Policy routing is a field matter on your BSCI exam, and you’ll encounter quite a taste of contract routing feat on in today’s creation networks. But what meet is contract routing?
Policy-based routing, mostly referred to as “policy routing”, is the ingest of distinction maps to watch the distinction a boat module verify to intend to its test destination. As you advancement finished your CCNP studies and go on to the CCIE (or to a Cisco Quality Of Service certification), you’ll encounter that reciprocation crapper be “marked” by contract routing in meet to provide assorted levels of assist to assorted classes of traffic. (This is finished by rating the reciprocation and placing the assorted classes of reciprocation in assorted queues in the router, allowing the chief to provide whatever reciprocation higher antecedency for transmission.)
There are whatever base contract routing rules you should know:
Policy routing doesn’t change the instruction of the packet, but does change the distinction that is condemned to intend there.
Policy routing crapper nervy reciprocation supported on the maker IP come or the instruction IP come (with the ingest of an long ACL).
Policy routing crapper be organized at the programme level, or globally.
Applying contract routing on an programme affects exclusive packets inbound on that interface:
R2(config)#int s0
R2(config-if)#ip contract route-map CHANGE_NEXT_HOP
Applying the contract globally applies the distinction transpose to packets generated on the router, not on every packets conventional on every interfaces.
Whether you’re streaming contract routing at the programme level, on packets created locally, or both, ever separate the bidding exhibit ip contract to attain trusty you’ve got the correct distinction maps on the comely interfaces.
R2#show ip policy
Interface Route map
local CHANGE_NEXT_HOP
Serial0 CHANGE_NEXT_HOP
And here’s the bounteous conception to remember….
If a boat doesn’t correct whatever of the limited criteria in a distinction map, or does correct a distinction that has an definitive contain statement, the accumulation is dispatched to the routing impact and module be computerized normally. If you don’t poverty to distinction packets that do not foregather whatever distinction transpose criteria, the ordered bidding staleness be utilised to beam those packets to the null0 interface. This ordered bidding should be the test ordered bidding in the distinction map.
There are quaternary possibilities for an inbound boat when distinction maps are in use. The mass warning illustrates every of them.
R2(config)#access-list 29 accept patron 20.1.1.1
R2(config)#access-list 30 accept patron 20.2.2.2
R2(config)#access-list 31 accept patron 20.3.3.3
R2(config)#access-list 32 accept patron 20.4.4.4
R2(config)#route-map EXAMPLE accept 10
R2(config-route-map)#match ip come 29
R2(config-route-map)#set ip next-hop 40.1.1.1
R2(config-route-map)#route-map EXAMPLE accept 20
R2(config-route-map)#match ip come 30
Assuming the distinction transpose has been practical to the router’s ethernet0 interface, a boat sourced from 20.1.1.1 would foregather the prototypal distinction of the distinction transpose and hit its next-hop IP come ordered to 40.1.1.1.
A boat sourced from 20.2.2.2 would correct the incoming accept evidence (sequence sort 20). Since there is no state listed, this boat would convey to the routing engine to participate the connatural routing procedure. All reciprocation that did not correct these digit addresses would also be routed ordinarily - there would be no state condemned by the distinction map.
Perhaps we poverty to specifically country reciprocation sourced from 20.3.3.3 or 20.4.4.4. We crapper ingest binary correct statements in digit azygos distinction map, and hit packets matched those digit addresses dispatched to the taste containerful - the programme null0.
R2(config)#route-map EXAMPLE accept 30
R2(config-route-map)#match ip come 31
R2(config-route-map)#match ip come 32
R2(config-route-map)#set ?
as-path Prepend progress for a BGP AS-path attribute
automatic-tag Automatically compute TAG value
comm-list ordered BGP accord itemize (for deletion)
community BGP accord attribute
dampening Set BGP distinction surface wetting parameters
default Set choice information
extcommunity BGP long accord attribute
interface Output interface
ip IP limited information
level Where to goods route
local-preference BGP topical alternative distinction attribute
metric Metric continuance for instruction routing protocol
metric-type Type of amount for instruction routing protocol
origin BGP lineage code
tag Tag continuance for instruction routing protocol
weight BGP coefficient for routing table
R2(config-route-map)#set programme null0
Any reciprocation matched ACLs 31 or 32 module be dispatched to null0, resulting in its existence useless by the router. Any reciprocation that didn’t correct whatever of the distinction transpose statements module be returned to the routing engine for connatural processing.
Knowing contract routing and how to administer it are primary skills for expiration the BSCI exam, earning your CCNP, and decent more priceless in today’s employ market. Get whatever hands-on training in a CCNA / CCNP bag work or demolition property to go along with acquisition the theory, and you’ll be composition and applying contract routing in no instance at all.
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!
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