BGP
BGP is one of the Exterior Gateway Protocols and the de facto standard interdomain routing protocol. The latest BGP version is 4. BGP-4 is described in RFC 1771 and updated by RFC 4271. RFC 2858 adds multiprotocol support to BGP.
VyOS makes use of FRR and we would like to thank them for their effort!
Basic Concepts
Autonomous Systems
From RFC 1930:
An AS is a connected group of one or more IP prefixes run by one or more network operators which has a SINGLE and CLEARLY DEFINED routing policy.
Each AS has an identifying number associated with it called an ASN. This is a two octet value ranging in value from 1 to 65535. The AS numbers 64512 through 65535 are defined as private AS numbers. Private AS numbers must not be advertised on the global Internet. The 2-byte AS number range has been exhausted. 4-byte AS numbers are specified in RFC 6793, and provide a pool of 4294967296 AS numbers.
The ASN is one of the essential elements of BGP. BGP is a distance vector routing protocol, and the AS-Path framework provides distance vector metric and loop detection to BGP.
Address Families
Multiprotocol extensions enable BGP to carry routing information for multiple network layer protocols. BGP supports an Address Family Identifier (AFI) for IPv4 and IPv6.
Route Selection
The route selection process used by FRR’s BGP implementation uses the following decision criterion, starting at the top of the list and going towards the bottom until one of the factors can be used.
Weight check
Prefer higher local weight routes to lower routes.
Local preference check
Prefer higher local preference routes to lower.
Local route check
Prefer local routes (statics, aggregates, redistributed) to received routes.
AS path length check
Prefer shortest hop-count AS_PATHs.
Origin check
Prefer the lowest origin type route. That is, prefer IGP origin routes to EGP, to Incomplete routes.
MED check
Where routes with a MED were received from the same AS, prefer the route with the lowest MED.
External check
Prefer the route received from an external, eBGP peer over routes received from other types of peers.
IGP cost check
Prefer the route with the lower IGP cost.
Multi-path check
If multi-pathing is enabled, then check whether the routes not yet distinguished in preference may be considered equal. If
bgp bestpath as-path multipath-relaxis set, all such routes are considered equal, otherwise routes received via iBGP with identical AS_PATHs or routes received from eBGP neighbours in the same AS are considered equal.Already-selected external check
Where both routes were received from eBGP peers, then prefer the route which is already selected. Note that this check is not applied if
bgp bestpath compare-routeridis configured. This check can prevent some cases of oscillation.Router-ID check
Prefer the route with the lowest router-ID. If the route has an ORIGINATOR_ID attribute, through iBGP reflection, then that router ID is used, otherwise the router-ID of the peer the route was received from is used.
Cluster-List length check
The route with the shortest cluster-list length is used. The cluster-list reflects the iBGP reflection path the route has taken.
Peer address
Prefer the route received from the peer with the higher transport layer address, as a last-resort tie-breaker.
Capability Negotiation
When adding IPv6 routing information exchange feature to BGP. There were some proposals. IETF IDR adopted a proposal called Multiprotocol Extension for BGP. The specification is described in RFC 2283. The protocol does not define new protocols. It defines new attributes to existing BGP. When it is used exchanging IPv6 routing information it is called BGP-4+. When it is used for exchanging multicast routing information it is called MBGP.
bgpd supports Multiprotocol Extension for BGP. So if a remote peer supports the protocol, bgpd can exchange IPv6 and/or multicast routing information.
Traditional BGP did not have the feature to detect a remote peer’s capabilities, e.g. whether it can handle prefix types other than IPv4 unicast routes. This was a big problem using Multiprotocol Extension for BGP in an operational network. RFC 2842 adopted a feature called Capability Negotiation. bgpd use this Capability Negotiation to detect the remote peer’s capabilities. If a peer is only configured as an IPv4 unicast neighbor, bgpd does not send these Capability Negotiation packets (at least not unless other optional BGP features require capability negotiation).
By default, FRR will bring up peering with minimal common capability for the both sides. For example, if the local router has unicast and multicast capabilities and the remote router only has unicast capability the local router will establish the connection with unicast only capability. When there are no common capabilities, FRR sends Unsupported Capability error and then resets the connection.
