What is a NULL 0 route?
A null interface is a virtual interface that discards IP packets and is used to prevent routing loops from occurring in the network. You do not assign the null interface an IP address. Instead, you create a static route for a network and set the next hop to the null interface (null0).
What is the use of null route in BGP?
A null route means ‘drop this traffic. ‘ One reason to use a null route is for security, but you can also use it for this trick for BGP. The first time people see this, they always think “wait I don’t want to do that, it’s going to drop all of my traffic going to those networks!” But it won’t actually drop the traffic.
Can a black hole route prevent routing loops?
To prevent the routing loops, you can configure a 32-bit-mask blackhole route bound for addresses in the address pool on the NGFW. The NGFW discards packets whose destination addresses match the blackhole route.
What is null route in BGP?
A null route means ‘drop this traffic. ‘ One reason to use a null route is for security, but you can also use it for this trick for BGP.
What is CIDR notation?
CIDR notation (Classless Inter-Domain Routing) is an alternate method of representing a subnet mask. It is simply a count of the number of network bits (bits that are set to 1) in the subnet mask. The CIDR number is typically preceded by a slash “/” and follows the IP address. For example, an IP address of 131.10.
Can a blackhole route prevent routing loops?
The other reason for using null 0 routes in BGP is when BGP network statement uses the mask option then the exact prefix of the network statement must appear in the IP routing table (same address and same mask length). A static route to null 0 may be the easy way to be sure that an exact match will be found in the IP routing table.
How to send the default route to a BGP neighbor?
Another way of advertising a default route to a specific BGP neighbor is by issuing the neighbor default-originate command. This method does not require the presence of the 0.0.0.0/0 network in the routing table of the advertising router.
What’s the difference between BGP and route aggregation?
On the originating router, the aggregated prefix sets the next-hop to Null 0. The route to Null 0 is automatically created by BGP as a loop-prevention mechanism. In both methods of route aggregation, a new network prefix with a shorter prefix length is advertised into BGP.
Why does R3 not include the BGP communities?
R3’s aggregate route (summary) does not include the BGP communities (including AS-Path history) for the routes in the summarization range. R3 advertises the aggregate route to R1 and R2, and those routers install the 172.16.0.0/22 summary route because their AS-Path is not listed in the AS-Path attribute and passes the AS-Path loop check.