Now that you have gained a basic understanding of ospf and bgp, you may want to know when and how to choose from or apply them? On the one hand, if you are conducting internal routing, such as routing within a site, company, or campus, you will want to use OSPF as it is used for internal network routing. This would typically work between switches and routers in the same location. On the other hand, if you are looking at building in-site with multiple homes, you might want to consider BGP.
OSPF is based on Dijkstra's algorithm for finding shortest paths between two points. Basically, OSPF works on the concept of "areas. This allows each device to determine the best next hop for any particular destination. This full view does come with some downsides: greater memory and CPU resources being used.
That's why OSPF is usually used for internal, rather than external, routing. Being an IGP, the overhead of being a link-state protocol is minimized due to the smaller topology. Not to say they cannot get large but compared to the topology of internet routing, they are usually minimal. The benefit to being a link-state protocol is its ability to highly engineer traffic routing due to its in-depth understanding of the topology.
Each router has a full view of how each router is connected. The downside is that many convergence scenarios require a full or partial table recalculation. Today's routers and switches are usually insulated from this, but it does kick off a lot of work.
Imagine if a full table needed to be calculated every time a new dynamic internet routing node was brought online. That scenario could cause some issues and is why OSPF is not suitable for internet routing. Not to be confused with the "Exterior Gateway Protocol" which was the protocol used prior to BGP for internet routing. Protocols such as BGP are typically used for external network routing at the edge of your network.
Where your network interfaces with another provider is typically where an EGP gets implemented. BGP is sometimes classified as a distance vector protocol but, in reality, it is a path vector protocol. In contrast to link-state, which knows what the entire network looks like, distance vector learns paths. This would be very useful for us who don't work in the field.
I am sitting at this point in my GNS3 configuration, but I am not sure how to design this part of the network to make it realistic as possible.
Would really appreciate some practical configuration examples, and I am pretty sure this would help the OP better, as I am sure this is exactly what he is experiencing as well. Edit: I have just pulled a CCIE book i bought for studying, which I am yet to read, and this is where all the neat stuff is such as summarizing, advertising default routes etc, but it looks like it is based on CE rather than PE. Haven't been here for a while, but nice to see the discussion went on.
Thanks for all the answer so far! Because there is no use of BGP there. If you encounter a technical issue on the site, please open a support case. Communities: Chinese Japanese Korean. All Rights Reserved. The Cisco Learning Network. Enterprise Certifications Community. View This Post. July 2, at PM. Hi Frank its more with how BGP works i guess.
But what about coding? In path vector routing the router has the list of networks which can be reached with the path to reach each of them. The BGP protocol does not have any information about what is happening inside an autonomous system and that a necessary prerequisite for an autonomous system.
It has its own internal topology and chooses the routing protocols to determine the routes. It is named as Border Gateway Protocol because in this a BGP router must communicate with a peer in another autonomous system usually which reside near the edge border of the autonomous system. This communication occurs when a pair of autonomous systems accepts to exchange the routing information and which involves the routers to become the BGP peers.
The OSPF is based on the link state routing where each router sends the state of the neighbour router to every router present in the area. On the other hand, BGP is based on path vector routing where a router has a list of networks that can be reached with the path to reach each of them.
Your email address will not be published. OSPF is an Interior gateway routing protocol in which the routing operation is performed inside an autonomous system. On the other hand, the BGP is an Exterior gateway routing protocol which enables the routing operations to be performed between the two autonomous systems.
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