Configuration
BGP Router Configuration
First of all you must configure BGP router with the ASN. The AS number is an identifier for the autonomous system. The BGP protocol uses the AS number for detecting whether the BGP connection is internal or external. VyOS does not have a special command to start the BGP process. The BGP process starts when the first neighbor is configured.
Set local autonomous system number that this router represents. This is a mandatory option!
Peers Configuration
Defining Peers
This command creates a new neighbor whose remote-as is <nasn>. The neighbor address can be an IPv4 address or an IPv6 address or an interface to use for the connection. The command is applicable for peer and peer group.
Create a peer as you would when you specify an ASN, except that if the
peers ASN is different than mine as specified under the protocols
bgp <asn> command the connection will be denied.
Create a peer as you would when you specify an ASN, except that if the
peers ASN is the same as mine as specified under the protocols
bgp <asn> command the connection will be denied.
BGP roles are defined in RFC RFC 9234 and provide an easy way to add route leak prevention, detection and mitigation. The local Role value is negotiated with the new BGP Role capability which has a built-in check of the corresponding value. In case of a mismatch the new OPEN Roles Mismatch Notification <2, 11> would be sent. The correct Role pairs are:
Provider - Customer
Peer - Peer
RS-Server - RS-Client
If strict is set the BGP session won’t become established
until the BGP neighbor sets local Role on its side. This
configuration parameter is defined in RFC RFC 9234 and is used to
enforce the corresponding configuration at your counter-parts side.
Routes that are sent from provider, rs-server, or the peer local-role (or if received by customer, rs-client, or the peer local-role) will be marked with a new Only to Customer (OTC) attribute.
Routes with this attribute can only be sent to your neighbor if your local-role is provider or rs-server. Routes with this attribute can be received only if your local-role is customer or rs-client.
In case of peer-peer relationship routes can be received only if OTC value is equal to your neighbor AS number.
All these rules with OTC will help to detect and mitigate route leaks and happen automatically if local-role is set.
This command disable the peer or peer group. To reenable the peer use the delete form of this command.
Set description of the peer or peer group.
Capability Negotiation
This command would allow the dynamic update of capabilities over an established BGP session.
Allow bgp to negotiate the extended-nexthop capability with it’s peer. If you are peering over a IPv6 Link-Local address then this capability is turned on automatically. If you are peering over a IPv6 Global Address then turning on this command will allow BGP to install IPv4 routes with IPv6 nexthops if you do not have IPv4 configured on interfaces.
Suppress sending Capability Negotiation as OPEN message optional parameter to the peer. This command only affects the peer is configured other than IPv4 unicast configuration.
When remote peer does not have capability negotiation feature, remote peer will not send any capabilities at all. In that case, bgp configures the peer with configured capabilities.
You may prefer locally configured capabilities more than the negotiated
capabilities even though remote peer sends capabilities. If the peer is
configured by override-capability, VyOS ignores received
capabilities then override negotiated capabilities with configured values.
Additionally you should keep in mind that this feature fundamentally disables the ability to use widely deployed BGP features. BGP unnumbered, hostname support, AS4, Addpath, Route Refresh, ORF, Dynamic Capabilities, and graceful restart.
This command allow override the result of Capability Negotiation with local configuration. Ignore remote peer’s capability value.
This command forces strictly compare remote capabilities and local capabilities. If capabilities are different, send Unsupported Capability error then reset connection.
You may want to disable sending Capability Negotiation OPEN message
optional parameter to the peer when remote peer does not implement
Capability Negotiation. Please use disable-capability-negotiation
command to disable the feature.
Peer Parameters
This command accept incoming routes with AS path containing AS number with the same value as the current system AS. This is used when you want to use the same AS number in your sites, but you can’t connect them directly.
The number parameter (1-10) configures the amount of accepted occurences of the system AS number in AS path.
This command is only allowed for eBGP peers. It is not applicable for peer groups.
This command override AS number of the originating router with the local AS number.
Usually this configuration is used in PEs (Provider Edge) to replace the incoming customer AS number so the connected CE ( Customer Edge) can use the same AS number as the other customer sites. This allows customers of the provider network to use the same AS number across their sites.
This command is only allowed for eBGP peers.
