4. Consider the network shown below. Suppose AS3 and AS2 are running OSPF for their intra-AS routing protocol. Suppose AS1 and AS4 are running RIP for their intra-AS routing protocol. Suppose eBGP and iBGP are used for the inter-AS routing protocol. Initially suppose there is no physical link between AS:2 and AS4. 4b 4c 4a 3c AS4 2c ?? 3b 2a 1c 2b 1b AS3 1a AS2 1d AS1 a. Router 4c learns about prefix x from which routing protocol: OSPF, RIP, eBGP, or iBGP? b. Router 3b learns about x from which routing protocol? c. Router 1a learns about x from which routing protocol? d. Router 1c learns about x from which routing protocol