Routing subnets

[controlfreek]

I have a small site which has a 3640 router that services 8 different subnets with the local lan configured as 192.168.80.0. I have DHCP running on the 3640 side of the network. I have another location using the same subnet 192.168.80.0 that I need to connect to this 3640 via a 1751 router over a t1. Do I need anything other than IP forwarding?

[gauravprakash]

i guess u can make the 1751 as dhcp relay agent, which can give IPs to remote site

[controlfreek]

I was told that I might need bridging on the 3640 in order to communicate to the 1751 because they have the same subnet? Someone else told me to just use IP Forwarding and routing.

[mhussein]

Bridging is an option, although not recommended specially if you have a large number of hosts on the remote site. The volume of the extended LAN broadcasts may saturate the T1 link.

Another option is to use NAT, check this document on how to configure NAT in overlapping networks:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a0080093f30.shtml

However, NAT introduces other problems as well, such as DNS and NetBIOS name resolution.

You can use bridging or NAT temporarily, but you should consider renumbering the ip addresses on the remote site. You can start by assigning a secondary ip address/subnet to the remote site's LAN interface and gradually switch hosts over to the secondary subnet and gateway.

Regards,

Mustafa

[joyride_us]

Hi,

either the addresses are not overlapping and Bridging is a good option (use VLAN or other technics to define broadast domains), or they are overlapping and NAT is a good solution!

Good luck!

[rstanaford]

Regarding Mustafa's post concerning DNS resolution... This is a good read. It might be overkill for this particular situation involving two small overlapping networks, but it might provide inspiration.

Good luck to you,

-Richard

Enabling Enterprise Multihoming With Cisco NAT..

http://www.cisco.com/warp/public/cc/pd/iosw/ioft/ionetn/tech/emios_wp.htm