This command specifies attributes to be left unchanged for advertisements sent to a peer or peer group.
This command specifies a maximum number of prefixes we can receive from a given peer. If this number is exceeded, the BGP session will be destroyed. The number range is 1 to 4294967295.
This command forces the BGP speaker to report itself as the next hop for an advertised route it advertised to a neighbor.
This command removes the private ASN of routes that are advertised to the configured peer. It removes only private ASNs on routes advertised to EBGP peers.
If the AS-Path for the route has only private ASNs, the private ASNs are removed.
If the AS-Path for the route has a private ASN between public ASNs, it is assumed that this is a design choice, and the private ASN is not removed.
Changes in BGP policies require the BGP session to be cleared. Clearing has a large negative impact on network operations. Soft reconfiguration enables you to generate inbound updates from a neighbor, change and activate BGP policies without clearing the BGP session.
This command specifies that route updates received from this neighbor will be stored unmodified, regardless of the inbound policy. When inbound soft reconfiguration is enabled, the stored updates are processed by the new policy configuration to create new inbound updates.
Note
Storage of route updates uses memory. If you enable soft reconfiguration inbound for multiple neighbors, the amount of memory used can become significant.
This command specifies a default weight value for the neighbor’s routes. The number range is 1 to 65535.
This command specifies the minimum route advertisement interval for the peer. The interval value is 0 to 600 seconds, with the default advertisement interval being 0.
This command allows peerings between directly connected eBGP peers using loopback addresses without adjusting the default TTL of 1.
This command specifies that the community attribute should not be sent in route updates to a peer. By default community attribute is sent.
This command allows sessions to be established with eBGP neighbors
when they are multiple hops away. When the neighbor is not directly
connected and this knob is not enabled, the session will not establish.
The number of hops range is 1 to 255. This command is mutually
exclusive with ttl-security hops.
Specify an alternate AS for this BGP process when interacting with the specified peer or peer group. With no modifiers, the specified local-as is prepended to the received AS_PATH when receiving routing updates from the peer, and prepended to the outgoing AS_PATH (after the process local AS) when transmitting local routes to the peer.
If the no-prepend attribute is specified, then the supplied
local-as is not prepended to the received AS_PATH.
If the replace-as attribute is specified, then only the supplied
local-as is prepended to the AS_PATH when transmitting local-route
updates to this peer.
Note
This command is only allowed for eBGP peers.
Configures the BGP speaker so that it only accepts inbound connections from, but does not initiate outbound connections to the peer or peer group.
This command specifies a MD5 password to be used with the tcp socket that is being used to connect to the remote peer.
This command enforces Generalized TTL Security Mechanism (GTSM),
as specified in RFC 5082. With this command, only neighbors
that are specified number of hops away will be allowed to
become neighbors. The number of hops range is 1 to 254. This
command is mutually exclusive with ebgp-multihop.
Peer Groups
Peer groups are used to help improve scaling by generating the same update information to all members of a peer group. Note that this means that the routes generated by a member of a peer group will be sent back to that originating peer with the originator identifier attribute set to indicated the originating peer. All peers not associated with a specific peer group are treated as belonging to a default peer group, and will share updates.
This command defines a new peer group. You can specify to the group the same parameters that you can specify for specific neighbors.
Note
If you apply a parameter to an individual neighbor IP address, you override the action defined for a peer group that includes that IP address.
Network Advertisement Configuration
This command is used for advertising IPv4 or IPv6 networks.
Note
By default, the BGP prefix is advertised even if it’s not present in the routing table. This behaviour differs from the implementation of some vendors.
This configuration modifies the behavior of the network statement. If you have this configured the underlying network must exist in the routing table.
By default, VyOS does not advertise a default route (0.0.0.0/0) even if it is
in routing table. When you want to announce default routes to the peer, use
this command. Using optional argument route-map you can inject the
default route to given neighbor only if the conditions in the route map are
met.
Route Aggregation Configuration
This command specifies an aggregate address. The router will also announce longer-prefixes inside of the aggregate address.
This command specifies an aggregate address with a mathematical set of autonomous systems. This command summarizes the AS_PATH attributes of all the individual routes.
