When you're preparing to transfer the BSCI communicating and acquire your CCNP certification, digit of the large challenges is acquisition BGP. BGP is totally assorted from some prescript you scholarly to acquire your CCNA certification, and digit of the differences is that BGP uses line attributes to souvenir digit line over added when binary paths to or from a instruction exist.
Notice I said o or from. In early liberated BGP tutorials, I discussed the BGP attributes weight and local preference. These attributes are utilised to souvenir digit line to a instruction over another; for example, if BGP AS 100 has digit paths to a instruction in AS 200, these digit attributes crapper be ordered in AS 100 to souvenir digit line over another. But what if AS 100 wants to inform the routers in AS 200 as to which line it should ingest to accomplish a presented instruction in AS 100?
That's where the BGP concept Multi-Exit Discriminator, or MED, comes in. The MED continuance crapper be ordered in AS 100 to verify AS 200 which line it should ingest to accomplish a presented meshwork in AS 100.
As with some BGP attributes, the MED crapper be ordered with a route-map. What you requirement to check is that there is no set med continuance in line maps. To modify the MED of a path, you requirement to modify the amount of that path. Let's feature that there are digit entry paths for AS 200 to ingest to accomplish destinations in AS 100. You poverty AS 200 to ingest the 100.1.1.0/24 line over the 100.2.2.0/24 path. First, refer the digit paths with digit removed ACLs.
R1(config)#access-list 22 accept 100.1.1.0 0.0.0.255
R1(config)#access-list 23 accept 100.2.2.0 0.0.0.255
Next, indite a route-map that assigns a modify amount to the more-desirable path.
R1(config)#route-map PREFERPATH accept 10
R1(config-route-map)#match ip come 22
R1(config-route-map)#set amount 100
R1(config-route-map)#route-map PREFERPATH accept 20
R1(config-route-map)#match ip come 23
R1(config-route-map)#set amount 250
Finally, administer the route-map to the edge or neighbors.
R1(config-route-map)#router bgp 100
R1(config-router)#neighbor 22.2.2.2 route-map PREFERPATH out
The key points to ready in nous is that patch some BGP attributes favour a higher value, the MED is essentially an outside amount - and a modify amount is preferred, meet as with the protocols you've already unnatural to acquire your CCNA certification.
Chris Bryant, CCIE #12933, is the someone of The Bryant Advantage, bag of liberated CCNP and CCNA tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages.
For a FREE double of his stylish e-books, How To Pass The CCNA and How To Pass The CCNP, meet meet the website! You crapper also intend FREE CCNA and CCNP communicating questions every day! Pass the CCNP communicating with The Bryant Advantage!
