Document toolboxDocument toolbox

Configuring BGP Settings

Owned by Shirly Tsang
Last updated: Sept 06, 2024 by Sri Raghu
8 min read

Use the Routing Protocol step of the Create BGP Protocol Settings wizard to configure the BGP settings and set up a service instance. Specify the following:

BGPD Enabled: Use the toggle switch to enable or disable the BGP service.

IPv4 Prefix List

When you configure an IPv4 prefix list, you filter BGP routes by assigning the prefix list to a neighbor rather than by using an autonomous system (AS) path filter. The process for evaluating a prefix against a prefix list ends when a match is found. For example, to disallow redistribution of a route for 10.0.0.0/24 through BGP, define an IPv4 prefix list that includes this prefix; the system will reference it from the BGP redistribution route map.

To create an IPv4 prefix list, click Add and specify the following:

  • Name: Enter the name of the prefix list. Create a name that does not exceed 64 characters. Use numbers, any special characters, uppercase and lowercase letters, and even spaces. Start and end a name with any character other than a space. Leading and trailing spaces will be trimmed off automatically.

  • Description: Enter the description for the IPv4 prefix list.

  • IPv4 Prefix List: Click Add and specify the following:

    • ACTION: Choose the action you want to apply to this IPv4 prefix list. You can either allow or deny traffic to the route that matches the prefix list.

    • PREFIX: Enter the IPv4 prefix. For example, if you want to permit or deny traffic to 10.0.0.0/8, enter 10.0.0.0/8 here.

    • PREFIX LENGTH GE: This item specifies the prefix length that is greater than or equal to the subnet’s value. This is the lowest value of the range of prefix lengths.

    • IPV4 PREFIX LENGTH LE: This item specifies the prefix length that is less than or equal to the subnet’s value. This is the highest value of the range of prefix lengths.

    • SEQUENCE: To specify the entry point of this IPv4 prefix list among other BGP configurations, enter a number from 1 to 2147483646. For example, if you configure ACTION = Permit, IPv4 PREFIX = 10.0.0.0/8, and IPv4 PREFIX LENGTH LESS OR EQUAL = 19, then all networks that fall within the 10.0.0.0/8 range AND have a subnet mask of /19 or less will be allowed through BGP.

To add the prefix list, click Add.

Route Map

A route map evaluates the matching conditions until a successful match occurs. After the match occurs, the route map stops evaluating the matching conditions and starts executing the conditions in the order in which they were configured. If a successful match does not occur, the route map “falls through” and evaluates the next sequence number until all configured route map entries have been evaluated or a successful match has occurred. To identify an entry, each route map sequence is tagged with a sequence number. Route map entries are evaluated from the lowest sequence number to the highest sequence number. 

To create a route map, click Add and specify the following:

  • Name: Enter the name of the route map.

  • Action: The action configured for the route map rule. This can be DENY or PERMIT.

  • Description: Enter the description for the route map.

  • Sequence: The route map sequence indicates the position of a new route map in the list of route maps already configured using the same name. The range of the sequence number is from 1 to 10.

  • Match Conditions: Click Add and specify the following in the table:

    • Condition: From the drop-down list, choose the condition to be matched.

    • Condition Value: From the drop-down list, choose the value to be matched.

  • Set Community: This sets the BGP community for a route matched by the route map. Click Add and specify the following in the table:

    • Community: Enter the community number to use. This is either a number from 1 to 4,294,967,200 or the predefined communities of no-export or no-advertise.

    • Description: Enter the description for this community.

To save the configuration, click Add.

BGPD Config

Expand the Address Family IPv4 Unicast section, and specify the following:

  • Admin Distance: An administrative distance or route preference is a rating of trustworthiness of a source of routing information. It is the first criterion that a router uses to determine the routing protocol to be used if two protocols provide the route information for the same destination. An administrative distance has only local significance and is not advertised in routing-related updates.

  • External: Enter the rating for routes learned from EBGP (External Border Gateway Protocol). The smaller the number, the more trustworthy the protocol. EBGP routes received from an EBGP peer can be advertised to EBGP and IBGP peers. 

  • Internal: Enter the rating for routes learned from IBGP (Internal Border Gateway Protocol). The smaller the number, the more trustworthy the protocol. IBGP routes received from an IBGP peer cannot be advertised to another IBGP peer but can be advertised to an EBGP peer. 

  • Local: Enter the local IP address.

  • Aggregate Route: Aggregate specific routes into one route. This enables you to hide a number of prefixes from being advertised to neighbors. Click Add and use IP ADDRESSES to add the router into which you want other routes to aggregate. To delete an aggregate route, select it and click Remove. 

  • Maximum Paths: Configure the following settings to determine whether and when a router will add multiple EBGP or IBGP routes to the IP-routing table.

    • EBGP: Enter the number of possible IP routes learned from EBGP.

    • IBGP: Enter the number of possible IP routes learned from IBGP.

    • Network Config: To add an IPv4 or IPv6 network configuration, click Add and enter the IP address in IP ADDRESSES. To delete a network configuration, select an IP address and click Remove.

Expand the Global section and specify the following:

  • Fast External Failover: If the route used to reach the peer is invalid or goes offline, set this toggle switch to True; this will terminate external BGP sessions of any directly adjacent peer without waiting for the hold-down timer to expire. To disable fast external failover, switch the toggle to False.

  • Graceful Restart: To announce a graceful restart, set this toggle switch to True. If you set it to False, the graceful restart will not be announced. 

  • Graceful Shutdown: To announce a graceful shutdown, set this toggle switch to True. If you set it to False, the graceful restart will not be announced.