Redistribution Configuration
This command redistributes routing information from the given route source to the BGP process. There are six modes available for route source: connected, kernel, ospf, rip, static, table.
General Configuration
Common parameters
This command specifies the router-ID. If router ID is not specified it will use the highest interface IP address.
This command defines the maximum number of parallel routes that the BGP can support. In order for BGP to use the second path, the following attributes have to match: Weight, Local Preference, AS Path (both AS number and AS path length), Origin code, MED, IGP metric. Also, the next hop address for each path must be different.
This command enable logging neighbor up/down changes and reset reason.
This command disables route reflection between route reflector clients.
By default, the clients of a route reflector are not required to be
fully meshed and the routes from a client are reflected to other clients.
However, if the clients are fully meshed, route reflection is not required.
In this case, use the no-client-to-client-reflection command
to disable client-to-client reflection.
Disable immediate session reset if peer’s connected link goes down.
This command is useful if one desires to loosen the requirement for BGP to have strictly defined neighbors. Specifically what is allowed is for the local router to listen to a range of IPv4 or IPv6 addresses defined by a prefix and to accept BGP open messages. When a TCP connection (and subsequently a BGP open message) from within this range tries to connect the local router then the local router will respond and connect with the parameters that are defined within the peer group. One must define a peer-group for each range that is listed. If no peer-group is defined then an error will keep you from committing the configuration.
This command goes hand in hand with the listen range command to limit the amount of BGP neighbors that are allowed to connect to the local router. The limit range is 1 to 5000.
This command changes the eBGP behavior of FRR. By default FRR enables RFC 8212 functionality which affects how eBGP routes are advertised, namely no routes are advertised across eBGP sessions without some sort of egress route-map/policy in place. In VyOS however we have this RFC functionality disabled by default so that we can preserve backwards compatibility with older versions of VyOS. With this option one can enable RFC 8212 functionality to operate.
Administrative Distance
This command change distance value of BGP. The arguments are the distance values for external routes, internal routes and local routes respectively. The distance range is 1 to 255.
Timers
This command specifies hold-time in seconds. The timer range is 4 to 65535. The default value is 180 second. If you set value to 0 VyOS will not hold routes.
Route Dampening
When a route fails, a routing update is sent to withdraw the route from the network’s routing tables. When the route is re-enabled, the change in availability is also advertised. A route that continually fails and returns requires a great deal of network traffic to update the network about the route’s status.
Route dampening wich described in RFC 2439 enables you to identify routes that repeatedly fail and return. If route dampening is enabled, an unstable route accumulates penalties each time the route fails and returns. If the accumulated penalties exceed a threshold, the route is no longer advertised. This is route suppression. Routes that have been suppressed are re-entered into the routing table only when the amount of their penalty falls below a threshold.
A penalty of 1000 is assessed each time the route fails. When the penalties reach a predefined threshold (suppress-value), the router stops advertising the route.
Once a route is assessed a penalty, the penalty is decreased by half each time a predefined amount of time elapses (half-life-time). When the accumulated penalties fall below a predefined threshold (reuse-value), the route is unsuppressed and added back into the BGP routing table.
No route is suppressed indefinitely. Maximum-suppress-time defines the maximum time a route can be suppressed before it is re-advertised.
This command defines the amount of time in minutes after which a penalty is reduced by half. The timer range is 10 to 45 minutes.
This command defines the accumulated penalty amount at which the route is re-advertised. The penalty range is 1 to 20000.
This command defines the accumulated penalty amount at which the route is suppressed. The penalty range is 1 to 20000.
Route Selection Configuration
This command provides to compare the MED on routes, even when they were received from different neighbouring ASes. Setting this option makes the order of preference of routes more defined, and should eliminate MED induced oscillations.
This command specifies that the length of confederation path sets and sequences should be taken into account during the BGP best path decision process.
This command specifies that BGP decision process should consider paths of equal AS_PATH length candidates for multipath computation. Without the knob, the entire AS_PATH must match for multipath computation.
Ensure that when comparing routes where both are equal on most metrics, including local-pref, AS_PATH length, IGP cost, MED, that the tie is broken based on router-ID.
If this option is enabled, then the already-selected check, where already selected eBGP routes are preferred, is skipped.
