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Cisco CCNA / CCNP Certification: OSPF E2 vs. E1 Routes
OSPF is A serious matter on the two the CCNA and CCNP exams, and it’s also the topic that requires essentially the most interest to element. Where by dynamic routing protocols for instance RIP and IGRP have only one router variety, a take a look at a Cisco routing table shows several diverse OSPF route types.
R1#display ip route
Codes: C – connected, S – static, I – IGRP, R – RIP, M – cell, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter place
N1 – OSPF NSSA exterior kind https://socialhattori.com/ 1, N2 – OSPF NSSA external type two
E1 – OSPF external sort one, E2 – OSPF external variety 2, E – EGP
With this tutorial, we’ll Look into the difference between two of those route varieties, E1 and E2.
Route redistribution is the whole process of getting routes discovered by way of just one routing protocol and injecting those routes into One more routing domain. (Static and linked routes can be redistributed.) Every time a router running OSPF normally takes routes discovered by A different routing protocol and helps make them accessible to the opposite OSPF-enabled routers it’s communicating with, that router results in being an Autonomous Procedure Border Router (ASBR).
Let’s work by having an example in which R1 is working equally OSPF and RIP. R4 is in the exact same OSPF domain as R1, and we would like R4 to find out the routes that R1 is Finding out by using RIP. This implies we need to perform route redistribution within the ASBR. The routes that are being redistributed from RIP into OSPF will appear as E2 routes on R4:
R4#exhibit ip route ospf
O E2 5.one.1.one [one hundred ten/20] by using 172.34.34.three, 00:33:21, Ethernet0
six.0.0.0/32 is subnetted, 1 subnets
O E2 6.1.1.1 [one hundred ten/twenty] by means of 172.34.34.3, 00:33:21, Ethernet0
172.12.0.0/sixteen is variably subnetted, 2 subnets, two masks
O E2 172.12.21.0/thirty [one hundred ten/20] by means of 172.34.34.three, 00:33:32,
Ethernet0
O E2 seven.1.1.1 [110/20] by means of 172.34.34.three, 00:33:21, Ethernet0
fifteen.0.0.0/24 is subnetted, 1 subnets
O E2 fifteen.1.1.0 [a hundred and ten/twenty] by way of 172.34.34.three, 00:33:32, Ethernet0
E2 is the default route kind for routes realized by means of redistribution. The main element with E2 routes is always that the cost of these routes demonstrates only the price of The trail with the ASBR to the ultimate location; the expense of the path from R4 to R1 isn't reflected On this Charge. (Bear in mind OSPF’s metric for the path is known as “Price tag”.)
In this example, we wish the price of the routes to mirror the entire path, not only The trail concerning the ASBR as well as the spot network. To do so, the routes must be redistributed into OSPF as E1 routes over the ASBR, as demonstrated here.
R1#conf t
Enter configuration instructions, just one for each line. Close with CNTL/Z.
R1(config)#router ospf one
R1(config-router)#redistribute rip subnets metric-form 1
Now on R4, the routes show up as E1 routes and have a larger metric, because the entire path Price tag has become mirrored while in the routing desk.
O E1 five.1.one.one [110/94] by using 172.34.34.three, 00:33:21, Ethernet0
O E1 six.1.one.one [110/one hundred] by using 172.34.34.three, 00:33:21, Ethernet0
O E1 172.twelve.21.0/30 [110/ninety four] via 172.34.34.3, 00:33:32, Ethernet0
O E1 7.one.one.one [110/ninety four] through 172.34.34.3, 00:33:21, Ethernet0
O E1 fifteen.1.one.0 [one hundred ten/94] by means of 172.34.34.3, 00:33:32, Ethernet0
Knowing the distinction between E1 and E2 routes is vital for CCNP Test achievement, together with thoroughly being familiar with a manufacturing router’s routing table. Superior luck in your scientific tests!