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Point to Point

I have 2 new T1 circiuts installed for a point to point connection between two offices. I have not worked with a cisco router in quite some time.

The topology I have now:

Office 1 network = 192.168.100.0

Office 2 network = 192.168.200.0

2*T1 = 3.0Mbps Point to Point

Here is my current configuration that I have setup so far:

Office one

Fast Ethernet0/0 IP = 192.168.100.250

Serial0/0/0 Unassigned

Serial0/10/ Unassigned

IP default-network 192.168.100.0

Office 2

Fast Ethernet0/0 IP = 192.168.200.250

Serial0/0/0 Unassigned

Serial0/10/ Unassigned

IP default-network 192.168.200.0

IP Route

I added this routing:

Ip Route 192.168.200.0 255.255.255.0 192.168.200.250

IP Route 0.0.0.0 0.0.0.0 192.168.200.250

If I run command 'show ip route' I get this: "Gateway of last resort is not set"

What are the steps I should take to get this point to point operational ultilizing the 3.0Mbps for it.

17 REPLIES
Hall of Fame Super Silver

Re: Point to Point

Ed

I would say that the first thing that you need to do is to assign IP addresses to the serial links. Without IP addresses on the interface the router can not forward IP packets over the interfaces.

You might also think about whether you want to operate the T1s independently with each one having its own IP address or whether you want to combine the T1s with PPP multilink (which would assure more equal utilization of both links).

Also the default-network commands are not needed and are not working as you show them. (default network 192.168.100.0 on the router with that subnet as a local subnet does not do much)

And the ip route statements that you give are problematic. You do not need a static route for a network or subnet that is locally connected on the router since the local networks or subnets will automatically be put into the routing table.

And the default route that you give will not work. In effect you are saying that to forward a packet for an unknown destination you should forward it to your own router interface. But you really need to forward it to an interface on some other router.

What you need to do after you assign IP addresses to the serial links is to decide whether you will use static routes or use some dynamic routing protocol. If you are going to use static routes then the office with 192.168.100.0 needs a static route saying:

ip route 192.168.200.0 255.255.255.0

and the other office needs a static route with the addresses inverted.

Then you need to think about whether you need a default route. If the network is really just these 2 offices and the serial links between them then you do not need a default route. If one or both of the offices do connect to something else (or to the Internet) then you may need a default route.

HTH

Rick

New Member

Re: Point to Point

What routing protocol are you running in your router?

In your case, I would try it like this:

Office 1:

Serial0/0: 10.100.100.254 255.255.255.252

FastEthernet: 192.168.100.250 255.255.255.0

Router EIGRP 250 (assuming you're running EIGRP)

network 10.0.0.0

network 192.168.100.0

ip route 0.0.0.0 0.0.0.0 10.100.100.253

Office 2

Serial0/0: 10.100.100.253 255.255.255.252

FastEthernet: 192.168.200.250 255.255.255.0

Router EIGRP 250

network 10.0.0.0

network 192.168.200.0

ip route 0.0.0.0 0.0.0.0 10.100.100.254

hieu

New Member

Re: Point to Point

OK so this is what I have now in office A

FastEthernet0/0 192.168.100.250 Yes NVRAM UP UP

FastEthernet0/1 Unassigned Yes NVRAM administratively down down

Serial0/0/0 unassigned yes NVRAM down down

Serial0/1/0 unassigned yes NVRAM administratively down down

Multilink1 10.100.100.254 yes NVRAM down down

I created the Multilink1 and added the 2 serial ports to it. i assumming that this is the correct thing to do.

Hall of Fame Super Silver

Re: Point to Point

Ed

I believe that creating the multilink and assigning an IP to the multilink was a good thing to do. I notice that serial0/1/0 is administratively shut down and that serial0/0/0 is down/down. You should do a no shut on serial0/1/0 and you should investigate why serial 0/0/0 is down/down and resolve this.

Perhaps we might offer more help if you would post the config of one or both of the routers.

HTH

Rick

New Member

Re: Point to Point

yeah I did a no shut on both but have the same thing. Both show down now. Would the router in my other office not being connected have anything to do with the down?

