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 <[email protected]> on behalf of Lee Starnes
<[email protected]>
Sent: Tuesday, July 17, 2018 4:17:25 PM
To: [email protected]
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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