™
Cisco CCNA / CCNP Certification: OSPF E2 vs. E1 Routes
OSPF is a major matter on equally the CCNA and CCNP examinations, and it’s also The subject that requires probably the most awareness to depth. The place dynamic routing protocols like RIP and IGRP have just one router style, a examine a Cisco routing desk shows quite a https://socialhattori.com/ few different OSPF route types.
R1#demonstrate ip route
Codes: C – related, S – static, I – IGRP, R – RIP, M – mobile, B – BGP
D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter location
N1 – OSPF NSSA external kind one, N2 – OSPF NSSA external sort 2
E1 – OSPF external sort 1, E2 – OSPF external type two, E – EGP
With this tutorial, we’ll Have a look at the difference between two of these route varieties, E1 and E2.
Route redistribution is the entire process of getting routes uncovered by using 1 routing protocol and injecting People routes into An additional routing domain. (Static and related routes can be redistributed.) Any time a router functioning OSPF normally takes routes discovered by another routing protocol and tends to make them available to the other OSPF-enabled routers it’s speaking with, that router will become an Autonomous Method Border Router (ASBR).
Let’s perform with an case in point where by R1 is jogging each OSPF and RIP. R4 is in a similar OSPF domain as R1, and we would like R4 to learn the routes that R1 is learning via RIP. This implies we really need to conduct route redistribution within the ASBR. The routes that are being redistributed from RIP into OSPF will look as E2 routes on R4:
R4#present ip route ospf
O E2 5.one.one.1 [one hundred ten/20] by using 172.34.34.3, 00:33:21, Ethernet0
six.0.0.0/32 is subnetted, one subnets
O E2 6.1.1.1 [110/20] through 172.34.34.3, 00:33:21, Ethernet0
172.12.0.0/sixteen is variably subnetted, two subnets, 2 masks
O E2 172.12.21.0/30 [a hundred and ten/twenty] through 172.34.34.three, 00:33:32,
Ethernet0
O E2 seven.one.one.1 [110/20] by way of 172.34.34.3, 00:33:21, Ethernet0
fifteen.0.0.0/24 is subnetted, one subnets
O E2 15.one.one.0 [110/20] by means of 172.34.34.3, 00:33:32, Ethernet0
E2 would be the default route form for routes acquired via redistribution. The important thing with E2 routes is the fact that the price of these routes demonstrates only the price of the path within the ASBR to the final spot; the price of The trail from R4 to R1 is not really reflected In this particular Price. (Bear in mind OSPF’s metric to get a path is generally known as “cost”.)
In this instance, we wish the price of the routes to mirror all the path, not merely The trail amongst the ASBR and also the location network. To take action, the routes need to be redistributed into OSPF as E1 routes within the ASBR, as shown right here.
R1#conf t
Enter configuration commands, one particular per line. Finish with CNTL/Z.
R1(config)#router ospf 1
R1(config-router)#redistribute rip subnets metric-type 1
Now on R4, the routes show up as E1 routes and possess a bigger metric, considering that the entire route Charge is currently mirrored from the routing table.
O E1 5.one.one.1 [one hundred ten/ninety four] by using 172.34.34.three, 00:33:21, Ethernet0
O E1 6.1.one.1 [one hundred ten/100] by using 172.34.34.3, 00:33:21, Ethernet0
O E1 172.12.21.0/thirty [a hundred and ten/ninety four] by means of 172.34.34.three, 00:33:32, Ethernet0
O E1 7.one.1.1 [110/ninety four] by means of 172.34.34.3, 00:33:21, Ethernet0
O E1 fifteen.1.one.0 [one hundred ten/ninety four] through 172.34.34.three, 00:33:32, Ethernet0
Knowing the distinction between E1 and E2 routes is important for CCNP exam achievement, together with completely understanding a creation router’s routing table. Excellent luck in your scientific studies!