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Learning new ip route and adding to Routing Table

IP Routing question. New host route 192.168.20.181 is learned by my router. The network 192.168.20.0/24 is new and does not exist on the network. OSPF is the routing protocol on the router and the router tries to add this to the routing table - see debug output below. I have 2 questions:-

1. Can someone confirm that the router sees that this is a /32 host route and tries to add this to the RT but why does it also delete 192.168.20.0 - is it because this is a Class C address?

May 14 11:00:40 UTC: RT: add 192.168.20.181/32 via 19.50.100.1, ospf metric [110/20]

.May 14 11:00:40 UTC: RT: add 192.168.20.181/32 via 19.50.100.2, ospf metric [110/20]

.May 14 11:00:50 UTC: RT: del 192.168.20.181/32 via 19.50.100.1, ospf metric [110/20]

.May 14 11:00:50 UTC: RT: del 192.168.20.181/32 via 19.50.100.2, ospf metric [110/20]

.May 14 11:00:50 UTC: RT: delete subnet route to 192.168.20.181/32

.May 14 11:00:50 UTC: RT: delete network route to 192.168.20.0

Question 2.

Also, the route apparently is originating from a next-hop 3rd party router. This company have a static route for 192.168.20.0/24 configured on this box. OSPF is configured on this router and they do have a redistribute static route-map Test but the route-map Test does not include this network. Is there any chance that the OSPF process is redistributing all statics into OSPF rather than the specific Test Route map?

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: Learning new ip route and adding to Routing Table

Mary,

1) As we remove the subnet (192.168.20.181/32)from the routing table we also remove the majornet (192.168.20.0/24) used in the IOS internal data structures.

2) Not if the route-map is configured properly.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
1 REPLY
Cisco Employee

Re: Learning new ip route and adding to Routing Table

Mary,

1) As we remove the subnet (192.168.20.181/32)from the routing table we also remove the majornet (192.168.20.0/24) used in the IOS internal data structures.

2) Not if the route-map is configured properly.

Hope this helps,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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