title: Computer Networking - BGP
body: <p>Consider the network shown above. Suppose all ASs are running OSPF for their intra-AS routing protocol, with the cost of each link equal to 1. Suppose eBGP and iBGP are used for the inter-AS routing protocol. Initially suppose there is no physical link between AS2 and AS4.</p>
  
  <p><img src="https://i.stack.imgur.com/RTTWa.png" alt="enter image description here"></p>
  
  <p>Routers(1a,1b,1c,1d,2a,2b,2c,3a,3b,3c,4a,4b,4c) learns about prefix x from which routing protocol: OSPF, RIP, eBGP or iBGP?</p>
  
  <p>I'm so confused on BGP, I think the answers should be either eBGP or iBGP. Can anyone help me with this and explain why? 
  (I think 1c and 3c should be eBGP, and 3a and 1d should be iBGP. Not sure about others)</p>