What is the difference between OSPF Exteral Type 1 (O E1) & External Type 2

What is the difference between OSPF Exteral Type 1 (O E1) &
External Type 2 (O E2) routes????

Question Posted / shahin

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What is the difference between OSPF Exteral Type 1 (O E1) & External Type 2 (O E2) routes????..

Answer / kamalpreet singh

when we redistribute a protocol in ospf, by default it
accept those route as E2 in ospf domain. E1 & E2 is external
type 1 and rxternal type 2. in Cisco external route are E2
by nature.

Basically difference between E1 and E2 is : E1 includes
internal cost to ASBR added to external cost, E2 does not
include internal cost. it is same as external cost.

E1 is prefered if route is equal cost path exist.

Example: R1-R2-R3 is connected and R3 is a ASBR. and suppose
a cost of between R1 to R2 is 10 and R2 to R3 is 10. Cost
of external router on R3(asbr) is 1800. now if you thik
about E1 cost to external route from R1 is (10+10+1800) 1820
but in case of E2 it is 1800..

E1 is usefull when there are multiple ASBR to same
destination and E2 is usefull when there is only one ASBR in
to reach destinaltion.

for any query, intv.que@gmail.com

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What is the difference between OSPF Exteral Type 1 (O E1) & External Type 2 (O E2) routes????..

Answer / jitendera kuamr sin ha

let see the comand

router A
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface Serial0/1
ip address 10.1.1.1 255.255.255.252
clockrate 64000
!
router ospf 1
network 10.1.1.0 0.0.0.3 area 0

outer B
interface Loopback0
ip address 2.2.2.2 255.255.255.255
!
interface Serial0
ip address 10.1.1.2 255.255.255.252
!
interface Serial 1
ip address 10.1.1.5 255.255.255.252
!
router eigrp 1
network 10.0.0.0
!
router ospf 1
network 10.1.1.0 0.0.0.3 area 0

outer C
interface Loopback0
ip address 3.3.3.3 255.255.255.255
!
interface Loopback1
ip address 5.5.5.5 255.0.0.0
!
interface Loopback2
ip address 6.6.6.6 255.240.0.0
!
interface Loopback3
ip address 145.5.5.5 255.255.0.0
!
interface Loopback4
ip address 146.6.6.6 255.255.240.0
!
interface Loopback5
ip address 205.5.5.5 255.255.255.0
!
interface Loopback6
ip address 206.6.6.6 255.255.255.240
!
interface Serial0
ip address 10.1.1.6 255.255.255.252
!
router eigrp 1
network 5.0.0.0
network 6.0.0.0
network 10.0.0.0
network 145.5.0.0
network 146.6.0.0
network 205.5.5.0
network 206.6.6.0
no auto-summary

Verify that Routers A and B have established an OSPF
neighbor relationship.

rtrA#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/ - 00:00:36 10.1.1.2 Serial0/1

verify that Routers B and C have formed an EIGRP neighbor
relationship.
trB#show ip eigrp neighbors
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 10.1.1.6 Se1 11 00:25:42 308 2280 0 4

Verify that Router B is receiving the six EIGRP routes from
Router C

rtrB#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M -
mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF
inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external
type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E
- EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * -
candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
D 205.5.5.0/24 [90/40640000] via 10.1.1.6, 00:26:25, Serial1
206.6.6.0/28 is subnetted, 1 subnets
D 206.6.6.0 [90/40640000] via 10.1.1.6, 00:26:25, Serial1
D 5.0.0.0/8 [90/40640000] via 10.1.1.6, 00:26:25, Serial1
6.0.0.0/12 is subnetted, 1 subnets
D 6.0.0.0 [90/40640000] via 10.1.1.6, 00:26:25, Serial1
D 145.5.0.0/16 [90/40640000] via 10.1.1.6, 00:26:25, Serial1
10.0.0.0/30 is subnetted, 2 subnets
C 10.1.1.0 is directly connected, Serial0
C 10.1.1.4 is directly connected, Serial1
146.6.0.0/20 is subnetted, 1 subnets
D 146.6.0.0 [90/40640000] via 10.1.1.6, 00:26:27, Serial1

Modify the configuration on Router B to redistribute the
classful EIGRP routes into OSPF.

router ospf 1
redistribute eigrp 1

When the command redistribute eigrp 1 is entered, the router
will give you the following friendly reminder:

rtrB(config-router)#redistribute eigrp 1
% Only classful networks will be redistributed

Determine the routes that have been redistributed by
examining the IP routing table on Router A.

rtrA#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M -
mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF
inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external
type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E
- EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia -
IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
O E2 205.5.5.0/24 [110/20] via 10.1.1.2, 00:33:23, Serial0/1
O E2 5.0.0.0/8 [110/20] via 10.1.1.2, 00:33:23, Serial0/1
O E2 145.5.0.0/16 [110/20] via 10.1.1.2, 00:33:23, Serial0/1
10.0.0.0/30 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0/1

nly the EIGRP classful routes were redistributed into OSPF.
As you can see in the routing table on Router A, EIGRP
routes were redistributed as external type 2 with a cost or
metric of 20. This information can also be found by
inspecting the OSPF database on Router B.

rtrB#show ip ospf database external
OSPF Router with ID (2.2.2.2) (Process ID 1)
Type-5 AS External Link States
LS age: 410
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 5.0.0.0 (External Network Number )
Advertising Router: 2.2.2.2
LS Seq Number: 80000004
Checksum: 0x642C
Length: 36
Network Mask: /8
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
LS age: 419
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 145.5.0.0 (External Network Number )
Advertising Router: 2.2.2.2
LS Seq Number: 80000004
Checksum: 0x5F9
Length: 36
Network Mask: /16
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
LS age: 435
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 205.5.5.0 (External Network Number )
Advertising Router: 2.2.2.2
LS Seq Number: 80000004
Checksum: 0xBEFE
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 0.0.0.0
External Route Tag: 0
this is mine confregation so some data like ip address mi
modified nad some data is omoted

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What is the difference between OSPF Exteral Type 1 (O E1) & External Type 2 (O E2) routes????..

Answer / jitendera kumar sinha

a very good question-
here is specification between two

i am going to explain brefly

please read it carefully.

Route redistribution is the process of taking routes
learned via one routing protocol and injecting those routes
into another routing domain. (Static and connected routes
can also be redistributed.) When a router running OSPF takes
routes learned by another routing protocol and makes them
available to the other OSPF-enabled routers it's
communicating with, that router becomes an Autonomous System
Border Router (ASBR).

Let's work with an example where R1 is running both OSPF and
RIP. R4 is in the same OSPF domain as R1, and we want R4 to
learn the routes that R1 is learning via RIP. This means we
have to perform route redistribution on the ASBR. The routes
that are being redistributed from RIP into OSPF will appear
as E2 routes on R4:

what is asbr-Autonomous System Border Router
(ASBR).Autonomous System Boundary Router (ASBR) is a router
located between an OSPF autonomous system and a non-OSPF
network (such as RIP). ASBRs run both OSPF and another
routing protocol, such as RIP. ASBRs must reside on a
non-stub OSPF area.

and this type of route is called ospf e2 route

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What is the difference between OSPF Exteral Type 1 (O E1) & External Type 2 (O E2) routes????..

Answer / jitu

answer 1 continue

let there are three router

r1---------r2------r3

r1------area 0 protocol ospf
r2------area1 protocol ospf9this is abr router)
r3---------area2 protocol rip(this is asbr router)

now we have to make redisrtubution on asbr router.

so this is called e type

now

e1 is so simlple you make a digram with therer router and
run each by single ospf enabled protocol that is called e1

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