Introduction to D-link Router Network Protocol BGP

BGP is the only protocol used to process networks like the Internet. It is also the only protocol that can properly handle multi-channel connections between related routing domains, all BGP routes are maintained in the router's BGP routing table. The network accessibility information includes the information of the listed Autonomous Systems, this information effectively constructs the topology of the AS interconnection, removes the routing loop, and implements policy decision-making at the AS level.

1. BGP uses some mechanisms to prevent appeal issues. Automatic route filtering on routers may receive unnecessary route information. Therefore, we hope to filter the IBGP route updates received by the router at the ingress. The automatic route filtering feature meets the filtering requirements. When the router receives the rt value of the ibgp route, the router discards it to reduce the amount of information that needs to be stored in the memory. All routers enable this feature by default without any additional configuration.

2. If the router acts as a route reflector for other routers at the same time, or the Peer of the router as a MP-EBGP needs to exchange cross-domain VPN Information, We need to disable this feature, use the command: no bpg default router-filter BGP Route refresh. Because the automatic route filtering function is enabled on the vro, when the configuration of the vro changes, for example, if a new VRF is added or the existing VRF is deleted, the router's requirements for VPN routing may not be met in a timely manner. Therefore, BGP provides a routing refresh mechanism to achieve this goal.

3. When this feature is used, after a short period of time after the configuration is changed, the router will require its IBGP neighbor to re-Send the route update to obtain the lost VPN-IPv4 information, the router will send a route refresh request to all PE neighbors. The route refresh and Automatic route filtering mechanisms can reduce the number of route information that the router needs to maintain, however, useless routing information is still transmitted in the network, but is discarded after arriving at a specific router.

4. In order to avoid waste of network resources, BGP provides the read/write feature to notify its neighbors of their inbound route filters, this allows unnecessary route information to be filtered out before arriving at the receiver router. The OPEN message is used to exchange the OPEN message in the session creation phase of the two routers, separate IBGP sessions between vrouters. Each vro only needs to receive the VPN route of their services.

Therefore, the mpls vpn network can route different routers into an independent IBGP Cluster Based on Different VPN service objects, and the routers in the same cluster establish full mesh IBGP sessions.