If a route has an ORIGINATOR_ID attribute because it has been reflected, that ORIGINATOR_ID will be used. Otherwise, the router-ID of the peer the route was received from will be used.
The advantage of this is that the route-selection (at this point) will be more deterministic. The disadvantage is that a few or even one lowest-ID router may attract all traffic to otherwise-equal paths because of this check. It may increase the possibility of MED or IGP oscillation, unless other measures were taken to avoid these. The exact behaviour will be sensitive to the iBGP and reflection topology.
This command specifies that BGP considers the MED when comparing routes originated from different sub-ASs within the confederation to which this BGP speaker belongs. The default state, where the MED attribute is not considered.
This command specifies that a route with a MED is always considered to be better than a route without a MED by causing the missing MED attribute to have a value of infinity. The default state, where the missing MED attribute is considered to have a value of zero.
This command specifies the default local preference value. The local preference range is 0 to 4294967295.
This command provides to compare different MED values that advertised by neighbours in the same AS for routes selection. When this command is enabled, routes from the same autonomous system are grouped together, and the best entries of each group are compared.
Route Filtering Configuration
In order to control and modify routing information that is exchanged between peers you can use route-map, filter-list, prefix-list, distribute-list.
For inbound updates the order of preference is:
route-map
filter-list
prefix-list, distribute-list
For outbound updates the order of preference is:
prefix-list, distribute-list
filter-list
route-map
Note
The attributes
prefix-listanddistribute-listare mutually exclusive, and only one command (distribute-list or prefix-list) can be applied to each inbound or outbound direction for a particular neighbor.
This command applies the access list filters named in <number> to the
specified BGP neighbor to restrict the routing information that BGP learns
and/or advertises. The arguments export and import
specify the direction in which the access list are applied.
This command applies the prfefix list filters named in <name> to the
specified BGP neighbor to restrict the routing information that BGP learns
and/or advertises. The arguments export and import
specify the direction in which the prefix list are applied.
This command applies the route map named in <name> to the specified BGP
neighbor to control and modify routing information that is exchanged
between peers. The arguments export and import
specify the direction in which the route map are applied.
This command applies the AS path access list filters named in <name> to the
specified BGP neighbor to restrict the routing information that BGP learns
and/or advertises. The arguments export and import
specify the direction in which the AS path access list are applied.
This command enables the ORF capability (described in RFC 5291) on the
local router, and enables ORF capability advertisement to the specified BGP
peer. The receive keyword configures a router to advertise ORF
receive capabilities. The send keyword configures a router to
advertise ORF send capabilities. To advertise a filter from a sender, you
must create an IP prefix list for the specified BGP peer applied in inbound
derection.
BGP Scaling Configuration
BGP routers connected inside the same AS through BGP belong to an internal BGP session, or IBGP. In order to prevent routing table loops, IBGP speaker does not advertise IBGP-learned routes to other IBGP speaker (Split Horizon mechanism). As such, IBGP requires a full mesh of all peers. For large networks, this quickly becomes unscalable.
There are two ways that help us to mitigate the BGPs full-mesh requirement in a network:
Using BGP route-reflectors
Using BGP confederation
Route Reflector Configuration
Introducing route reflectors removes the need for the full-mesh. When you configure a route reflector you have to tell the router whether the other IBGP router is a client or non-client. A client is an IBGP router that the route reflector will “reflect” routes to, the non-client is just a regular IBGP neighbor. Route reflectors mechanism is described in RFC 4456 and updated by RFC 7606.
Confederation Configuration
A BGP confederation divides our AS into sub-ASes to reduce the number of required IBGP peerings. Within a sub-AS we still require full-mesh IBGP but between these sub-ASes we use something that looks like EBGP but behaves like IBGP (called confederation BGP). Confederation mechanism is described in RFC 5065
This command specifies a BGP confederation identifier. <asn> is the number of the autonomous system that internally includes multiple sub-autonomous systems (a confederation).
Operational Mode Commands
Show
BGP table version is 10, local router ID is 10.0.35.3, vrf id 0
Default local pref 100, local AS 65000
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 198.51.100.0/24 10.0.34.4 0 0 65004 i
*> 203.0.113.0/24 10.0.35.5 0 0 65005 i
Displayed 2 routes and 2 total paths
This command displays information about the particular entry in the BGP routing table.