Hall of Fame Super Silver

Re: Point to Point

Ed

It depends a bit on how they are connected. If they are connected on a private serial (T1 or partial T1) where you provide the clocking then the other end being not connected would certainly keep this end down. Can you tell us anything about how they are connected?

HTH

Rick

New Member

Re: Point to Point

This connection is a private. I kind of figured that would be why it was down.

Hall of Fame Super Silver

Re: Point to Point

Ed

That seems reasonable. Let us know what happens when you get both ends started.

HTH

Rick

New Member

Re: Point to Point

I configured both routers as presented by hcao asbove, however both are showing down. Is there a command I have to issue to enable multiplexing in a 1841 router? I am also checking with the PTP provider to see if there a configuration that needs to be changed.

Hall of Fame Super Silver

Re: Point to Point

Ed

There are a couple of things about the config suggested by hieu that I think that you should be careful about.

1) his config only activates one serial link (using the default HDLC encapsulation). It was my understanding that you want to use 2 serial links between offices. You could follow his direction and configure an IP subnet on each serial interface to make use of the second serial interface. Note that this will have an impact on the static routes that he suggested. You can also utilize both serial links by using ppp multilink as discussed in a previous post in this thread.

2) hieu has a default route in each office pointing to the other office. If the 2 offices are all there is to the network (as seems to be the case from what we know so far) then no default route is needed. If there is more to the network then probably one office needs the default route as shown. But the other office needs to have its default route point to the other part of the network.

The fact that the serial interfaces still are down suggests that there may be more than a configuration issue. Perhaps you can post the output of show interface and also post the configuration of the routers. If we see what is really going on then perhaps we can make better suggestions.

HTH

Rick

New Member

Re: Point to Point

You can mirror the config above for the second t1 for the serial interface (assign a different ip, of course). EIGRP will do load-balance per-destination on your serial links by default if they've the same cost (I assume it is, don't know for sure until you post your config and show ip eigrp topo.

do a show controller t1. are they all up ?

As Rick had suggested, please post your router config, and we do what we can to help you. Rick is an outstanding resource in this forum, and I've learned quite a bit from him by following various threads of different topics.

good luck

hieu

New Member

Re: Point to Point

OK I have attached 2 .txt files of the configuration. Any ideas would greatly appreciated.

New Member

Re: Point to Point

Here's a good link for multilink p-2-p sample.

http://www.cisco.com/univercd/cc/td/doc/product/aggr/10000/10ksw/mlppos.htm

please post the config of both remote and local routers. are the t1 controllers shown as up?

hieu

Hall of Fame Super Silver

Re: Point to Point

Ed

I have looked at what you posted and I have one observation: the fact that you have configured ppp authentication chap on both serial interfaces but have not configured anything to help authenticate is keeping the serial interfaces down. Remove the ppp authentication chap from both serial interfaces (and from the serial interfaces on the other end if it is configured there) and let us know what happens.

HTH

Rick

New Member

Re: Point to Point

OK I have removed the PPP Authentication Chap on all serial interfaces. However this did not bring up the serial or multilink1 connections. I also removed the routes I added earlier to see if that would do it and that did not work. Now one thing that came to my mind, since this is a private line connection, don't I need to designate clocking on one of my routers?

Hall of Fame Super Silver

Re: Point to Point

Ed

It is quite possible that you do need to designate clocking on one of the routers. If the provider is not providing clocking, and you do not designate clocking then it would cause a problem. But the symptoms would be slightly different. If it were a clocking issue I would expect the interface status to be up/down. Your post indicates that the interfaces are down/down if I understand them correctly. In my experience down/down suggests a different problem, frequently it is a physical layer problem such as disconnected cable, faulty cable, powered off CSU/DSU, or something like that.

I do note that the show interface output that you posted indicates that the router has integrated CSU/DSU and I do not see any controller configuration or service module configuration. Configuring the CSU/DSU might be helpful in this issue.

HTH

Rick

New Member

Re: Point to Point

OK, did loopback test on the CSU/DSU units and they are functioning correctly. Also was in contact with my service provider and the private line is working. However, I need to get the demarc extension verified so I will let you know. A cisco engineer says that the config should be fine so as soon as I get my indor cable verified and will let you know the outcome. I real appreciate all your help guys.

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