Getting JN0-664 Certification Made Easy!

To transport IPv6 traffic over an IPv4-based MPLS network using BGP, you need to configure two address families: family inet6 labeled-unicast and family inet6 unicast. The former is used to exchange IPv6 routes with MPLS labels between PE routers, and the latter is used to exchange IPv6 routes without labels between PE and CE routers. The mpis ipv6-tunneling command enables the PE routers to encapsulate the IPv6 packets with an MPLS label stack and an IPv4 header before sending them over the MPLS network.

VPLS is a Layer 2 VPN technology that allows multiple sites to connect over a shared IP/MPLS network as if they were on the same LAN. VPLS tunnels can be signaled using either Label Distribution Protocol (LDP) or Border Gateway Protocol (BGP). LDP-signaled VPLS tunnels use auto-discovery to provision sites, meaning that PE routers can automatically discover other PE routers that belong to the same VPLS instance

BGP GTSM is a technique that protects a BGP session by comparing the TTL value in the IP header of incoming BGP packets against a valid TTL range. If the TTL value is within the valid TTL range, the packet is accepted. If not, the packet is discarded. The valid TTL range is from 255 – the configured hop count + 1 to 255. When GTSM is configured, the BGP packets sent by the device have a TTL of 255. GTSM provides best protection for directly connected EBGP sessions, but not for multihop EBGP or IBGP sessions because the TTL of packets might be modified by intermediate devices.

In the exhibit, we can see that R2, R3, and R4 are in the same AS (AS 20) and R1 is in a different AS (AS 10). Based on this information, we can infer the following statements:

• You can implement BGP GTSM between R2, R3, and R4. This is not correct because R2, R3, and R4 are IBGP peers and GTSM does not provide effective protection for IBGP sessions. The TTL of packets between IBGP peers might be changed by intermediate devices or routing protocols.
• BGP GTSM requires a firewall filter to discard packets with incorrect TTL. This is not correct because BGP GTSM does not require a firewall filter to discard packets with incorrect TTL. BGP GTSM uses TCP option 19 to negotiate GTSM capability between peers and uses TCP option 20 to carry the expected TTL value in each packet. The receiver checks the expected TTL value against the actual TTL value and discards packets with incorrect TTL values.
• You can implement BGP GTSM between R2 and R1. This is correct because R2 and R1 are EBGP peers and GTSM provides effective protection for directly connected EBGP sessions. The TTL of packets between directly connected EBGP peers is not changed by intermediate devices or routing protocols.
• BGP GTSM requires a TTL of 1 to be configured between neighbors. This is not correct because BGP GTSM requires a TTL of 255 to be configured between neighbors. The sender sets the TTL of packets to 255 and the receiver expects the TTL of packets to be 255 minus the configured hop count.
• BGP GTSM requires a TTL of 255 to be configured between neighbors. This is correct because BGP GTSM requires a TTL of 255 to be configured between neighbors. The sender sets the TTL of packets to 255 and the receiver expects the TTL of packets to be 255 minus the configured hop count.

To allow Site 1 to access three VLANs that are located in Site 2 and Site 3, you need to configure three L2VPN routing instances on PE-1, one for each VLAN. Each L2VPN routing instance will have a different VLAN ID and a different VNI for VXLAN encapsulation. Each L2VPN routing instance will also have a different vrf-target export value to identify which VPN routes belong to which VLAN. This way, PE-1 can forward traffic from Site 1 to Site 2 and Site 3 based on the VLAN tags and VNIs.

The sequence number is a field in the MAC mobility extended community that is used to resolve conflicting MAC address ownership claims and to help the local PE to identify the latest advertisement. The sequence number is incremented by one for every MAC address mobility event, such as when a host moves from one Ethernet segment to another segment in the EVPN network. The PE device that receives multiple MAC advertisements for the same MAC address chooses the one with the highest sequence number as the most recent and valid advertisement.