  • Local As: Enter the number of the AS here. When you enter the number, the system will permit a router to appear to be a member of the second AS in addition to being a member of the actual AS.

  • Log Neighbor Changes: To log changes from a BGP neighbor, set this toggle switch to True.

  • Router Id: Enter the router ID, which is a 4-byte field that is set to the highest IP address on the router. It is used in the BGP algorithm to determine the best path to a destination, and the preference is for the BGP router with the lowest router ID. By using a configured hold time and KEEPALIVE messages, the BGP mechanism ensures the BGP neighbors are still alive.

Configure the following global BGP timers:

o    Hold Time: Enter the number of seconds that a router will wait for incoming BGP messages before it assumes a neighbor is dead. This heartbeat mechanism ensures that BGP neighbors are healthy and alive. The hold time you enter here sets the hold timer for each BGP neighbor. Upon receipt of an UPDATE or a KEEPALIVE message, the hold timer resets to the initial value. If the hold timer reaches zero, the BGP session will be terminated, the routing paths from that neighbor will be removed, and, for the prefixes affected, an appropriate message about withdrawal of an update route will be sent to other BGP neighbors. 

o    Keep Alive: Enter the number of seconds for the time interval during which a router will send KEEPALIVE messages to BGP neighbors to keep the BGP session alive. Typically, the keepalive timer is one-third of the hold time.

o    Update Delay: Enter the number of seconds for the minimum delay between updates for a neighbor session.

For BGP to run in your network, you must configure at least one peer group that includes at least one neighbor. First, determine which neighbors are internal and which are external to your local AS. Expand the Neighbors section, click Add, and specify the following to set your BGP neighbors:

  • Peer Group Name: Enter the BGP peer group’s name.

  • Remote Address: Specify the remote IP address you want to use for your BGP peer group.

Expand the Neighbor Param drop-down section, and specify the following:

  • Description: Enter the description for the BGP peer group.

  • Graceful Restart: Set this toggle switch to True to enable and False to disable the graceful restart for a BGP neighbor.

  • Remote Access: Enter the remote IP address for the BGP peer group.

  • Password: Enter the password used to reach the BGP neighbor.

  • Remote As: Specify the IP address of the remote AS.

  • TTL Security: Enter a minimum TTL (Time To Live) value for incoming IP packets received from peers in the remote AS. 

  • Update Source: For BGP connections to the neighbor to get sourced from the loopback IP specify the IP address of the loopback interface.

Expand the Admin Shutdown section, and specify the following: 

  • Enable: Set this toggle switch to True to enable administrative shutdown. The BGP peer groups will be shut down administratively, and the configuration will not be removed from BGP.

  • Next Hop Self: Set this toggle switch to True. This will enable the net hop network address you want to add to the routing table and will ensure that the network is reachable.

  • Soft Reconfiguration: Set this toggle switch to True to generate inbound updates from a BGP neighbor and to change and activate BGP policies without clearing the BGP session. 

  • Weight Attribute: Enter a number for the weight that BGP will use to choose a path. Note that the path with the highest weight is preferred.

Expand the Timers section, and specify the following:

  • Advertise Interval: Enter the number of seconds that must elapse between an advertisement or a withdrawal of routes from a BGP peer.

  • Connect Time: Specify the length of time, in seconds, during which the BGP peer is to stay connected.

  • Hold Time: Specify the number of seconds that may elapse between successive KEEPALIVE or UPDATE messages received from a BGP peer before the peer connection ends.

  • Keep Alive: Specify the length of time, in seconds, during which routes from a BGP peer are to be suppressed according to the setting for the hold time.

To save the configuration, click Add.

Expand Peer Groups, and do the following:

Click Add and enter the PEER GROUP NAME. 

Expand the Neighbor Param section, and specify the following:

  • Description: Enter the description for the BGP peer group.

  • Graceful Restart: Set this toggle switch to True to enable and False to disable a graceful restart for a BGP neighbor.

  • Password: Enter the password used to reach the BGP neighbor.

  • Remote As: Specify the IP address of the remote AS.

  • TTL Security: Enter a minimum TTL (Time To Live) value for incoming IP packets received from peers in the remote AS. 

  • Update Source: For BGP connections to the neighbor to get sourced from the loopback IP, specify the IP address of the loopback interface.

Expand the Admin Shutdown section, and specify the following:

  • Enable: To enable administrative shutdown, set this toggle switch to True. The BGP peer groups will be shut down administratively, and the configuration will not be removed from BGP.

  • Message: Enter the message you want to be used when the BGP peer groups are shut down.

Expand the Neighbor IPv4 Unicast section, and specify the following:

  • Enabled: To enable neighbor IPv4 unicast, set this toggle switch to True.

  • Next Hop Self: Enter the net hop network address you want to add to the routing table to ensure that the network is reachable.

  • Soft Reconfiguration: Set this toggle switch to True to generate inbound updates from a BGP neighbor and to change and activate BGP policies without clearing the BGP session. 

  • Weight Attribute: Enter a number for the weight that BGP will use to choose a path. Note that the path with the highest weight is preferred.

Expand the Timers section, and specify the following:

  • Advertise Interval: Enter the number of seconds that must elapse between an advertisement or a withdrawal of routes from a BGP peer.

  • Connect Time: Specify the length of time, in seconds, during which the BGP peer is to stay connected.

  • Hold Time: Specify the number of seconds that may elapse between successive KEEPALIVE or UPDATE messages received from a BGP peer before the peer connection ends.

  • Keep Alive: Specify the length of time, in seconds, during which routes from a BGP peer are to be suppressed according to the setting for the hold time.

To save the configuration, click Add.

Click Next to view the Service Configuration Summary.