route 0.0.0.0 0.0.0.0 serial0/1:1

and with what I just said above, would they look like that?

Last of all (for now!)

Would I be able to configure something like this using wht I have installed right now? Obviously, it would not completely work because the serial int I have is not connected to anything. But would it not act like the link was there but not availible?(I have it cable loop backed)

If so, would it look like this?

ip cef

!

ip route 0.0.0.0 0.0.0.0 Fastethernet0/1:1

ip route 0.0.0.0 0.0.0.0 serial0/0:1

And then

ip nat inside source route-map ISP1-map interface Fastethernet0/1:1

ip nat inside source route-map ISP2-map interface serial0/0:1

!

route-map ISP11-map permit 10

match interface Fastethernet0/1:1

!

route-map ISP12-map permit 10

match interface serial0/0:1

Would that work? Even just to help me see how it comes together or am I way off base?

Thank you again.

Paul

pkhatri · ‎03-22-2006

Hmm.. I see I've got you a bit confused. What I posted was an example and as such, used some sample interface types.

So addressing your questions:

- the number after the colon is the channel-group number; that is something you use with E1/T1 channelised interfaces. In your case, you are using serial interfaces so you will not need that at all. So pls remove the colon and the following number from your config !

Your config lines will look like:

ip nat inside source route-map ISP1-map interface serial0/0

ip nat inside source route-map ISP2-map interface serial0/1

You still need the following:

ip cef

!

ip route 0.0.0.0 0.0.0.0 serial0/0

ip route 0.0.0.0 0.0.0.0 serial0/1

In answer to your last question, it's best not to configure the above if the link is not up. In fact, things get a lot hairier with Ethernet interfaces cause they don't necessarily go down when the link goes down. So I would not recommend using this with your current setup. Install the 2 T1s first and then tweak your config to get the redundancy working.

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

Paresh

warwickconstruction · ‎03-22-2006

Ok, last question for now, I promise!

I understand that I will have 4 routes configured.

The two for the serial interfaces and two for the ISP hops:

ip route 0.0.0.0 0.0.0.0 serial0/0

ip route 0.0.0.0 0.0.0.0 serial0/1

ip route 0.0.0.0 0.0.0.0 yy.yy.yy.yy

with the yy being whatever the next hop is for the ISP? Do I have that right?

I am learning a great deal, thanks once more.

Paul

pkhatri · ‎03-22-2006

No probs at all, Paul.

You only need to have two routes configured.. either the first two or the last two of the 4 that you posted - it does not really matter which but I would suggest that you use the ones pointing to the serial interface - that gives you some protection in case your change your IPs at some point:

ip route 0.0.0.0 0.0.0.0 serial0/0

ip route 0.0.0.0 0.0.0.0 serial0/1

Paresh

warwickconstruction · ‎03-22-2006

Once again, thank you for your help. Do I understand corrctly, that I could immplement that right now?

Instead of the route

ip route 0.0.0.0 0.0.0.0 xx.xx.xx.xx

I could have it point to the FE0/1 int? If this is the case, is there anything else I would need to do?

Paul