Linux, FreeBSD, Juniper, Cisco / Network security articles and troubleshooting guides

FAQ
It is currently Sat Aug 19, 2017 2:43 am


Author Message
mandrei99
Post  Post subject: Injecting a default route in an OSPF NSSA area from a Juniper device  |  Posted: Sun Mar 15, 2015 5:24 pm

Joined: Tue Aug 04, 2009 9:16 am
Posts: 245

Offline
 

Injecting a default route in an OSPF NSSA area from a Juniper device

OSPF not-so-stubby area is described in RFC 3101 (https://tools.ietf.org/html/rfc3101) and it’s main characteristics are that it does not accept OSPF external LSAs (Type 5) as a stubby area, but it allows injection of AS external prefixes, as a normal area. It makes use of Type 7 LSAs that get translated into Type 5 External LSAs by the ABR into the rest of the OSPF domain. Section 1.3 of the RFC describes NSSA areas better than I can ever try :).

A default route in an not-so-stubby OSPF area can result either from a Type 3 LSA or from a Type 7 LSA.

JunOS: How to inject a default route into an NSSA area with a Type - 3 Summary LSA


To inject a default route from a Juniper device which is an ABR into a not so stubby area, Junos needs to actually have “no-summaries” configured. This will prevent other Type 3 Summaries to go into the NSSA area with the exception of a “0.0.0.0” Summary. From the ABR:

Code:
@hub-vSRX1# show protocols ospf
area 0.0.0.1 {
    nssa {
        default-lsa {
            default-metric 1;
            metric-type 1;
        }
        no-summaries;
    }
    interface st0.0 {
        interface-type p2p;
    }
    interface st0.1 {
        interface-type p2p;
    }
}

and the result in OSPF database:
Code:
@spoke-vSRX2# run show ospf database

    OSPF database, Area 0.0.0.1
Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Router   172.16.255.1     172.16.255.1     0x80000097  1256  0x20 0x7cfe  72
Router  *172.16.255.2     172.16.255.2     0x800000a0  1256  0x20 0x6516  84
Summary  0.0.0.0          172.16.255.1     0x80000002   100  0x20 0x1768  28
NSSA    *8.0.0.0          172.16.255.2     0x80000038   811  0x28 0xf17a  36


See the default LSA is a Summary LSA.

JunOS: How to inject a default route into an NSSA area with a Type - 7 NSSA LSA


On the ABR:
Code:
admin@hub-vSRX1# set protocols ospf area 1 nssa default-lsa type-7

[edit]
admin@hub-vSRX1# commit
commit complete


And the result:
Code:
[edit]
admin@spoke-vSRX2# run show ospf database

    OSPF database, Area 0.0.0.1
Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Router   172.16.255.1     172.16.255.1     0x80000097  1311  0x20 0x7cfe  72
Router  *172.16.255.2     172.16.255.2     0x800000a0  1311  0x20 0x6516  84
Summary  0.0.0.0          172.16.255.1     0x80000002  3600  0x20 0x1768  28
NSSA     0.0.0.0          172.16.255.1     0x80000001     2  0x20 0xf083  36
NSSA    *8.0.0.0          172.16.255.2     0x80000038   866  0x28 0xf17a  36

The default Summary LSA gets aged out (age 3600) and a new default NSSA LSA is generated by the ABR.


To note here:
“no-summaries” disables Type 3 Summary LSAs the NSSA with the exception of default one. This turns the area practically into a NSSA totally stub area.
“Type-3” is default type for the default LSA into a NSSA area when "no-summaries" is set. If "no-summaries" is left out, it is injected as a Type-7.
The ABR needs an area 0 adjacency in order to inject a default route into the NSSA area.

Juniper official documentation: https://www.juniper.net/documentation/en_US/junos14.1/topics/topic-map/ospf-stub-and-not-so-stubby-areas.html.
Please comment.





Top
Display posts from previous:  Sort by  
E-mail friendPrint view

Topics related to - "Injecting a default route in an OSPF NSSA area from a Juniper device"
 Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Attachment(s) OSPF: Dangers of non-standard area design - Juniper way

mandrei99

0

879

Thu Nov 13, 2014 12:29 pm

mandrei99 View the latest post

There are no new unread posts for this topic. OSPF Multi area scenario with isolated areas cisco & Juniper - part 1.

mandrei99

0

1202

Thu Nov 13, 2014 9:51 am

mandrei99 View the latest post

There are no new unread posts for this topic. Understanding the OSPF External NSSA LSA Metric Type 1 with JunOS examples

mandrei99

0

1464

Sun Mar 15, 2015 1:51 pm

mandrei99 View the latest post

There are no new unread posts for this topic. How to configure Junos ipv6 default route

mandrei99

0

2982

Mon Feb 16, 2015 6:29 pm

mandrei99 View the latest post

There are no new unread posts for this topic. Example of BGP update message sent from Junos device when export policy is modified

mandrei99

0

575

Fri Jul 19, 2013 9:09 am

mandrei99 View the latest post

There are no new unread posts for this topic. OSPF areas - how to achieve optimal routing - Cisco way

mandrei99

1

834

Tue Nov 25, 2014 8:46 pm

Exsosus View the latest post

There are no new unread posts for this topic. Attachment(s) OSPF areas: Analysing an apprently redundant design - Cisco way

mandrei99

0

719

Tue Nov 18, 2014 11:14 am

mandrei99 View the latest post

There are no new unread posts for this topic. OSPF neighbors stuck in ExStart - case 1 - interface type mismatch

mandrei99

0

3845

Wed Dec 10, 2014 5:42 am

mandrei99 View the latest post

There are no new unread posts for this topic. Attachment(s) Twisted LDP signaled VPLS scenario using Juniper SRX selective packet services

mandrei99

1

1456

Mon Apr 13, 2015 3:25 am

Tripple26 View the latest post

 

Who is online
Users browsing this forum: No registered users and 0 guests
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum
Jump to:  
News News Site map Site map SitemapIndex SitemapIndex RSS Feed RSS Feed Channel list Channel list


Delete all board cookies | The team | All times are UTC - 5 hours [ DST ]



phpBB SEO