Re: OSPF Metric of > 65535??? WTF!

Maximum interface cost is 65535. The maximum OSPF metric is 2^32.

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Marko Milivojevic - CCIE #18427
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On Tue, Oct 19, 2010 at 17:47, Mike Kiefer <mkiefer74_at_hotmail.com> wrote:
> I was always under the impression the maximum metric of OSPF is 65535.
> Anything beyond that wouldn't make it into the routing table. The behavior
> would be similar to a RIP route with a hop count of 16 that's considered
> unreachable.
>
> I noticed a few routes on our production network that exceeded 65535 mainly
> because of network engineer stupidity.
>
> So I made a real simple lab in GNS3. R1 connects to R2 connects to R3. R1, R2,
> and R3 have 1.1.1.1, 2.2.2.2, and B 3.3.3.3 as loopbacks and all of the links
> are maxed out with ip ospf cost 65535.
>
>
> R1(config-if)#do sh ip route
> Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
> B  B  B  D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> B  B  B  N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> B  B  B  E1 - OSPF external type 1, E2 - OSPF external type 2
> B  B  B  i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
> B  B  B  ia - IS-IS inter area, * - candidate default, U - per-user static
> route
> B  B  B  o - ODR, P - periodic downloaded static route
>
> Gateway of last resort is not set
>
> B  B  1.0.0.0/32 is subnetted, 1 subnets
> C B  B  B  1.1.1.1 is directly connected, Loopback0
> B  B  2.0.0.0/32 is subnetted, 1 subnets
> O IA B  B 2.2.2.2 [110/131070] via 12.1.1.2, 00:07:10, FastEthernet0/0
> B  B  3.0.0.0/32 is subnetted, 1 subnets
> O IA B  B 3.3.3.3 [110/196605] via 12.1.1.2, 00:02:11, FastEthernet0/0
> B  B  12.0.0.0/24 is subnetted, 1 subnets
> C B  B  B  12.1.1.0 is directly connected, FastEthernet0/0
> B  B  13.0.0.0/24 is subnetted, 1 subnets
> O B  B  B  13.1.1.0 [110/131070] via 12.1.1.2, 00:02:21, FastEthernet0/0
>
>
> R1(config-if)#do sh ip ospf data summ
>
> B  B  B  B  B  B OSPF Router with ID (1.1.1.1) (Process ID 1)
>
> B  B  B  B  B  B  B  B Summary Net Link States (Area 0)
>
> B Routing Bit Set on this LSA
> B LS age: 654
> B Options: (No TOS-capability, DC, Upward)
> B LS Type: Summary Links(Network)
> B Link State ID: 2.2.2.2 (summary Network Number)
> B Advertising Router: 2.2.2.2
> B LS Seq Number: 80000002
> B Checksum: 0xEE3D
> B Length: 28
> B Network Mask: /32
> B  B  B  B TOS: 0 B Metric: 65535
>
> B Routing Bit Set on this LSA
> B LS age: 471
> B Options: (No TOS-capability, DC, Upward)
> B LS Type: Summary Links(Network)
> B Link State ID: 3.3.3.3 (summary Network Number)
> B Advertising Router: 3.3.3.3
> B LS Seq Number: 80000001
> B Checksum: 0xA480
> B Length: 28
> B Network Mask: /32
> B  B  B  B TOS: 0 B Metric: 65535
>
> How do I get a routing metric > 65535? Why are both 2.2.2.2 and 3.3.3.3 only
> showing 65535 in the DB and higher metrics in the routing table? Isn't the
> 65535 based on the fact that there are only 16 bits for metric?
>
> What gives???
>
>
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