Contents
Why we need Ibgp when we have IGP?
BGP (iBGP, EBGP) allow for peering sessions to be established between devices that are multiple hops away. iBGP advertises those global prefixes within the AS to other edge routers because IGPs are not designed to scale to handle the number of global internet prefixes that exist in the global internet routing table.
What is the function of Ibgp?
The purpose of IBGP is to provide a means by which EBGP route advertisements can be forwarded throughout the network. In theory, to accomplish this task you could redistribute all of your EBGP routes into an interior gateway protocol (IGP), such as OSPF or IS-IS.
What is the main difference between iBGP and eBGP?
The main difference between iBGP and eBGP peering is in the way routes that were received from one peer are propagated to other peers. For instance, new routes learned from an eBGP peer are typically redistributed to all iBGP peers as well as all other eBGP peers (if transit mode is enabled on the router).
What is the IGP?
An interior gateway protocol (IGP) is a type of routing protocol used for exchanging routing table information between gateways (commonly routers) within an autonomous system (for example, a system of corporate local area networks). This routing information can then be used to route network-layer protocols like IP.
What happens if iBGP is used as an IGP?
If IBGP is used as an IGP, this presents severe scaling problems; every router would have to peer with every other router on the network. The full-mesh requirement can be overcome by carefully designating intermediate routers as route reflectors, but we’re still left with the issue of excessive route recursion.
What makes a BGP session an internal iBGP session?
A BGP session between two BGP peers is said to be an internal BGP (iBGP) session if the BGP peers are in the same autonomous systems. By default, the peer relationship is established using the IP address of the interface closest to the peer router.
Is the BGP protocol the same as the IGP protocol?
BGP is a routing protocol, but it is not an IGP but an EGP. So it does not handle routes within the same AS, it is only for exchanging routing information between different ASn. Routing within the same AS must be handled differently. iBGP requires full mesh of iBGP routers.
How is the peer relationship established in iBGP?
By default, the peer relationship is established using the IP address of the interface closest to the peer router. However, using the neighbor update-source ( registered customers only) command, any operational interface, including the loopback interface, can be specified to be used for establishing TCP connections.