Editing Border Gateway Protocol (section)

== Implementations ==
Routers, especially small ones intended for [[small office/home office]] (SOHO) use, may not include BGP capability. Other commercial routers may need a specific software executable image that supports BGP, or a license that enables it. Devices marketed as [[layer-3 switch]]es are less likely to support BGP than devices marketed as [[Router (computing)|routers]], but many high-end layer-3 switches can run BGP.

Products marketed as switches may have a size limitation on BGP tables that is far smaller than a full Internet table plus internal routes. These devices may be perfectly reasonable and useful when used for BGP routing of some smaller part of the network, such as a [[confederation-AS]] representing one of several smaller enterprises that are linked, by a BGP [[backbone of backbones]], or a small enterprise that announces routes to an ISP but only accepts a [[default route]] and perhaps a small number of aggregated routes.

A BGP router used only for a network with a single point of entry to the Internet may have a much smaller routing table size (and hence RAM and CPU requirement) than a multihomed network. Even simple multihoming can have modest routing table size. The actual amount of memory required in a BGP router depends on the amount of BGP information exchanged with other BGP speakers and the way in which the particular router stores BGP information. The router may have to keep more than one copy of a route, so it can manage different policies for route advertising and acceptance to a specific neighboring AS. The term ''view'' is often used for these different policy relationships on a running router.

If one router implementation takes more memory per route than another implementation, this may be a legitimate design choice, trading processing speed against memory. A full IPv4 BGP table {{as of|August 2015|lc=on}} is in excess of 590,000 prefixes.<ref name="Potaroo&nbsp;— BGP Table data"/> Large ISPs may add another 50% for internal and customer routes. Again depending on implementation, separate tables may be kept for each view of a different peer AS.

Notable free and open-source implementations of BGP include:
* [[Bird Internet routing daemon|BIRD]], a [[GPL]] routing package for Unix-like systems.
* [[FRRouting]], a fork of Quagga for [[Unix-like]] systems; and its ancestors:
** [[Quagga (software)|Quagga]], a fork of GNU Zebra for [[Unix-like]] systems (no longer developed).
** [[GNU Zebra]], a GPL routing suite supporting BGP4 (decommissioned).<ref>{{Cite web|url=https://www.gnu.org/software/zebra/|title=Zebra - GNU Project - Free Software Foundation}}</ref>
* [[OpenBGPD]], a [[BSD licence|BSD-licensed]] implementation by the [[OpenBSD]] team.
* [[XORP]], the eXtensible Open Router Platform, a BSD-licensed suite of routing protocols.

Systems for testing BGP conformance, load or stress performance come from vendors such as:
* [[Agilent Technologies]]
* [[GNS3]] open source [[network simulator]]
* [[Ixia (company)|Ixia]]
* [[Spirent]]