Dynamic routing protocols are used to signal which networks are currently connected to each of the routers. Routers communicate using routing protocols. UserGate updates the kernel routing table in accordance with the information it receives from the neighboring routers. Dynamic routing does not change how the kernel performs routing at the IP layer. The kernel keeps looking up routes to hosts and networks as well as default routes in its routing table. The only thing that changes is how routes are managed in the routing table: instead of the manual method, they are added and removed dynamically. Routes are only added to the virtual router in which the BGP protocol is configured.
BGP (Border Gateway Protocol) is a dynamic routing protocol classified as an External Gateway Protocol (EGP). Currently, it is the main dynamic routing protocol used on the Internet. The BGP protocol is designed to exchange routing and reachability information among autonomous systems (AS), which are groups of routers with common technical management and administration that use intra-domain routing protocols to determine routes within a group and an inter-domain routing protocol to determine routes for packet delivery to other ASs. The information transmitted includes the list of ASs that can be accessed via this system. The best routes are selected based on the rules that are in place in the network. For more details on how the BGP protocol works, see the relevant technical documentation.
To configure BGP in UserGate, follow these steps:
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Task |
Description |
|---|---|
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Step 1. Select a virtual router. |
If there are several virtual routers, select the desired one. |
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Step 2. Enable the BGP router. |
In the UserGate console, go to the Network --> Virtual routers section, select BGP in the menu, and configure the BGP router. |
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Step 3. Specify the filters and optional routemaps to limit the number of routes to receive. |
In the Filters section, click Add and configure the Routemap and filter settings. Add as many routemaps/filters as required for BGP to work in your organization. |
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Step 4. Add at least one BGP neighbor (peer). |
In the Neighbors section, click Add and configure the router settings for the neighboring AS. Add as many neighbors as required. Important! RFC 8212 includes a mandatory requirement that export and import filters be added for each neighbor. Without import filters, the router will not receive routes from that neighbor, and without export filters, the router will not advertise routes to that neighbor. If several IP addresses are assigned to the UserGate interface from which a connection is established to a neighbor, then when configuring a BGP neighbor, if there is no NAT rule that enforces the source address for a BGP session with this neighbor, you must specify the main one as the UserGate address (primary) IP address, i.e. the address that is first in the list in the interface settings. |
To configure a BGP router, provide the following settings:
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Name |
Description |
|---|---|
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Enabled |
Enables or disables this BGP router. |
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Router ID |
The router's IP address. Must match one of the IP addresses assigned to the UserGate network interfaces that belong to this virtual router. |
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AS number |
An autonomous system is a system of IP networks and routers managed by one or more operators that have a single routing policy. The autonomous system number identifies the router as belonging to that system. |
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Redistribute |
Enables the routes towards networks directly connected to UserGate, static routes added by the administrator for this virtual router (kernel), or routes received using the OSPF protocol to be distributed to other BGP routers. |
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Multiple path |
Enables traffic load balancing to routes with identical cost. |
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Networks |
The list of networks that belong to this AS. |
To add BGP neighbors, click Add and provide these settings:
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Name |
Description |
|---|---|
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Enabled |
Enables or disables this neighbor. |
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Host |
The neighbor's IP address. |
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Description |
An arbitrary description for the neighbor. |
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Remote ASN |
The neighbor's AS number. |
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Weight |
The weight assigned to route data received from this neighbor. |
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TTL |
The maximum allowed number of hops to this neighbor. |
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Announce self as next hop for BGP |
Replace the next-hop-self value with own IP address, if the neighbor uses BGP. |
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Multihop for eBGP |
Indicates that the connection to this neighbor is indirect (more than a single hop). |
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Route reflector client |
Indicates if the neighbor is a route reflector client. |
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Soft reconfiguration |
Use soft reconfiguration (without terminating connections) for configuration updates. |
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Default originate |
Advertise the default route to this neighbor. |
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Authentication |
Enables authentication for this neighbor. The authentication password is set here. |
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BGP neighbor filters |
Limits the route information received from the neighbors or advertised to them. |
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Routemaps |
Routemaps are used to manage routing tables and specify the match conditions under which routes are passed between domains. |
A routemap allows filtering of routes on redistribution and modification of various route attributes. To create a routemap, provide the following settings:
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Name |
Description |
|---|---|
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Name |
The routemap name. |
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Action |
Sets the action for this routemap. Can take the following values:
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Match by |
Routemap conditions. Can take the following values:
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Set next hop |
Set the next hop value for the filtered routes to this IP address. |
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Set weight |
Set the weight for the filtered routes to this value. |
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Set metric |
Set the metric for the filtered routes to this value. |
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Set preference |
Set the preference for the filtered routes to this value. |
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Set AS prepend |
Set the AS-prepend value, which is a list of autonomous systems added for this route. |
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Community |
Set the BGP community value for the filtered routes. |
Filters allow you to filter routes when redistributing. To create a filter, provide the following settings:
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Name |
Description |
|---|---|
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Name |
The filter name. |
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Action |
Sets the action for this filter. Can take the following values:
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Filter by |
Filter conditions. Can take the following values:
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