I was woundering if it recommended/possible to peer with multiple providers with only one port on a router. Currently we have a layer 2 switch that connects to various ISP's, Is it possible to connect each peer to the switch which then connects into the BGP routers which peer with just the one interface. I guess this is probabily possible with a dot1q router on a stick type configuration however it seems a kind of wierd for this situation.
From my very limited knowledge of bgp i though you would need a too use a new interface with each ISP you peered with.
You basically have the idea correct. It would be possible if the port on the router you are connecting to is a trunk port connected to your switch. Each ISP should be on its own VLAN. The "new interface" for each ISP would be the VLAN interface created/assigned for each ISP.
You are correct that it is an odd setup as it has a single point of failure and typically a company is deploying BGP to create redundancy.
Yes, you can peer with multiple ISPs on the same physical interface.
This is encouraged at large carrier neutral data centers (e.g. Equinix, CoreSite, etc) where they provide a peering fabric. There, you can connect to multiple ISPs with a single connections.
The downside of what you are suggesting is that if the switch fails, you lose all of your connections. Suggest that you use a dedicated port per uplink carrier. Also, consider multiple modules and balance the carriers over the modules.