[c-nsp] OSPF routing question

[Lee Starnes]

Thank you all for the distance change to 254. That resolved the issue.

On Tue, Jul 17, 2018 at 7:57 PM, Erik Sundberg <ESundberg at nitelusa.com>
wrote:

> Lee,
>
>
> Change the Floating static route to an administrative distance of 254, so
> it is higher than OSPF.
>
>
> router static
>  address-family ipv4 unicast
>  45.x.x.0/22 Null0 *254*
>
>
> When the route is learned via OSPF it will have a metric of 110 and the
> ospf route will be installed into the routing table.
>
> When the route is not learned via OSPF the floating static router on your
> Edge router will be active. This will still allow BGP to advertise the
> route.
>
>
>
> Also, if you don't want to advertise the floating static route to other
> devices in your network you can do the following.
>
> Add the tag 1 on the static route will stop it from being redistributed in
> your network.
>
>
> router static
>  address-family ipv4 unicast
>  45.x.x.0/22 Null0 254 *tag 1*
>
>
> router ospf 1
>  log adjacency changes
>  redistribute static* route-policy **IPV4-OSPF-REDIST-STATIC*
>
> *route-policy IPV4-OSPF-REDIST-STATIC*
>
> *  if tag eq 1 then *
> *    drop*
> *  endif*
> *  done*
>
> If a static route has the tag of 1 it will not be redistributed into OSPF,
> so the rest of the network will not learn about the route.
>
>
> ---------------------
>
> Side note, most ISP's will only advertise there Loopback and Core
> "Circuits" IPs in there IGP.  They will run iBGP between all of the there
> devices and allow BGP to redistribute the static and connected interfaces.
> BGP is also easier to manipulate routes on your network. Send me an email
> if you would like to know more.
>
> Here is an old but still very relevant power point on this.
>
> https://www.pacnog.org/pacnog2/track2/routing/a3-1up.pdf
> 3 - OSPF for ISPs - PacNOG
> <https://www.pacnog.org/pacnog2/track2/routing/a3-1up.pdf>
> www.pacnog.org
> © 2005 Cisco Systems, Inc. All rights reserved. 1 Session Number
> Presentation_ID Cisco Confidential Deploying OSPF for ISPs ISP/IXP Workshops
>
>
>
>
>
>
>
>
>
>
>
> ------------------------------
> *From:* cisco-nsp <cisco-nsp-bounces at puck.nether.net> on behalf of Lee
> Starnes <lee.t.starnes at gmail.com>
> *Sent:* Tuesday, July 17, 2018 4:17:25 PM
> *To:* cisco-nsp at puck.nether.net
> *Subject:* [c-nsp] OSPF routing question
>
> Hello everyone,
>
> I have a question about OSPF route redistribution. We have no issues
> redistributing subnets in the network out of our /19 blocks. But we have a
> /22 block that the entire /22 is allocated to a single client. The routes
> redistribute across all the all switches except back to the edge routers
> that announce them via BGP to our upstream carriers. This being because
> there are holdown routes for the BGP on this of the same size IP block. Is
> there a way to allow the /22 block to propagate to the edge routers and
> still maintain the hold down routes we need to announce that /22 via BGP to
> our various upstream carriers?
>
> Edge routers are configured as such:
>
> router static
>  address-family ipv4 unicast
>  45.x.x.0/22 Null0 19
>
> router bgp ASNUMBER
> address-family ipv4 unicast
> network 45.x.x.0/22
>
>
> router ospf NUMBER
>  log adjacency changes
>  redistribute connected
>  redistribute static
>  area W.X.Y.Z
>   !
>   interface TenGigE0/3/0/0
>    passive disable
>   !
>   interface TenGigE0/3/3/0
>    passive disable
>   !
>
>
> Any ideas are greatly appreciated.
>
> -Lee
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