03-21-2012 08:30 AM - edited 03-07-2019 05:42 AM
Hi All,
I was working on home Lab redistributing EIGRP routes into OSPF.
R1 is router in OSPF domain.
R2 and R3 are redistributing routers running both OSPF and EIGRP.
R4 is router running EIGRP only.
R1 has fas thernet connection to R2 and serial connection to R3
When i do sh ip route on R1 it shows routes learned by fast ethernet only
R1#sh ip route
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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
10.0.0.0/24 is subnetted, 9 subnets
C 10.1.13.0 is directly connected, Serial0/0
C 10.1.12.0 is directly connected, FastEthernet0/0
C 10.1.0.0 is directly connected, Loopback0
O E2 10.4.2.0 [110/200] via 10.1.12.2, 00:13:36, FastEthernet0/0
O E2 10.4.3.0 [110/200] via 10.1.12.2, 00:13:36, FastEthernet0/0
O E2 10.4.0.0 [110/100] via 10.1.12.2, 00:13:36, FastEthernet0/0
O E2 10.4.1.0 [110/100] via 10.1.12.2, 00:13:36, FastEthernet0/0
O E2 10.1.24.0 [110/300] via 10.1.12.2, 00:13:36, FastEthernet0/0
O E2 10.1.23.0 [110/300] via 10.1.12.2, 00:13:36, FastEthernet0/0
Metric is same from R2 and R3 to R1.
So here is my thinking correct me if i am wrong --------------
If router learned routes having same Admin distance and metric from two routers.
it will choose the physical link which is faster as fast ethernet is more speed then serial T1 ??????
If it learn same routes via both serial links then it will load balance right??????????
Thanks
MAhesh
Solved! Go to Solution.
03-21-2012 08:48 AM
For sure,
OSPF uses cumulative metric which is calculated based on Bandwidth. The last hop on serial interface will add bigger value to total value than Fast Ethernet link.
You should be able to see both routes in OSPF topology as it should have Type 5 LSA from both neighbors.
Nik
03-21-2012 08:48 AM
For sure,
OSPF uses cumulative metric which is calculated based on Bandwidth. The last hop on serial interface will add bigger value to total value than Fast Ethernet link.
You should be able to see both routes in OSPF topology as it should have Type 5 LSA from both neighbors.
Nik
03-21-2012 09:20 AM
Hi Nik,
Thanks for reply.
i did this
R1#sh ip ospf database
OSPF Router with ID (10.1.0.1) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
10.1.0.1 10.1.0.1 1789 0x80000024 0x00E3D0 4
10.1.23.3 10.1.23.3 44 0x8000001F 0x000BED 2
10.1.24.2 10.1.24.2 1220 0x80000021 0x00F0A3 1
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
10.1.12.2 10.1.24.2 1723 0x8000001E 0x00EAC2
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
10.1.23.0 10.1.23.3 44 0x80000003 0x0059C6 30
10.1.23.0 10.1.24.2 1220 0x8000001D 0x0024E1 30
10.1.24.0 10.1.23.3 44 0x80000003 0x004ED0 30
10.1.24.0 10.1.24.2 1220 0x8000001D 0x0019EB 30
10.4.0.0 10.1.23.3 44 0x80000003 0x00F21E 10
10.4.0.0 10.1.24.2 1220 0x8000001D 0x00BD39 10
10.4.1.0 10.1.23.3 63 0x80000003 0x00E728 10
10.4.1.0 10.1.24.2 1239 0x8000001D 0x00B243 10
10.4.2.0 10.1.23.3 63 0x80000003 0x007D23 20
10.4.2.0 10.1.24.2 1239 0x8000001D 0x00483E 20
10.4.3.0 10.1.23.3 63 0x80000003 0x00722D 20
10.4.3.0 10.1.24.2 1239 0x8000001D 0x003D48 20
where 10.1.23.3 is R3 and we can see that it is learning EIGRP routes from R3 also but it did not put that in routing
table because of serial link speed right??
Mahesh
03-21-2012 05:37 PM
Correct
03-21-2012 09:17 PM
Hi Mahesh,
Your understanding is correct, The behaviour is because of the cost related to Serial interface,
Try to use the metric-type keyword during redistribution and you will see different result ( metric-type 1, Default is type 2 )
Regards
Sreenath
03-25-2012 06:29 AM
Hi Nik,
any thanks for correct explanation.
Thanks
MAhesh
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