BGP options on Internet

Single homed site

  • a site with a single connetion to ISP is called single homed
  • either use static routes, or advertise the site routes to the ISP and receive default route from ISP
  • when customer is connected to SP via static routes, traffic from that customer on Internet is indistinguishable from traffic from the ISP – you are not ISP independent
  • in this environment it is not recommended to run BGP

Dual homed site

  • customer connect again to one SP but via two links on one router or two links on two routes or single link on two routers to the ISP.
  • it brings more redundancy
  • same as single homed site, i.e. you can use static routes or advertise routes to ISP
  • in this environment it is not recommended to run BGP

Multi-homed site

  • customer is connected to two ISP.
  • this gives you ISP independed solution – you run BGP, you got AS number, you can route your public networks via whatever ISP you choose, you can manipulate the routes however you want
  • in this scenario bgp is typically used. You can manipulate the path, do some path manipulation what networks are reachable via what ISP.
  • You can exchange with ISP whole routing table of just some networks (ISP own networks or networks to some known ASses you want to reach)

Dual multi-homed site

  • same as multi-homed just with another redundant link to ISPs

 Route reception options

  • default routes from SP
  • some routes + default routes
  • all routes