OSPF routing protocol is CCNP study focused curriculum in SP CCIE and EI CCIE exam also related to assessment content, but also often encounter network in an interview workers in OSPF interview questions. So learn OSPF is very important.
Most know H UB-Spoke structure is the most common WAN design one, and today we will discuss at the Hub-Spoke environment deployments OSPF is pay attention.
First OSPF is a link-state protocol, the most important feature is the link-state protocol within the same area all router database the same database, that is, when the other one S Poke time jitter routing, it will first issue H UB side, and then by the H UB end to all the S Poke end . That is, when a site appears route flapping, all the sites will be affected , so the H UB-Spoke environment, the deployment of OSPF 's main job is to reduce flooding. So how to reduce the flood of it? The answer is zoned area, and are aggregated and filtered . As shown:
Small scale network, H UB and S Poke can be placed in the same area, medium-sized, can make S Poke dividing the same in the region . If there are a large number of sites, at H UB end router hardware resource functions ( the CPU and memory ) sufficient in the case, each S Poke dividing a region .
Division of regional issues we reached a consensus, then the next a question is ABR 's position . What meaning , that is, ABR in the end placement is H UB on, or S Poke on . As illustrated :
FIG first of ABR in H UB on, H UB received S Poke specific routes end, then H UB on can S Poke sent detailed aggregated routing or filtering , or the use of a special area, hair transmitting summary route or default route to other areas, which is the other S Poke on . When S Poke site where route flapping time, the route is transmitted will impact S Poke to H UB end of this link, H UB internal site and the other endS Poke site internal network will not be affected.
The second map is ABR each S Poke on, S Poke and H UB between a Area 0 , each S Poke internal site is a separate area, each S Poke on site internal routing summarize and sent to Area 0 . If the site internally generated flip phenomenon, the route passes only affect the interior of each site, but due to issue H UB end is a summary route, so there may be some unnecessary traffic bandwidth is wasted. Summary at :
L the ABR placed in H UB on , summary or filter point H UB on the LSA 's information H UB and S Poke transmitted on the link between a plurality, but for less waste of bandwidth;
L the ABR placed in S Poke , the summary or filter point S Poke on the LSA transfer less, but may be wasted H UB-the Spoke bandwidth is between more.
The next issue to discuss is H UB and S Poke configured OSPF network type used . We all know that DM V # P # N is H UB-Spoke environment can deploy the optimal one solution, there are three stages in stage three times, Spoke next hop routing in H UB or S Poke on it does not matter, but we can discuss the difference between various types of network interfaces at the time of deployment , as follows:
This can choose according to their own needs, recommend the use of personal P2MP + BFD 's way.
These are the Hub -Spoke environment deploy OSPF when discussed . In fact there is convergence and other considerations . We will IELAB of EI CCIE -depth analysis of further courses in.