Cisco Router – Running PPPoE and dot1Q Protocol Simultaneously

ciscooptical;routerswitchtrunk

So here's a problem I need to solve and I am having issues researching for an answer.

I have an optical cable that's coming in through SFP and it is forced to be connected to a switch before going to the router. This link is actually a trunk and it holds a few VLANs. The problem is, the switch will take this link and connect to the router with PPPoE, and then the router will have a connection going back into the switch with dot1Q (for VLANs).

So the current scenario is this:

Switch receives an optical trunk link, switch is connected to router (PPPoE), router connects back to switch (dot1Q) in order to distribute to the rest of the network.

So is it possible? If I am not mistaken, the router on hand is the Cisco 1800 router.

And if this is not possible, any suggestions on how to deal with this? The router is not able to take the optical trunk link, which is why this whole problem is created.

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Best Answer

Now that your question is a bit more clear, you con connect the switch to the router on one of the copper interfaces. Just configure the link between the router and the switch as a trunk link. If you need PPPoE on one of the VLANs, then set up PPPoE on the subinterface for that VLAN. Just don't run your internal VLANs out to the ISP.

The drawing is a pretty poor way of doing things because you have no firewall, and your network equipment is exposed to the public Internet.

Just because the ISP connects to your switch via fiber, that does not mean that your switch must connect to the router via fiber. The switch really doesn't care which interface is connected to either the ISP, the router, or the hosts. As far as the switch is concerned, the router is just another host, but one connected via a trunk, and you can run a trunk on any of the switch interfaces, as long as the device on the other end of the link understands VLAN tags.

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