Last Updated on July 31, 2021 by Admin 1
Consider the following output of the show ip bgp summary command:
Which of the following neighbors have an established connection with RouterA?
- 10.1.1.1
- 10.2.1.1
- 10.3.1.1
- 10.4.1.1
- 10.5.1.1
Explanation:
The neighbor with the IP address 10.2.1.1 has an established connection with RouterA. This is because the State/PfxRcd value for this neighbor is a number, 15, which indicates the number of prefixes received by RouterA from the neighbor. The prefixes are exchanged between BGP neighbors through the update message, which can be transmitted only if an established connection exists between the neighbors. An established connection exists between two neighbors if the local router is in Open Confirm state and it receives a KEEPALIVE or an UPDATE message.The connection between RouterA and the neighbor with the IP address 10.1.1.1 is not established. This is because the State/PfxRcd value for this neighbor is OPENSENT. In this state, RouterA sends an OPEN message to a neighbor to determine the parameters for establishing a connection. The OPENSENT state occurs before the connection is established.The connection between RouterA and the neighbor with the IP address 10.3.1.1 is not established. This is because the State/PfxRcd value for this neighbor is IDLE. In this state, RouterA does not accept any incoming connections from the neighbor.The connection between RouterA and the neighbor with the IP address 10.4.1.1 is not established. This is because the State/PfxRcd value for this neighbor is ACTIVE. In this state, RouterA is attempting to establish a BGP peering session but it is not yet complete.The connection between RouterA and the neighbor with the IP address 10.5.1.1 is not established. This is because the State/PfxRcd value for this neighbor is OPENCONFIRM. In this state, RouterA waits for a KEEPALIVE or NOTIFICATION message from the neighbor.
The neighbor with the IP address 10.2.1.1 has an established connection with RouterA. This is because the State/PfxRcd value for this neighbor is a number, 15, which indicates the number of prefixes received by RouterA from the neighbor. The prefixes are exchanged between BGP neighbors through the update message, which can be transmitted only if an established connection exists between the neighbors. An established connection exists between two neighbors if the local router is in Open Confirm state and it receives a KEEPALIVE or an UPDATE message.The connection between RouterA and the neighbor with the IP address 10.1.1.1 is not established. This is because the State/PfxRcd value for this neighbor is OPENSENT. In this state, RouterA sends an OPEN message to a neighbor to determine the parameters for establishing a connection. The OPENSENT state occurs before the connection is established.The connection between RouterA and the neighbor with the IP address 10.3.1.1 is not established. This is because the State/PfxRcd value for this neighbor is IDLE. In this state, RouterA does not accept any incoming connections from the neighbor.The connection between RouterA and the neighbor with the IP address 10.4.1.1 is not established. This is because the State/PfxRcd value for this neighbor is ACTIVE. In this state, RouterA is attempting to establish a BGP peering session but it is not yet complete.The connection between RouterA and the neighbor with the IP address 10.5.1.1 is not established. This is because the State/PfxRcd value for this neighbor is OPENCONFIRM. In this state, RouterA waits for a KEEPALIVE or NOTIFICATION message from the neighbor.
Objective:
Layer 3 Technologies
Sub-Objective:
Describe, configure, and verify BGP peer relationships and authentication