Routing
Routing

OSPF summary routes in Hub & Spoke

‎04-03-2013 05:57 AM

Hi Experts
Could you please help regarding the below scenario.

In the hub and spoke topology shown in the uploaded diagram, S2 which is running OSPF is advertising the external route 129.168.4.0/24 and the summary 192.168.4.4/32.

No changes in the domain-id value between R5 and R1 in order to keep the summary route as is.
On R1 the routes are imported in the Spoke vrf which imports all spokes routes and exports null.
The OSPF under this vrf is this configured with domain-vpn tag 0 to allow the hub CE which receives the 2 routes to redistribute the external route back to the hub vrf on R1.

The hub vrf is responsible of advertising the routes to the rest of spoke sites.

 

The question is why unlike the external route, the summary is not showing on the hub vrf table although it is present in hub database and how caw overcome this issue ?

 

Below are the o/p showing this behavior.

 

root@R1# run show route table hub 192.168.2.2/32


root@R1# run show route table hub 192.168.2.0/24

hub.inet.0: 10 destinations, 10 routes (10 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

192.168.2.0/24     *[OSPF/150] 01:13:33, metric 0, tag 0
                    > to 172.27.0.134 via ge-0/0/0.300


root@R1# run show route table hub 192.168.2.2      

hub.inet.0: 12 destinations, 12 routes (12 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

192.168.2.0/24     *[OSPF/150] 01:13:36, metric 0, tag 0
                    > to 172.27.0.134 via ge-0/0/0.300

 
root@R1# run show OSPF database instance hub

    OSPF database, Area 0.0.0.0
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Router   172.27.0.33      172.27.0.33      0x8000000f  1875  0x22 0x3944  36
Router  *172.27.0.133     172.27.0.133     0x8000000f  1325  0x22 0x5697  36
Router   192.168.0.254    192.168.0.254    0x80000014  2373  0x22 0x1a3a  60
Network  172.27.0.34      192.168.0.254    0x8000000d  1770  0x22 0x117c  32
Network  172.27.0.134     192.168.0.254    0x8000000f   572  0x22 0x9e24  32
Summary  192.168.2.2      172.27.0.33      0x80000005  1207  0xa2 0x76ea  28
    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Extern   172.27.0.48      172.27.0.33      0x80000009   873  0x22 0x418b  36
Extern   172.27.0.64      172.27.0.33      0x80000003  1542  0x22 0xac16  36
Extern   172.27.0.72      172.27.0.33      0x80000009   539  0x22 0x5064  36
Extern   192.168.0.0      192.168.0.254    0x80000005  1171  0x22 0x419b  36
Extern   192.168.2.0      172.27.0.33      0x80000005   181  0x22 0x7fda  36
Extern   192.168.4.0      172.27.0.33      0x800004a0  3600  0x22 0x2692  36
Extern   192.168.4.4      172.27.0.33      0x800004a0  3600  0x22 0xfdb6  36

 

 

Best Regards

Bassem Wahba

Bassem Wahba

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Routing

Re: OSPF summary routes in Hub & Spoke

‎04-03-2013 07:30 AM

Use "domain-id  disable" under vrf ospf hierarchy in order to clear D/N bit (0xa2 ) 

 

 

Best Regards,

Krasi