MPLS - InterAS L3VPN and CsC

Question 1

In option B the session between the ASBRs needs to be label unicast

Answer 1

False, the session must have the AF VPNv4

Question 2

In option B, there are two designs “next-hop unchanged” and “next-hop self”

Answer 2

True

Question 3

In option B by default an ASBR is also considered a PE, so the VRF must exist locally for VPN prefixes to be imported into the BGP table and into the FIB.

Answer 3

False, for scalability reasons the ASBR is not a PE therefore there is no VRF, for this reason by default VPNv4 routes will not be imported, so the command “no bgp default route-target filter” must be applied

Question 4

In option B, in the “next-hop unchanged” design, the PEs do not need to have a /32 route to the remote ASBR, as long as the uplink between the ASBRs is within the PEs’ RIB and there is a label associated

Answer 4

False. In option B, in the “next-hop unchanged” design, the PEs must have a /32 route to the remote ASBR, normally the ASBR creates this route automatically as connected and it must be redistributed in the IGP

Question 5

In option C the ASBRs exchange VPNV4 prefixes

Answer 5

False, only the RRs exchange

Question 6

In option C the RRs operate by default

Answer 6

False, it must be ensured that the RRs do not alter the next-hop attribute, this is default in iBGP sessions but not in eBGP sessions, additionally multihop is necessary

Question 7

In option C the reachability of the PEs’ loopbacks must be provided via BGP IPV4 + label announcement exchanged between the ASBRs

Answer 7

True

Question 8

For CsC the basic requirement is that the CE and PE exchange MPLS labels

Answer 8

True

Question 9

Resource that allows using the same routing protocol to exchange conflicting/overlapping prefixes

Answer 9

Routing context

Question 10

___ ____________ • Additional feature that allows identifying the VPN • Useful for applications like Radius o Radius can define that dial-in users belong to the VPN

Answer 10

VPN Identifier

Question 11

In IOS XR the propagation of ext comm is automatic

Answer 11

True

Question 12

__________ is established between the loopbacks of the PEs, these /32 must be announced via BGP and not OSPF to avoid flaps due to the AD difference iBGPxOSPF

Answer 12

• The sham link

Question 13

What command configures a sham-link?

Answer 13

area 0 sham-link {{Local Loopback}} {{Remote Loopback}}

Question 14

OSPFv3 as PE-CE • In IOS__ supports only ipv6 and is VRF Aware • In IOS__ supports ipv4 and ipv6 and is vrf Aware

Answer 14

XR, XE

Question 15

• To carry OSPF attributes other extended communities were created. • __________ o Indicates whether a route should be advertised as external o Set by default equal to the OSPF process number o If the domain ID of the PEs is different the routes will be exchanged as external by default  To avoid problems configure the OSPF Process of the VRF with the same number or set the Domain ID manually  A type ___ route is an external route

Answer 15

The Domain ID, Type 5

Question 16

• In OSPF Value set in the options field and indicates the direction in which the route was advertised

Answer 16

Down bit. o PE > CE direction down

Question 17

In OSPF • Has the same purpose as the down bit, but for external routes • _________ can be configured manually • If a PE receives a route marked with the domain tag the route is not redistributed

Answer 17

The domain tag can be configured manually • If a PE receives a route marked with the domain tag the route is not redistributed

Question 18

In EIGRP as a PE - CE protocol the ASN needs to be defined only once for the global process, the specific context of the customer’s VRF will inherit this configuration

Answer 18

False

Question 19

Normally tags would be used to prevent but in an MPLS environment this may not work properly. The Communities _________ is a feature that allows adding these communities to updates ____ and ____

Answer 19

Site-of-Origin, BGP and EIGRP

Question 20

SOO communities must be configured directly on the uplink interfaces

Answer 20

True, but it depends on the OS and implementation, it can be at the interface or process level router eigrp 90 vrf EIGRP address-family ipv4 {…} interface GigabitEthernet0/0/0/2.90 site-of-origin 90:12 IOSXE R1#show running-config | se route-map route-map set-soo-13 permit 10 set extcommunity soo 90:13 interface GigabitEthernet3.90 ip vrf sitemap set-soo-13 router bgp 1 address-family ipv4 vrf CUSTOMER_A neighbor 10.0.1.2 site-of-origin 65002:1

Question 21

BGP as PE CE - By default routes learned from the same AS will be accepted, what are the 3 solutions that can be applied

Answer 21

AS Override, Allow AS IN, eBGP sessions - Each site in one AS

Question 22

What command is equivalent to no bgp default route-target filter

Answer 22

Command retain route-target all router bgp 11 bgp router-id 11.0.255.17 address-family vpnv4 unicast retain route-target all ! address-family vpnv6 unicast retain route-target all