How to configure Router as Switch

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Oct 13th, 2007
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In my scnario, I have take bandwidth from upstream provider and I have to distribute the bandwidth through DSLAM (Broadband).

I have a Cisco 2821 router between Upstream provider and DSLAM, but the service provider has given me 126 Public IPs which include the IPs of gateway and other equipment at service provider side. I have to give public IPs to my customers from the same subnet.

How to configure same subnet of IPs to both the sides of router or is there any method we can configure both the interface of the router as a switch? which solves my purpose.



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nambi_gct Sun, 10/14/2007 - 23:46
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Please check IRB feature and I hope this will help you.

stephenamstutz Mon, 10/15/2007 - 08:21
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You need to bridge the interfaces as opposed to routing across them. Use the following;


bridge irb

interface FastEthernet0/0

no ip address

bridge-group 1


interface Dialer0

no ip address

bridge-group 1


interface BVI1

ip address


bridge 1 protocol ieee

bridge 1 route ip


You can then use the public IP addresses on the inside of your router.


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