BGP routing table entry for 198.51.100.0/24
Paths: (1 available, best #1, table default)
Advertised to non peer-group peers:
10.0.13.1 10.0.23.2 10.0.34.4 10.0.35.5
65004
10.0.34.4 from 10.0.34.4 (10.0.34.4)
Origin IGP, metric 0, valid, external, best (First path received)
Last update: Wed Jan 6 12:18:53 2021
This command displays routes that belong to specified BGP communities. Valid value is a community number in the range from 1 to 4294967200, or AA:NN (autonomous system-community number/2-byte number), no-export, local-as, or no-advertise.
This command displays routes that are permitted by the BGP community list.
This command displays BGP routes allowed by the specified AS Path access list.
This command displays BGP routes advertised to a neighbor.
This command displays BGP routes originating from the specified BGP neighbor before inbound policy is applied. To use this command inbound soft reconfiguration must be enabled.
This command displays BGP received-routes that are accepted after filtering.
This command displays dampened routes received from BGP neighbor.
This command displays information about BGP routes whose AS path matches the specified regular expression.
IPv4 Unicast Summary:
BGP router identifier 10.0.35.3, local AS number 65000 vrf-id 0
BGP table version 11
RIB entries 5, using 920 bytes of memory
Peers 4, using 82 KiB of memory
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.0.13.1 4 65000 148 159 0 0 0 02:16:01 0
10.0.23.2 4 65000 136 143 0 0 0 02:13:21 0
10.0.34.4 4 65004 161 163 0 0 0 02:16:01 1
10.0.35.5 4 65005 162 166 0 0 0 02:16:01 1
Total number of neighbors 4
Reset
This command resets BGP connections to the specified neighbor IP address.
With argument soft this command initiates a soft reset. If
you do not specify the in or out options, both
inbound and outbound soft reconfiguration are triggered.
This command uses to clear BGP route dampening information and to unsuppress suppressed routes.
Examples
IPv4 peering
A simple eBGP configuration:
Node 1:
set protocols bgp system-as 65534
set protocols bgp neighbor 192.168.0.2 ebgp-multihop '2'
set protocols bgp neighbor 192.168.0.2 remote-as '65535'
set protocols bgp neighbor 192.168.0.2 update-source '192.168.0.1'
set protocols bgp address-family ipv4-unicast network '172.16.0.0/16'
set protocols bgp parameters router-id '192.168.0.1'
Node 2:
set protocols bgp system-as 65535
set protocols bgp neighbor 192.168.0.1 ebgp-multihop '2'
set protocols bgp neighbor 192.168.0.1 remote-as '65534'
set protocols bgp neighbor 192.168.0.1 update-source '192.168.0.2'
set protocols bgp address-family ipv4-unicast network '172.17.0.0/16'
set protocols bgp parameters router-id '192.168.0.2'
Don’t forget, the CIDR declared in the network statement MUST exist in your routing table (dynamic or static), the best way to make sure that is true is creating a static route:
Node 1:
set protocols static route 172.16.0.0/16 blackhole distance '254'
Node 2:
set protocols static route 172.17.0.0/16 blackhole distance '254'
IPv6 peering
A simple BGP configuration via IPv6.
