OSPF routing issue
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10-01-2022 12:44 PM
Hello Guys,
I have this network where i need if x side is down then the traffic should go from y side. I am using OSPF and have check the routing table but I don't know where did i make a mistake. Can someone please correct me?
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10-01-2022 01:36 PM
default-information originate always
always cause issue here,
this make Edge router always advertise default route, remove it and check
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10-01-2022 10:30 PM
@MHM Cisco WorldI cannot remove the default route since I have to advertise the default route which is the routing protocol I have to use if i want to route with the isp.
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10-02-2022 05:28 AM
I dont want to remove information-origin
I want you to remove "always" keyword from information-origin
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10-02-2022 10:34 AM
@MHM Cisco World Still not working with only this command also
router ospf 1
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 1
default-information originate
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10-02-2022 10:55 AM
OSPF what the different between use always and not use always
*always meaning the router advertise the default route whatever if default route found or not in RIB
**no always meaning the router will advertise the default route IF default route found in RIB if not found then the router will not advertise the default route via OSPF
NOW the failure is two case
*failure of LINK connect Edge router to ISP
HERE USE ALWAYS IS make blackhole because it advertise default route even if it LINK to ISP is loss
**failure of Edge router (Edge router totally down)
HERE USE ALWAYS or NOT use ALWAYS will not effect because the Edge router that advertise the default route via OSPF is totally down...
so you face failure of LINK and you use ALWAYS you make BLACKHOLE.
so I recommend not use ALWAYS keyword
and if you dont have default route add default route.
MHM
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10-02-2022 01:33 PM - edited 10-02-2022 01:42 PM
Hello
both rtrs
router ospf 1
no default-information originate always
no default-information originate
router 1
router ospf 1
default-information originate metric-type1
router 2
router ospf 1
default-information originate
Lastly even though it now shown in the rtr configs, I do see a default static in the route rable readouts, probably suggest also to make that default condictinal with some ipsla tracking
Example
ip sla 1
icmp-echo x.x.x.x source-ip x.x.x.x
timeout 1000
threshold 2000
frequency 15
ip sla schedule 1 start now life forever
track 10 rtr1 reachabilty
ip route 0.0.0.0 0.0.0.0 192.168.182.2 track10 name default-route
Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.
Kind Regards
Paul
