Ericsson Updated ECP-206 Exam Questions and Answers by zak

A label-edged router (LER) is a PE router. A PE router is a provider edge router, which is a router that connects an MPLS network to a customer network. A LER is a term used in MPLS to describe a router that resides at the ingress and egress points of an MPLS network, handling both labelled and unlabelled packets. A LER performs label operations such as adding, removing, or swapping labels on packets entering or leaving the MPLS network34.

References: What is Label Edge Router (LER)? - Definition from Techopedia, LER - Label Edge Router - Mpirical

According to RFC1918, there are three network blocks reserved as private networks that are not allocated to any specific organization and are not routable on the public Internet. These are:

• 10.0.0.0/8 (10.0.0.0 - 10.255.255.255)
• 172.16.0.0/12 (172.16.0.0 - 172.31.255.255)
• 192.168.0.0/16 (192.168.0.0 - 192.168.255.255)

Out of these, only option B (10.254.1.0/24) falls within one of the private network blocks (10.0.0.0/8). Option A (172.16.1.0/9) is not valid because it exceeds the /12 prefix length of the private network block (172.16.0.0/12). Option C (193.168.1.0/24) is not valid because it does not belong to any of the private network blocks, and is actually assigned to RIPE NCC as a public network block . Option D (172.15.1.0/24) is also not valid because it does not belong to any of the private network blocks, and is actually assigned to ARIN as a public network block . References: RFC 1918: Address Allocation for Private Internets, Private network - Wikipedia, [RIPE NCC IPv4 Address Space Chart], [ARIN WHOIS Database Search]

LDP relies on IGP for all routing-related decisions. LDP is a protocol that distributes labels in an MPLS environment, but it does not perform any routing functions. LDP uses the underlying routing information provided by an IGP, such as OSPF or IS-IS, to forward label packets. LDP and IGP do not exchange their databases at regular intervals, but rather use hello messages to maintain adjacencies and sessions. References: Ericsson IP Networking - Routing Protocols, Label Distribution Protocol - Wikipedia