Node 1:
set protocols bgp system-as 65534
set protocols bgp neighbor 2001:db8::2 ebgp-multihop '2'
set protocols bgp neighbor 2001:db8::2 remote-as '65535'
set protocols bgp neighbor 2001:db8::2 update-source '2001:db8::1'
set protocols bgp neighbor 2001:db8::2 address-family ipv6-unicast
set protocols bgp address-family ipv6-unicast network '2001:db8:1::/48'
set protocols bgp parameters router-id '10.1.1.1'
Node 2:
set protocols bgp system-as 65535
set protocols bgp neighbor 2001:db8::1 ebgp-multihop '2'
set protocols bgp neighbor 2001:db8::1 remote-as '65534'
set protocols bgp neighbor 2001:db8::1 update-source '2001:db8::2'
set protocols bgp neighbor 2001:db8::1 address-family ipv6-unicast
set protocols bgp address-family ipv6-unicast network '2001:db8:2::/48'
set protocols bgp parameters router-id '10.1.1.2'
Don’t forget, the CIDR declared in the network statement MUST exist in your routing table (dynamic or static), the best way to make sure that is true is creating a static route:
Node 1:
set protocols static route6 2001:db8:1::/48 blackhole distance '254'
Node 2:
set protocols static route6 2001:db8:2::/48 blackhole distance '254'
Route Filtering
Route filter can be applied using a route-map:
Node1:
set policy prefix-list AS65535-IN rule 10 action 'permit'
set policy prefix-list AS65535-IN rule 10 prefix '172.16.0.0/16'
set policy prefix-list AS65535-OUT rule 10 action 'deny'
set policy prefix-list AS65535-OUT rule 10 prefix '172.16.0.0/16'
set policy prefix-list6 AS65535-IN rule 10 action 'permit'
set policy prefix-list6 AS65535-IN rule 10 prefix '2001:db8:2::/48'
set policy prefix-list6 AS65535-OUT rule 10 action 'deny'
set policy prefix-list6 AS65535-OUT rule 10 prefix '2001:db8:2::/48'
set policy route-map AS65535-IN rule 10 action 'permit'
set policy route-map AS65535-IN rule 10 match ip address prefix-list 'AS65535-IN'
set policy route-map AS65535-IN rule 10 match ipv6 address prefix-list 'AS65535-IN'
set policy route-map AS65535-IN rule 20 action 'deny'
set policy route-map AS65535-OUT rule 10 action 'deny'
set policy route-map AS65535-OUT rule 10 match ip address prefix-list 'AS65535-OUT'
set policy route-map AS65535-OUT rule 10 match ipv6 address prefix-list 'AS65535-OUT'
set policy route-map AS65535-OUT rule 20 action 'permit'
set protocols bgp system-as 65534
set protocols bgp neighbor 2001:db8::2 address-family ipv4-unicast route-map export 'AS65535-OUT'
set protocols bgp neighbor 2001:db8::2 address-family ipv4-unicast route-map import 'AS65535-IN'
set protocols bgp neighbor 2001:db8::2 address-family ipv6-unicast route-map export 'AS65535-OUT'
set protocols bgp neighbor 2001:db8::2 address-family ipv6-unicast route-map import 'AS65535-IN'
Node2:
set policy prefix-list AS65534-IN rule 10 action 'permit'
set policy prefix-list AS65534-IN rule 10 prefix '172.17.0.0/16'
set policy prefix-list AS65534-OUT rule 10 action 'deny'
set policy prefix-list AS65534-OUT rule 10 prefix '172.17.0.0/16'
set policy prefix-list6 AS65534-IN rule 10 action 'permit'
set policy prefix-list6 AS65534-IN rule 10 prefix '2001:db8:1::/48'
set policy prefix-list6 AS65534-OUT rule 10 action 'deny'
set policy prefix-list6 AS65534-OUT rule 10 prefix '2001:db8:1::/48'
set policy route-map AS65534-IN rule 10 action 'permit'
set policy route-map AS65534-IN rule 10 match ip address prefix-list 'AS65534-IN'
set policy route-map AS65534-IN rule 10 match ipv6 address prefix-list 'AS65534-IN'
set policy route-map AS65534-IN rule 20 action 'deny'
set policy route-map AS65534-OUT rule 10 action 'deny'
set policy route-map AS65534-OUT rule 10 match ip address prefix-list 'AS65534-OUT'
set policy route-map AS65534-OUT rule 10 match ipv6 address prefix-list 'AS65534-OUT'
set policy route-map AS65534-OUT rule 20 action 'permit'
set protocols bgp system-as 65535
set protocols bgp neighbor 2001:db8::1 address-family ipv4-unicast route-map export 'AS65534-OUT'
set protocols bgp neighbor 2001:db8::1 address-family ipv4-unicast route-map import 'AS65534-IN'
set protocols bgp neighbor 2001:db8::1 address-family ipv6-unicast route-map export 'AS65534-OUT'
set protocols bgp neighbor 2001:db8::1 address-family ipv6-unicast route-map import 'AS65534-IN'
We could expand on this and also deny link local and multicast in the rule 20 action deny.