6-4 - Troubleshoot PE-to-Route Reflector Flashcards
T/F: Classic IBGP split-horizon rules specify that updates that a router receives on an EBGP session should forward on all IBGP and EBGP sessions. However, updates that a router receives on an IBGP session should forward only to all EBGP sessions.
True
T/F: The primary reason for the IBGP split-horizon rule is to avoid routing information loops within the AS.
True
What is the formula for determining how many iBGP sessions must exist in a true full-mesh design?
(n * (n - 1)) / 2
where n is the number of nodes
T/F: Route reflectors are a BGP scalability mechanism that enables routing information to redistribute to all routers within an AS by eliminating the need for a fully meshed topology.
True
T/F: Route reflectors modify the classic IBGP split-horizon rule and allow a particular router to forward incoming IBPG updates to an outgoing IBGP session under certain conditions.
True
T/F: A route reflector router can reflect routes across multiple clusters.
False. A route reflector router can reflect routes only within a single cluster.
T/F: A route reflector can, however, participate in another cluster, but only as a client.
True
T/F: A client can function as a client only to a route reflector that belongs to the same cluster.
True
T/F: The cluster-list and originator-ID attributes are nontransitive optional BGP attributes.
True
Based on cluster-list and originator-ID attributes, routers can implement two loop-prevention mechanisms:
- Any router that receives an IBGP update with the originator-ID attribute set to its own BGP router-ID will ignore that update.
- Any router reflector that receives an IBGP update with its cluster-ID already in the cluster-list will ignore that update.
BGP path selection rules are modified to select the best route in scenarios where a router might receive reflected routes:
- The traditional BGP path selection parameters, such as weight, local preference, origin, and MED, are compared first.
- If these parameters are equal, the routes that are received for EBGP neighbors are preferred over routes that are received from IBGP neighbors.
- When a router receives two IBGP routes, the nonreflected routes (routes with no originator-ID attribute) are preferred over reflected routes.
- The reflected routes with shorter cluster-lists are preferred over routes with longer cluster-lists.
- If the additional route-reflector-oriented selection criteria do not yield a decision, the rest of the traditional BGP path selection rules are followed.
What is this a configuration of?
router bgp 1
bgp cluster-id 175
address-family ipv4 unicast
address-family vpnv4 unicast
neighbor 1.0.0.3
remote-as 1
address-family ipv4 unicast
route-reflector-client
address-family vpnv4 unicast
route-reflector-client
neighbor 1.0.0.4
remote-as 1
address-family ipv4 unicast
route-reflector-client
address-family vpnv4 unicast
route-reflector-client
This is an example configuration of a route reflector in BGP with neighbors defined as route-reflector clients and a defined BGP cluster-id.
T/F: All clients in a cluster should have IBGP sessions with all their route reflectors. A client must have sessions with all the reflectors in the cluster to avoid violating the redundancy. If a client has IBGP sessions to routers other than route reflectors, unnecessary routing traffic generates.
True
How does the route reflector scalability mechanism work?
A. Route reflectors modify the classic IBGP split-horizon rule.
B. A router that acts as a route reflector client requires a specific configuration.
C. Route reflectors increase the number of TCP sessions that the system must maintain.
D. The route reflector forwards EBGP updates to all its clients.
A
