![]() ![]() The University provides the following notification of grade profiles and degree programme places to enable prospective applicants to make informed choices in their application for admission to NUS undergraduate degree programmes. BGP route to 4.0.0.Notification of Grade Profiles and Degree Programme Places for Singapore-Cambridge GCE A-Level and Local Polytechnic Diploma Applicants for the Academic Year 2023/2024 NUS Undergraduate Admissions Exercise iBGP gives you the ability to know (at R2) which way to go to take the shortest BGP path. Some may be preferred out R3 (via AS7660). However, not all routes will be preferred via AS3356 (attached to R1). ![]() In this case, BGP chose this because this route has the shortest AS Path list. In this case, BGP chose to go to 4.0.0.0/9 via 4.69.184.193 (notice the best under the RIB entry). To understand why you might want iBGP, consider this routing entry to 4.2.2.2. Countermeasures have now been implemented in IGP protocols ( like this one for OSPF in IOS) to prevent redistribution from BGP into OSPF from causing a major outage. There have been some notorious instances where a Tier-1 ISP accidentally redistributed their BGP table into their IGP (even when the internet table was a small fraction of its current size) and it caused major outages.Name any other IGP (EIGRP, RIPv1/2, IS-IS, IGRP) and the same story is true. Using the example of OSPF, the LSA processing / flooding requirements from 500,000 routes uses too many resources in your routers. if you try to use OSPF for this purpose, it will break your network. OSPF was not designed to handle many thousands of routes in internet BGP tables.You use BGP because you don't want to carry your entire internet routing table in your IGP (i.e.these make BGP an attractive way to implement custom routing policies within your own autonomous system (by using iBGP).Īs with everything there are trade offs the scalability, control, and flexibility you get from iBGP means that it's a slower converging protocol than IGPs (in general). Thus, iBGP is required unless you're willing to redistribute all the routes you've learned via eBGPĮnforce boundaries of trust / control: BGP has more ways to filter peers than IGPs (for controlling what you advertise and receive).įlexible data structures (somewhat related to the previous bullet): BGP communities, BGP Extended communities, local-pref, etc. BGP can handle many more routes than IGP protocols. Scalability 1: Imagine that you're receiving 500,000 EBGP routes in more than one location 2, and you need to influence the per route exit point in your AS. Can anyone explain me what is the need of IBGP communication for the routes, when we have the IGP protocols (OSPF, RIP) for internal communication?
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