Dell MX5108n OS10 Enterprise Edition User Guide for PowerEdge MX IO Modules Re - Page 272

6 Layer 3 Border Gateway Protocol (BGP) Provides an external gateway protocol that transmits inter-domain routing information within and between autonomous systems (see BGP Commands). Equal Cost MultiPath (ECMP) Provides next-hop packet forwarding to a single destination over multiple best paths (see ECMP Commands). IPv4 Routing Provides forwarding of packets to a destination IP address, based on a routing table. This routing table defines how packets are routed - dynamically, broadcasted directly to, using proxy ARP, as well as what type of information is included with the packets (see IPv4 Routing Commands). IPv6 Routing Provides routing for the IPv6 address space, stateless auto-configuration, header format simplifications, and improved support for options and extensions (see IPv6 Routing Commands). Open Shortest Path Provides a link-state routing protocol that communicates with all other devices in the same autonomous system First (OSPF) area using link-state advertisements (LSAs). OS10 supports up to 10,000 OSPF routes for OSPFv2 to designate up to 8,000 routes as external, and up to 2,000 as inter/intra area routes (see OSPF Commands). Virtual Router Redundancy Protocol (VRRP) Provides a mechanism to eliminate a single point of failure in a statically routed network (see VRRP Commands). Border gateway protocol Border gateway protocol (BGP) is an interautonomous system routing protocol that transmits interdomain routing information within and between autonomous systems (AS). The primary function of BGP is to exchange network reachability information with other BGP systems. BGP adds reliability to network connections by using multiple paths from one router to another. Unlike most routing protocols, BGP uses TCP as its transport protocol. Autonomous systems BGP autonomous systems are a collection of nodes under a single administration with shared network routing policies. Each AS has a number, which an Internet authority assigns-you do not assign the BGP number. The Internet Assigned Numbers Authority (IANA) identifies each network with a unique AS number (ASN). The AS numbers 64512 through 65534 are reserved for private purposes. The AS numbers 0 and 65535 cannot be used in a live environment. IANA assigns valid AS numbers in the range of 1 to 64511. Multihomed AS Stub AS Transit AS Maintains connections to more than one other AS. This group allows the AS to remain connected to the Internet if a complete failure occurs to one of their connections. This type of AS does not allow traffic from one AS to pass through on its way to another AS. Connected to only one AS. Provides connections through itself to separate networks. For example, Router 1 uses Router 2-the transit AS, to connect to Router 4. Internet service providers (ISPs) are always a transit AS because they provide connections from one network to another. An ISP uses a transit AS to sell transit service to a customer network. When BGP operates inside an AS - AS1 or AS2, it functions as an internal border gateway protocol (IBGP). When BGP operates between AS endpoints - AS1 and AS2, it functions as an external border gateway protocol (EBGP). IBGP provides routers inside the AS with the path to reach a router external to the AS. EBGP routers exchange information with other EBGP routers and IBGP routers to maintain connectivity and accessibility. 272 Layer 3