cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
822
Views
10
Helpful
9
Replies

OSPF E2 Over Static

muhammad-furqan
Level 1
Level 1

My perimeter router is connected with my branch over a leased circuit and remote branch network appears in routing table as OE2, my floating static route on perimeter is installed and pointing towards ISDN interface with the AD of 200 and redistributed into OSPF, whenever leased circuit goes down this static route will install in routing table and redistributed into ospf, but if leased circuit comes up the the remote branch subnet will not appear in routing table through OSPF, coz the perimiter router dont trust that E2 route coz it have the static route to same destination which its redistributing into ospf, so it dont install that already redistributed route which it received from another ASBR, if i stop redistributing the static on perimeter then it will install that E2 route received by other ASBR.

How can i prevent this perimeter to keep install that static route over O E2 even primary circuit restores

9 Replies 9

Edison Ortiz
Hall of Fame
Hall of Fame

Increase the metric on the redistribute command for the static.

For instance,

router ospf 1

redistribute static metric 50 subnets

The router coming from your neighbor router would have a metric of 20 (default metric on E2). Metric of 20 will be preferred over metric of 50 when comparing both routers in the RIB.

HTH,

__

Edison.

I already try this but no success, metric is not the cause of problem, router recieved network from another ASBR with type E2 but also have static route for same subnet and feel better to redistribute its own static route into ospf rather then other learned ASBR route

Please post the show ip os data from your router and tell us which route is the one in question.

__

Edison.

R2#sh ip ospf database

OSPF Router with ID (192.168.5.2) (Process ID 1293)

Router Link States (Area 971)

Link ID ADV Router Age Seq# Checksum Link count

192.168.1.1 192.168.1.1 303 0x80000004 0x007591 3

192.168.4.3 192.168.4.3 177 0x80000002 0x001C58 2

192.168.5.2 192.168.5.2 75 0x80000007 0x002865 4

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

192.168.4.0 192.168.4.3 50 0x80000001 0x00CFF2 0

192.168.6.0 192.168.5.2 46 0x80000001 0x00C744 0

Subnet is 192.168.6.0 above output is taken when leased circuit is down and ISDN is up

Below output is taken when leased circuit is up

R2#sh ip ospf database

OSPF Router with ID (192.168.5.2) (Process ID 1293)

Router Link States (Area 971)

Link ID ADV Router Age Seq# Checksum Link count

192.168.1.1 192.168.1.1 525 0x80000004 0x007591 3

192.168.4.3 192.168.4.3 400 0x80000002 0x001C58 2

192.168.5.2 192.168.5.2 297 0x80000007 0x002865 4

Type-5 AS External Link States

Link ID ADV Router Age Seq# Checksum Tag

192.168.4.0 192.168.4.3 272 0x80000001 0x00CFF2 0

192.168.6.0 192.168.4.3 17 0x80000001 0x00B907 0

4.3 is neighbour ASBR which is injecting route as E2, 5.2 is R2 itself

R2 will not switch back to E2 route even it come back again the only way to do so is to convert that E2 into type 2 or 3 but how?

I did an exercise in lab in which i remove the command redistribute static in R2 and problem is resolved and R2 will switch back to E2 when link is up coz after removing this command R2 will no longer ASBR and then it trust same routes of another ASBR.

I also removed the redistribution from R3 (4.3) this will resolve the issue coz then it forward the route as type2 and R2 will trust on that route rather then its own redistributed, but in live network both solutions are not aplicable

I'm unable to duplicate your problem. Again, I'm altering the metric on the redistribute static on the router connected to the ISDN.

I'm tagging the route from both routers, the one doing the original redistribution and the one doing the redistribution with static.

I have the following setup

R1 <----> R2 <---> R3

R3 is doing the original redistribution, on this example, I'm redistributing connected (just loopback0)

Rack1R3#sh run | sec router os

router ospf 1

log-adjacency-changes

redistribute connected subnets tag 3

network 192.168.23.3 0.0.0.0 area 0

!

!

