5.8.2. BGP

BGP (Border Gateway Protocol) is a dynamic routing protocol which relates to exterior gateway protocols (EGP - External Gateway Protocol). Presently, it is the key dynamic routing protocol on the Internet. BGP is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS), i.e. groups of routers under the unified technical and administrative control. BGP uses intra-domain routing protocols for identification of internal routes and cross-domain routing protocols for identification of routes to deliver packets to other ASes. The delivered information may include a list of ASes that are accessible through a given system. The best routes are selected according to the network-specific rules. For more details on BGP, please refer to the corresponding technical documentation.

To set up BGP in UserGate, perform the following steps:

Name

Description

Step 1. Enable a BGP router.

In the UserGate console, go to Network-->BGP--> BGP router, click Settings and configure parameters of the BGP router.

Step 2. Add at least one BGP peer.

In the UserGate console, go to Network-->BGP-->BGP peers, click Add and configure parameters of the router included in the peer AS. Add as many peers as necessary.

Step 3. Optional. Set up the filters and Routemap in order to limit the number of incoming routes.

In the UserGate console, go to Network-->BGP-->Routemaps or Network-->BGP--> Filters, click Add and configure parameters of the Routemap/filters. Add as many Routemap/filters as necessary for proper operation of BGP in your organization.

When setting up a BGP router, make sure to provide the following parameters:

Name

Description

Enabled

Enables or disables a given BGP router.

Router ID

IP address of the router. Must be the same as one of IP addresses assigned to network interfaces of UserGate.

ID of the autonomous system (AS).

An autonomous system is a system of IP networks and routers managed by one or more providers with the unified routing policy. ID of an autonomous system indicates routers that belong to a given system.

Redistribute

Notifies other BGP routers about routes directly connected to a UserGate-network (connected), routes added by the administrator in the Routes section (kernel), or routes obtained through BGP.

Multiple path

Enables traffic balancing to routes with the same cost.

Networks

A list of networks in a given AS.

To add BGP peers, click Add and provide the following parameters:

Name

Description

Enabled

Enables or disables a given peer

Interface

One of the existing system interfaces through which a given peer should be accessible

Host

IP address of a peer

Description

An arbitrary description of a peer

Remote ASN

ID of an autonomous system which a peer relates to

Weight

The weight of given routes obtained from a given peer

TTL

The maximum number of hops allowed in the route to a given peer

Announce next-hop-self for BGP

Replace the next-hop-self value with own IP address when a given peer is BGP

Multihop for eBPGP

Indicates that a connection to a given peer is indirect (several hops)

Route reflector client

Indicates whether a given peer is a Route reflector client

Soft reconfiguration

Use soft reconfiguration (without disconnections) for configuration updates

Default originate

Announce the default route to a given peer

Authentication

Enables authentication for a given peer and sets a password for authentication

Filters for BGP peers

Restricts access to information about routes obtained from peers or announced routes to them

Routemaps

Routemaps are used for managing route tables and defining conditions upon which routes must be redistributed among domains

Routemaps help filtering routes during redistribution and changing various route attributes. Provide the following parameters when creating a new routemap:

Name

Description

Name

Name of a given routemap

Operation

Sets an action for a given routemap. Possible values:

  • Allow - allows a flow of traffic matching the routemap's conditions.

  • Block - prohibits a flow of traffic matching the routemap's conditions.

Compare by

Conditions for applying a routemap. Possible values:

  • IP. When this condition is selected, then add all IP addresses required for this condition on the IP address tab.

  • AS path. When this condition is selected, then add all IDs of the autonomous networks required for this condition on the AS path tab. It is allowed to use regular expressions in POSIX 1003.2 or additional underscore (_) that is interpreted as follows:
    - space
    - comma
    - string start
    - string end
    - AS set delimiter { and }
    - AS confederation delimiter ( and )

  • Community. When this condition is selected, then add all strings of BGP communities required for this condition on the Community tab.

Set next hop

Sets the next hop value to the indicated IP address for the filtered routes

Set weight

Sets a preference to the indicated value for the filtered routes

Set metric

Sets a metric to the indicated value for the filtered routes

Set preference

Sets a preference to the indicated value for the filtered routes

Set AS-prepend

Sets AS-prepend, i.e. a list of autonomous systems to be added for a given route

Community

Sets a BGP community for the filtered routes

The filter allows sorting out various routes during redistribution. Provide the following parameters when creating a new filter:

Name

Description

Name

Name of a given filter

Action

Sets an action for a given filter. Possible values:

  • Allow - allows a flow of traffic matching the filter's conditions.

  • Block - prohibits a flow of traffic matching the filter's conditions.

Filter by

Conditions for applying a filter. Possible values:

  • IP. When this condition is selected, then add all IP addresses required for this condition on the IP addresses tab.

  • AS path. When this condition is selected, then add all IDs of the autonomous networks required for this condition on the AS path tab.