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Routing internet traffic from a specific VLAN at a remote site through a PTP to HQ site and out to the internet


I recently inhereted a partially completed project from another engineer which I need to finish but can't quite figure out how to accomplish properly.

The setup goes like this...

I have two sites, Berk (The HQ Office) and Sac (The Remote Office). Each site has multiple VLANs defined within each site's core Cisco 3750G switches running IPBASE ver 12.2(25r)SEE4.

There is a PTP connection between the core switches iBerk and Sac. I am using Layer 3 switching in both locations with RIP v2 running to propagate the routes.

I would like to route internet bound traffic originating only from VLAN 12 ( at my Sac/Remote Office location through the PTP interface on my core switch to the Berk/HQ Office's core switch and then to the internet via the defualt route to my ISP at my Berk location. The previous engineer working on this project set the default gateway of nodes on VLAN 12 (in Sac) to be the ip address of the Berk 3750G PTP IP Interface Address. See configs attached.

Using this configuration, traffic on VLAN 12 in Sac still goes out via the default route in Sac instead of the default route in Berk via the PTP. A trace route from VLAN 12 in Sac to an internet IP shows it flowing to the Sac core switch, and then egress to the Sac default route IP.

I'm not certain if I am using the wrong IP for the default gateway to accomplish what I am looking to do or if I have failed to properly configure all the necessary routing. I did consider using Policy-Based Routing to accmoplish this but I am not certain it will do what I need it to.

Any advice would be greatly appreciated.


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Routing internet traffic from a specific VLAN at a remote site t

Hello Zane,

you need PBR on remote site sac matching on source address of VLAN12 of SAC site.

this should be supported on your C3750. Eventually it may require an SDM template change that requires a reload if so you need a maintenance time window.

However on Berk site the NAT configuration of the internet facing router has to be changed in order to translate also SAC vlan 12 ip subnet

It is not clear if Berk facing internet router is under your control or not.

In any case NAT is NOT supported on your multilayer switches so you can accomplish your design target only if you have internet facing routers on the two sites and you have control of them

Hope to help


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