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I am redistributing an eBGP route into OSPF, I see the route flooded in the database, but it is not installed in the routing table on the other routers.

What would cause this route not to install in the routing table?

Below is the some troubleshooting output from dallas and atlanta. I'm expecting the route 172.16.192.0/19 to be available on atlanta.

asr1k/dallas#show run | sec router ospf 1

router ospf 1 vrf blue
 router-id 172.18.255.1
 ispf
 prefix-suppression
 timers throttle spf 10 100 1000
 timers throttle lsa 10 100 1000
 timers lsa arrival 50
 timers pacing flood 5
 timers pacing retransmission 60
 redistribute static subnets
 redistribute bgp 65001 subnets tag 0
 passive-interface default
 no passive-interface GigabitEthernet0/0/2.100
 no passive-interface Tunnel1000
 network 172.16.0.0 0.15.255.255 area 0
 neighbor 172.16.254.25
 neighbor 172.16.254.19
 neighbor 172.16.254.22
 neighbor 172.16.254.20
 neighbor 172.16.255.27 cost 5000
 maximum-paths 1

asr1k/dallas#show ip route vrf blue 172.16.192.0

Routing Table: blue
Routing entry for 172.16.192.0/19
  Known via "bgp 65001", distance 20, metric 100
  Tag 65000, type external
  Redistributing via ospf 1
  Advertised by ospf 1 subnets tag 0
  Last update from 169.254.13.109 03:37:09 ago
  Routing Descriptor Blocks:
  * 169.254.13.109, from 169.254.13.109, 03:37:09 ago
      Route metric is 100, traffic share count is 1
      AS Hops 2
      Route tag 65000
      MPLS label: none
      MPLS Flags: NSF

asr1k/dallas#show ip ospf 1 database

            OSPF Router with ID (172.18.255.1) (Process ID 1)

        Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
172.16.255.28   172.16.255.28   358         0x80005070 0x00C976 18
172.17.255.1    172.17.255.1    696         0x8000A4AB 0x003027 18
172.18.255.1    172.18.255.1    344         0x8002933B 0x00B226 23
172.19.255.1    172.19.255.1    1562        0x8000FEE0 0x00553C 22
172.20.255.1    172.20.255.1    762         0x800F04F8 0x00A1D6 23
172.21.255.1    172.21.255.1    1223        0x8002CAA2 0x00DFAF 3
172.22.255.1    172.22.255.1    125         0x8000D829 0x00DD6C 23
172.23.255.1    172.23.255.1    192         0x80004AD5 0x00EFB5 19
172.24.255.1    172.24.255.1    306         0x80006A76 0x0005AF 18
172.25.255.1    172.25.255.1    238         0x8000B51E 0x00B20C 23
172.27.255.1    172.27.255.1    159         0x8000588C 0x000254 19
172.30.255.1    172.30.255.1    1693        0x80001EC0 0x00045E 18
172.31.255.1    172.31.255.1    323         0x8000E561 0x004758 16
172.32.255.1    172.32.255.1    655         0x80003F20 0x00A33F 2

        Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
172.16.253.0    172.25.255.1    2011        0x80003F1C 0x00E1E7

        Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
172.16.192.0    172.18.255.1    597         0x80000003 0x008B87 0
172.17.0.0      172.17.255.1    1461        0x800073C6 0x00CF1B 0
172.18.0.0      172.18.255.1    1881        0x8000739C 0x001003 0
172.19.0.0      172.19.255.1    1066        0x8000736F 0x0056E7 0
172.20.0.0      172.20.255.1    762         0x8000731A 0x00ECA4 0
172.22.0.0      172.22.255.1    1412        0x80007396 0x00CB45 0
172.23.0.0      172.23.255.1    1445        0x80003B75 0x00A2C5 0
172.24.0.0      172.24.255.1    306         0x800052F9 0x00408A 0
172.25.0.0      172.25.255.1    2011        0x80007341 0x003A26 0
172.27.0.0      172.27.255.1    1672        0x80003390 0x003419 0
172.28.0.0      172.16.255.28   601         0x8000442E 0x006F1E 0

And here is the output from a different router:

asr1k/atlanta#show run | sec router ospf 1

router ospf 1 vrf blue
 router-id 172.22.255.1
 ispf
 prefix-suppression
 timers throttle spf 10 100 1000
 timers throttle lsa 10 100 1000
 timers lsa arrival 50
 timers pacing flood 5
 timers pacing retransmission 60
 redistribute static subnets
 passive-interface default
 no passive-interface GigabitEthernet0/0/2.100
 no passive-interface Tunnel1000
 network 172.16.0.0 0.15.255.255 area 0
 neighbor 172.16.254.19
 neighbor 172.16.254.18
 neighbor 172.16.254.25
 neighbor 172.16.254.20
 neighbor 172.16.255.27 cost 5000
 maximum-paths 1

asr1k/atlanta#show ip route vrf blue 172.16.192.0

Routing Table: blue
% Subnet not in table

asr1k/atlanta#show ip ospf 1 database

            OSPF Router with ID (172.22.255.1) (Process ID 1)

        Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
172.16.255.28   172.16.255.28   515         0x80005070 0x00C976 18
172.17.255.1    172.17.255.1    853         0x8000A4AB 0x003027 18
172.18.255.1    172.18.255.1    501         0x8002933B 0x00B226 23
172.19.255.1    172.19.255.1    1718        0x8000FEE0 0x00553C 22
172.20.255.1    172.20.255.1    918         0x800F04F8 0x00A1D6 23
172.21.255.1    172.21.255.1    1380        0x8002CAA2 0x00DFAF 3
172.22.255.1    172.22.255.1    280         0x8000D829 0x00DD6C 23
172.23.255.1    172.23.255.1    347         0x80004AD5 0x00EFB5 19
172.24.255.1    172.24.255.1    462         0x80006A76 0x0005AF 18
172.25.255.1    172.25.255.1    394         0x8000B51E 0x00B20C 23
172.27.255.1    172.27.255.1    314         0x8000588C 0x000254 19
172.30.255.1    172.30.255.1    1849        0x80001EC0 0x00045E 18
172.31.255.1    172.31.255.1    480         0x8000E561 0x004758 16
172.32.255.1    172.32.255.1    811         0x80003F20 0x00A33F 2

        Net Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum
172.16.253.0    172.25.255.1    132         0x80003F1D 0x00DFE8

        Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
172.16.192.0    172.18.255.1    755         0x80000003 0x008B87 0
172.17.0.0      172.17.255.1    1619        0x800073C6 0x00CF1B 0
172.18.0.0      172.18.255.1    1           0x8000739D 0x000E04 0
172.19.0.0      172.19.255.1    1223        0x8000736F 0x0056E7 0
172.20.0.0      172.20.255.1    919         0x8000731A 0x00ECA4 0
172.22.0.0      172.22.255.1    1568        0x80007396 0x00CB45 0
172.23.0.0      172.23.255.1    1601        0x80003B75 0x00A2C5 0
172.24.0.0      172.24.255.1    463         0x800052F9 0x00408A 0
172.25.0.0      172.25.255.1    132         0x80007342 0x003827 0
172.27.0.0      172.27.255.1    1829        0x80003390 0x003419 0
172.28.0.0      172.16.255.28   759         0x8000442E 0x006F1E 0

asr1k/atlanta#show ip ospf 1 database external 172.16.192.0

            OSPF Router with ID (172.22.255.1) (Process ID 1)

        Type-5 AS External Link States

  LS age: 764
  Options: (No TOS-capability, DC, Downward)
  LS Type: AS External Link
  Link State ID: 172.16.192.0 (External Network Number )
  Advertising Router: 172.18.255.1
  LS Seq Number: 80000003
  Checksum: 0x8B87
  Length: 36
  Network Mask: /19
    Metric Type: 2 (Larger than any link state path)
    MTID: 0
    Metric: 1
    Forward Address: 0.0.0.0
    External Route Tag: 0

EDIT

I also tried removing tag 0 on the redistributing router, I have the same behavior in Atlanta.

asr1k/atlanta#show ip ospf 1 database  external 172.16.192.0

            OSPF Router with ID (172.22.255.1) (Process ID 1)

        Type-5 AS External Link States

  LS age: 23
  Options: (No TOS-capability, DC, Downward)
  LS Type: AS External Link
  Link State ID: 172.16.192.0 (External Network Number )
  Advertising Router: 172.18.255.1
  LS Seq Number: 80000001
  Checksum: 0x9D99
  Length: 36
  Network Mask: /19
    Metric Type: 2 (Larger than any link state path)
    MTID: 0
    Metric: 1
    Forward Address: 0.0.0.0
    External Route Tag: 3489667571

asr1k/atlanta# show ip route vrf blue 172.16.192.0

Routing Table: blue
% Network not in table
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2 Answers 2

Reset to default
6

capability vrf-lite is missing under router ospf

This article has a good explanation. Essentially, the command tells OSPF to ignore the DN bit and use the LSA in the SPF calculations.

https://supportforums.cisco.com/discussion/12754196/where-configure-capability-vrf-lite-ce-or-pe

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1
  • This worked. I added this in Atlanta, the router that wasn't installing the route. With or without tag 0 on the redistributing router (Dallas). Can you expand your answer as to explain what capability vrf-lite does and why it's needed?
    – zevlag
    Feb 14, 2017 at 16:05
3

The issue is right here in your database output:

Options: (No TOS-capability, DC, Downward)

At the point of redistribution the Down bit is being set as a loop prevention mechanism. By itself this wouldn't necessarily be a bad thing but you're also clearing the domain tags that are otherwise being set at the point of redistribution. This mechanism is described here and, basically, is such that any downstream ASBR that sees an OSPF entry with that down bit set and an identical or missing domain ID is not going to allow it as an installed route.

In short, it's basically a loop prevention mechanism. Try removing the tag 0 statement from the redistribution on the Dallas router.

It also might be a smart thing to have some kind route-maps on the redistribution to have both an explicit degree of control over what's passing between domains as well as a mechanism to control route attributes/metrics (just one example: type-1's can be really nice for choosing between multiple ASBR's based on IGP, but being able to selectively manipulate metrics based on BGP communities can be worth its weight). This is purely just a hygiene suggestion, though.

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  • I thought this was the case, that's why I tried adding tag 0. After removing it, I have the same behavior. I'll update the question to include that output.
    – zevlag
    Feb 14, 2017 at 15:57

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