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The OSPF Instance Failed to Advertise Default Routes on a Non-Mandatory Basis in the NE40

Publication Date:  2012-07-27 Views:  37 Downloads:  0
Issue Description
Eudemon-1----------------E-2
|                          |
|                          |
NE40-1--vlan 3 ospf 100----NE40-2
|                          |
|                          |
Switch 1-----------------Switch 2
Eudemon-1 (10.20.159.6)
NE40-1 and NE40-2 advertise default routes on a non-mandatory basis simultaneously.
A static default route is configured on NE40-1, directed to Eudemon-1. No static default route or other types of default routes are configured on NE40-2.
The interfaces of the two routers are all in IP binding VPN-instance MSS.
The running OSPF100, area 0, and neighbors are all in the Full state.
The default routes advertised by NE40-1 cannot be seen on NE40-2.
NE40-1:
ospf 100 vpn-instance MSS
default-route-advertise type 1
filter-policy 2000 import
import-route static tag 100
import-route bgp
silent-interface LoopBack1001
spf-schedule-interval 1
area 0.0.0.0
network 10.20.159.0 0.0.0.3
network 10.20.159.4 0.0.0.3
network 10.20.159.12 0.0.0.3
network 10.20.159.20 0.0.0.3
network 10.20.159.254 0.0.0.0
network 10.20.159.8 0.0.0.3 
                  AS External Database                                          
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric      
 External  0.0.0.0         10.20.159.254     1135  36    80000022       1
NE40-2:
<ZJDCN-HW-NE40-8-HB-RU2>disp ospf 100 lsdb does not contain information about default routes. 
                  AS External Database                                          
 Type      LinkState ID    AdvRouter          Age  Len   Sequence   Metric      
 External  10.2.255.40     10.20.159.253     1673  36    8000088F     100       
 External  10.20.105.224   10.20.159.253       15  36    80000161       2 

 
Alarm Information
Null
Handling Process
Change the VPN route tags on the two devices so that the tags are different. However, such a change disables the function of the VPN route tags for preventing loops from occurring. 

 
Root Cause
It is confirmed that OSPF may advertise default routes upon the default-route-advertise command to implement load balancing for the preceding networking. The problem arises when the VPN instance advertises OSPF default routes. Therefore, the problem is probably caused by the route tags. In multiple OSPF instances, Type 5 LSAs generated on the PE carry VPN route tags. When the default routes are advertised by NE40-1 to NE40-2, because the tags carried by LSA are the same as the VPN route tags of the local OSPF instances, the routes are not calculated. 

 
Suggestions
Null

END