Looking for help with 2 1800s, multicast ip over T1

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Jul 28th, 2010
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Hi Folks,

My name's Pete and this is my first post. I have some exposure to Cisco products, mostly tweaking catalysts in a working network to do what the customer wants. I have a new conundrum and I would like to ask assistance. I have 2 Cisco 1800 routers, brand new from the factory routing multicast traffic over a dedicated T1 line. I have my FastEthernet interfaces set up as one one router (I don't have an IP for the 2nd interfaces on either) and on the other, full duplex speed 100, no shutdown. My serial interfaces are setup as T1, AMI, ESF, no shutdown, no IP address. I have one route in each router that looks like ip route serial0/0/0 in one and ip route serial0/1/0 in the other. I can ping the interface I connect my laptop to, and I can ping back from the 1800 to the laptop, I can't ping across the T1. By the way, I have the 2 routers connected locally on my bench using a T1 crossover cable, and my serial interfaces are green (as are ethernet when connected). Any help would be appreciated. Thanks!

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Gregory Camp Wed, 07/28/2010 - 19:15
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Please attach the output of show runn from each router.

Richard Burts Thu, 07/29/2010 - 06:43
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I have looked at your config. The biggest problem is that you do not have an IP address on the serial interface. With no IP address on the interface then the interface will NOT pass any IP traffic. So the first thing that you need to do is to configure an IP address (and subnet) on the serial interface. Make sure that the serial interface of the other router has an IP address in the subnet.

Also in your original post you mention IP addresses on the LAN interfaces that appear to be in the same subnet. It does not work to have the same subnet on LAN interfaces of different routers. So you need to have an IP address of the FastEthernet of the other router that is in its own subnet.



macaroni.duck Thu, 07/29/2010 - 07:43
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Thank you so much for you help, I am now routing! I gave the serial interfaces ip addresses in the same subnet and the FE interfaces addresses in different subnets, and it worked great. All I have to do now is configure my multicast and I'm golden. I'm trying to find that config somewhere out there.

Gregory Camp Sun, 08/01/2010 - 17:24
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Here is a good getting started guide for multicast


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