DMVPN Phase 1 BGP Routing

[lagapidis (Lazarus Agapidis)]

Hello Pradyumna

The Null0 route in routing tables can be used for various reasons. The following posts should cover most of what you are looking for:

Cisco IOS Syslog Messages

Hello Allal The Null0 route is used for various reasons in the routing table. Any routing entry that has an exit interface of Null0 will drop packets to that destination. Using Null0 you are explicitly stating that any packets destined to this specific destination will be dropped. Null0 interfaces in the routing table are used for various reasons. One of the most common is when EIGRP summerization is enabled. EIGRP will advertise a summary route to other routers, but at the same time, will …

How to configure EIGRP Summarization

Hello Olivier Looking at R1, it has two directly connected networks 172.16.0.0/24 and 172.16.1.0/24. You have created a summary route using the 172.16.0.0/23 summary, and this summary route must be placed in the routing table. Where should it send such traffic? Since the directly connected routes will take care of any traffic destined for them, since their AD is 0, the 172.16.0.0/23 route must route somewhere. It is set to route to Null0, in other words drop any packets. In such a situati…

How to configure OSPF Summarization

Hello Saif A summary will be advertised only if there is a subnet that is included within the summary. If that does not exist, then the summary route will not be installed, and no summary LSAs will be sent. Also, no Null0 route will be placed in the routing table. So in this case, the no discard-route internal command would be meaningless. Now if you have a destination within the summary that has been configured, then a Null0 route will be installed in the routing table and summary LSAs wil…

If you have any more specific questions, let us know!

I hope this has been helpful!

Laz