Users Guide

TX: 200ms, RX: 200ms, Multiplier: 49
Role: active
VRF: default
Client Registered: bgp
Uptime: 01:58:09
Statistics:
Number of packets received from neighbor: 7138
Number of packets sent to neighbor: 7138
Supported
releases
10.4.1.0 or later
Border Gateway Protocol
Border Gateway Protocol (BGP) is an interautonomous system routing protocol that transmits interdomain routing information
within and between autonomous systems (AS). BGP exchanges 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). AS numbers 64512
through 65534 are reserved for private purposes. 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
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.
Stub AS Connected to only one AS.
Transit 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.
Classless interdomain routing
BGPv4 supports classless interdomain routing (CIDR) with aggregate routes and AS paths. CIDR defines a network using a
prefix consisting of an IP address and mask, resulting in efficient use of the IPv4 address space. Using aggregate routes reduces
the size of routing tables.
Path-vector routing
570
Layer 3