Michael,
BGP is a huge topic...I'm surprised they have you studying that for CCENT. But, in a nutshell the ASN determines what type of BGP it is. The same number between two peers means it's iBGP, and different ASN's means it's eBGP. The ASN is used for things such as loop prevention. By default, although it can be changed, a BGP router will drop traffic if it sees its own AS in the path. BGP uses something called AS Path and it represents the ASes that he prefix was learned from and the path it took to get to the router you're lookign at.
RIP1 and Ripv2 are both restricted to 15 hops. After that, the route is deemed dead. Ripv2 will send a mask to it's neighbors, but Ripv1 will not. That means that Rip1 will only see classful networks. Ripv2 can use vlsm because of it sending a mask.
EIGRP and OSPF are much better for larger networks. OSPF can be divided into areas and is a standard protocol meaning different vendors can use it. When you have a mix of Cisco and other vendors, like Dell, you can use OSPF to exchange routing information. EIGRP on the other hand is Cisco proprietary and only works between Cisco devices. EIGRP is based off of IGRP, but IGRP is no longer in existence and I doubt you'll ever see it.
HTH,
John
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HTH,
John
*** Please rate all useful posts ***
