[j-nsp] PE-CE issue with OSPF routes not getting into routing table

[Jayaraj Shantharam]

Hi, I did not read this mail. The dn bit is set indicating routing loop Regards, Jay 



From: Krasimir Avramski <krasi at smartcom.bg>
Sent: Sun, 26 Aug 2018 14:47:33 GMT+0530
To: "Raymond, Adam" <Adam.Raymond at nextgengroup.com.au>
Subject: Re: [j-nsp] PE-CE issue with OSPF routes not getting into routing table

Hi,



The route from your output has DN bit set (Opt 0xa2) and it is loop

prevention mechanism as described in rfc4577.



More info from Juniper docs:

http://www.juniper.net/techpubs/en_US/junos12.2/topics/usage-guidelines/vpns-configuring-routing-between-pe-and-ce-routers-in-layer-3-vpns.html



Best Regards,

Krasi



On Sun, Aug 26, 2018, 05:19 Raymond, Adam via juniper-nsp <

juniper-nsp at puck.nether.net> wrote:



> Hi,

>

>         Complex one, so I will try to describe this carefully.

>

>         I have a IPv4 layer 3 MP-BGP VPN. There are two PEs that have an

> OSPF adjacency to CEs inside the VPN. The VPN only has a single OSPF area:

> 0.0.0.0. An external route, 172.16.64.0/20, is inserted into the VPN

> (called IP_ASC_VPN_1) via redistribution from iBGP and into OPSF.

>         The slightly odd thing about this setup compared to a traditional

> VPN is that the PEs have devices connected to them that don't support

> dynamic routing - they are just node with a IP address and default gateway

> configured on them:

>

>   PE3 -- CE5

>   |

>   P --------------------------------------------------------------P

>   |                                                               |

>   P -- PE1 --OSPF-- CE1 --OSPF-- CE2 --OPSF-- CE3 --OSPF-- PE2 -- P

>         |                                                   |

>        Node                                                Node

>

> All of this works when all of the network is up and operational, but when

> the link from the P routers to the PEs breaks:

>   PE3 -- CE5

>   |

>   P --------------------------------------------------------------P

>   |                                                               |

>   P -X- PE1 --OSPF-- CE1 --OSPF-- CE2 --OPSF-- CE3 --OSPF-- PE2 -- P

>          |                                                   |

>         Node                                                Node

>

> Then the Node closest to the break becomes unreachable from CE5. CE5 is

> also the router that inserts 172.16.64.0/20 into the VPN. I can log into

> PE1 by jumping from CE1 and see what is happening on that router. PE1 is

> still learning the 172.16.64.0/20 route via OSPF as you can see it in the

> OSFP database:

> araymond at PE1> show ospf database external extensive lsa-id 172.16.64.0

> instance IP_ASC_VPN_1

>     OSPF AS SCOPE link state database

>  Type       ID               Adv Rtr           Seq      Age  Opt  Cksum

> Len

> Extern   172.16.64.0      172.16.49.68     0x80000001   192  0xa2 0xf2f1

> 36

>   mask 255.255.240.0

>   Topology default (ID 0)

>     Type: 2, Metric: 3000, Fwd addr: 0.0.0.0, Tag: 208.0.255.152

>   Aging timer 00:56:47

>   Installed 00:03:06 ago, expires in 00:56:48

>   Last changed 00:03:06 ago, Change count: 1

>

> where 172.16.49.68 is the router-id of PE2.

>

> The problem is that this route doesn't get added to the

> IP_ASC_VPN_1.inet.0 routing table. There seems to be something that makes

> this route ineligible, but I cannot figure out what it is. Can anyone help

> me with that?

>

> Regards,

>

> Adam Raymond | IP Platform Engineering Team Lead

>

> M: 0410 347 012   D: 03 8623 3638 | ext   E: Adam.Raymond at vocus.com.au

> <mailto:Adam.Raymond at vocus.com.au>

> P: +61 3 8613 3333  W: vocus.com.au

> A: 333 Collins Street, Melbourne, VIC 3000, Australia  |  Follow us:

>

>

>

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