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

Interesting. I guess it's almost impossible to snuff out a route with cost
alone. This would make one hell of a good OEQ, if the R&S still had them.

I did manage to find this with the help of Google.

http://puck.nether.net/pipermail/cisco-nsp/2003-January/001986.html

> From: markom_at_ipexpert.com
> Date: Tue, 19 Oct 2010 17:50:00 +0000
> Subject: Re: OSPF Metric of > 65535??? WTF!
> To: mkiefer74_at_hotmail.com
> CC: ccielab_at_groupstudy.com
>
> Maximum interface cost is 65535. The maximum OSPF metric is 2^32.
>
> --
> Marko Milivojevic - CCIE #18427
> Senior Technical Instructor - IPexpert
>
> FREE CCIE training: http://bit.ly/vLecture
>
> Mailto: markom_at_ipexpert.com
> Telephone: +1.810.326.1444
> Web: http://www.ipexpert.com/
>
> 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 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
> > 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
> >
> > 1.0.0.0/32 is subnetted, 1 subnets
> > C 1.1.1.1 is directly connected, Loopback0
> > 2.0.0.0/32 is subnetted, 1 subnets
> > O IA 2.2.2.2 [110/131070] via 12.1.1.2, 00:07:10, FastEthernet0/0
> > 3.0.0.0/32 is subnetted, 1 subnets
> > O IA 3.3.3.3 [110/196605] via 12.1.1.2, 00:02:11, FastEthernet0/0
> > 12.0.0.0/24 is subnetted, 1 subnets
> > C 12.1.1.0 is directly connected, FastEthernet0/0
> > 13.0.0.0/24 is subnetted, 1 subnets
> > O 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
> >
> > OSPF Router with ID (1.1.1.1) (Process ID 1)
> >
> > Summary Net Link States (Area 0)
> >
> > Routing Bit Set on this LSA
> > LS age: 654
> > Options: (No TOS-capability, DC, Upward)
> > LS Type: Summary Links(Network)
> > Link State ID: 2.2.2.2 (summary Network Number)
> > Advertising Router: 2.2.2.2
> > LS Seq Number: 80000002
> > Checksum: 0xEE3D
> > Length: 28
> > Network Mask: /32
> > TOS: 0 Metric: 65535
> >
> > Routing Bit Set on this LSA
> > LS age: 471
> > Options: (No TOS-capability, DC, Upward)
> > LS Type: Summary Links(Network)
> > Link State ID: 3.3.3.3 (summary Network Number)
> > Advertising Router: 3.3.3.3
> > LS Seq Number: 80000001
> > Checksum: 0xA480
> > Length: 28
> > Network Mask: /32
> > TOS: 0 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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> >
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Received on Tue Oct 19 2010 - 13:00:28 ART