Rack1R3#sh ip route connected

C 192.168.23.0/24 is directly connected, Serial1/1

150.1.0.0/32 is subnetted, 1 subnets

C 150.1.3.3 is directly connected, Loopback0

___

R2 is receiving the route as E2 with metric of 20. It also has a redistribute static with metric of 50.

Rack1R2#sh run | sec router os

router ospf 1

log-adjacency-changes

redistribute static metric 50 subnets tag 2

network 192.168.12.2 0.0.0.0 area 0

network 192.168.23.2 0.0.0.0 area 0

!

!

Rack1R2#sh ip route

C 192.168.12.0/24 is directly connected, Serial1/0

C 192.168.23.0/24 is directly connected, Serial1/1

150.1.0.0/32 is subnetted, 1 subnets

O E2 150.1.3.3 [110/20] via 192.168.23.3, 00:04:05, Serial1/1

Rack1R2(config-if)#do show run | i ip route

ip route 150.1.3.3 255.255.255.255 192.168.12.1 200

Rack1R2(config-if)#

___

R1 is the router where the changes are observed when the link goes down. Currently, it's getting its E2 from R3 (tagged as 3) and metric is 20.

Rack1R1#sh ip route 150.1.3.3

Routing entry for 150.1.3.3/32

Known via "ospf 1", distance 110, metric 20

Tag 3, type extern 2, forward metric 128

Last update from 192.168.12.2 on Serial1/0, 00:05:29 ago

Routing Descriptor Blocks:

* 192.168.12.2, from 150.1.3.3, 00:05:29 ago, via Serial1/0

Route metric is 20, traffic share count is 1

Route tag 3

____

If I bring the link down between R2 and R3, the redistribute static on R2 will kick in with metric of 50 and tag of 2.

___

Rack1R1#sh ip route 150.1.3.3

Routing entry for 150.1.3.3/32

Known via "ospf 1", distance 110, metric 50

Tag 2, type extern 2, forward metric 64

Last update from 192.168.12.2 on Serial1/0, 00:00:31 ago

Routing Descriptor Blocks:

* 192.168.12.2, from 192.168.23.2, 00:00:31 ago, via Serial1/0

Route metric is 50, traffic share count is 1

Route tag 2

____

If I bring the link up, it returns to R3's route as expected.

Rack1R1#sh ip route 150.1.3.3

Routing entry for 150.1.3.3/32

Known via "ospf 1", distance 110, metric 20

Tag 3, type extern 2, forward metric 128

Last update from 192.168.12.2 on Serial1/0, 00:00:00 ago

Routing Descriptor Blocks:

* 192.168.12.2, from 150.1.3.3, 00:00:00 ago, via Serial1/0

Route metric is 20, traffic share count is 1

Route tag 3

____

In order to help you further, we are going to need to see some configs from your routers.

HTH,

__

Edison.

Please rate helpful posts

My network diagram is as following

R1------R2-----R3-------R4

|_______________|

R2 and R4 have direct serial link, a static route for R4 lan is pointing towards this link and R3 is doing actual redistribution, here i attach sh run of all routers

You forgot to mention the route is being brought from RIP on R3.

When the link is brought back up, R3 will prefer the route from R2 since it has an administrative distance of 110 over the RIP administrative distance of 120.

In order to correct the problem, you need to change the administrative distance in RIP between R3 and R4 so RIPs routes are preferred over OSPF.

Example,

router rip

distance 109

HTH,

__

Edison.

Please rate helpful posts

In actual scenario R3 is PE and redistributing another OSPF process in our OSPF process, the distance command will help to resolve the issue but PE is under control of SP and we will request to change the Distance but not sure they will accept or not, i think distance is locally significant and we can't do any thing related to this am i correct?

i think distance is locally significant and we can't do any thing related to this am i correct?

Correct. The PE Router (R3) must have the RIP route on its routing table. When R3 converges with R2 after a service restoration, R2 has a better route for that network with OSPF and R3 will never return to the original RIP route coming from R4.

__

Edison.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: