BGP prefix filtering mismatch between peers

BGP Prefix Filtering Mismatch Between Peers

Border Gateway Protocol (BGP) is a routing protocol used to exchange routing information between autonomous systems (AS) on the Internet. It is the protocol used by ISPs to interconnect and exchange traffic. To ensure the security of each AS, BGP prefix filtering is used to control the flow of traffic between systems.

When two autonomous systems are connected, they must agree on which routes to accept and which routes to drop. This is done through a process called BGP prefix filtering. Each AS will make a list of prefixes that it will accept and announce to its peers. If a prefix is not in the list, then it will be dropped. This ensures that no malicious traffic can enter the AS.

However, if the two ASs have different lists of prefixes, then there will be a mismatch between the two. The mismatch occurs when the two ASs have different policies regarding which prefixes to accept and announce. As a result, traffic will not be routed between the two ASs.

To resolve this issue, it is important to ensure that the two ASs have identical prefix lists. This can be done by manually setting up the filters or by using a BGP filter synchronization tool.

Manual configuration can be time consuming and error prone. It requires a lot of knowledge about BGP and the network. It also requires a lot of time and effort to set up and maintain the filters.

Using a BGP filter synchronization tool is the easiest and most efficient way to configure the filters. This tool will automatically synchronize the filters between the two ASs, ensuring that they have the same list of prefixes. This reduces the effort and time required to manually configure the filters.

Once the filters are synchronized, traffic will be routed between the two ASs as expected. This eliminates the mismatch between the two ASs and ensures that the network remains secure.

In conclusion, when two autonomous systems are connected, it is important to ensure that they have identical prefix lists. This can be done manually or with a BGP filter synchronization tool. Doing so will ensure that the network remains secure and that traffic is routed as expected between the two ASs.