Advanced OSPF - Route Filtering

5 important questions on Advanced OSPF - Route Filtering

What three techniques are there for filtering OSPF routes?

1. Filtering with Summarization
2. Area Filtering
3. Local OSPF Filtering

How can summarization be used for Route Filtering?

By using the not-advertise option in the summary command there won't be any Type 3 LSAs created for any networks in that range.

How does OSPF Area Filtering work and when is it used?

Each ABR functions as a kind of filter/firewall within OSPF.
deny/permit lists can be created and added in the OSPF process.
The ABR can filter either inbound or outbound from and to an area.
It is used for filtering between areas.
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What is the command Distribute-list used for in OSPF?

The Distribute-List function prevents a route to be installed in the Routing Table of the local router.
It can be seen as Local OSPF Filtering.
The full command is:
distribute-list {acl-number | Acl-name | Prefix prefix-list | Route-map route-map} In

What is the command Distribute-list used for in OSPF?

The Distribute-List function prevents a route to be installed in the Routing Table of the local router.
It can be seen as Local OSPF Filtering.
The full command is:
distribute-list {acl-number | Acl-name | Prefix prefix-list | Route-map route-map} In

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