BGP Auto-Discovered Neighbors
Understanding BGP Auto-discovered Neighbor
SUMMARY Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses.
To establish a BGP session between routers, you must explicitly configure BGP groups and peers by address. BGP peering sessions require that you identify source and destination IP addresses for endpoints of the TCP communication. Therefore, explicitly configuring these addresses is an obstacle to network scale-out and an opportunity for misconfiguration.
To streamline your BGP configuration, we have removed the need to configure per-peer address from BGP. Use BGP auto-discovered neighbor to configure BGP peering by interface rather than by specifying remote or local neighbor IP addresses. This includes use of implicit or protocol mechanisms to discover the IP addresses for use in the TCP peering sessions.
Peering behavior and address usage must be explicitly configured to avoid peering changes based on interface address changes due to configuration or address validity (for example, IPv6 Duplicate Address Detection (DAD)).
BGP determines the address families to peer over based on the configuration. The peering sessions come up based on availability of the interface addresses for the determined families. The peer link-local address is discovered using IPv6 neighbor discovery (RFC4861) and creates a BGP session toward that neighbor. A link-local address is generated even when IPv6 interfaces have no addresses configured.
You must enable IPv6 neighbor discovery for this feature to work.
Benefits of BGP Auto-discovered Neighbor
-
Simplifies IGP deployment to a single-hop external BGP (EBGP)
-
Configures neighbors by interfaces and interface ranges instead of by IP addresses
-
Minimizes configuration on both sides with dynamic-neighbor groups
Example: Configuring BGP Auto-discovered Neighbor
SUMMARY This example shows how to configure BGP Auto-discovered Neighbor.
Overview
Starting in Junos OS Release 21.1R1, we support BGP auto-discovered neighbors using IPv6 Neighbor Discovery Protocol (ND). This feature allows BGP to create peer neighbor sessions using link-local IPv6 addresses of directly connected neighbor routers. You need not specify remote or local neighbor IP addresses.
Topology
The following figure shows a simplified sample topology.
Requirements
This example uses the following hardware and software components:
MX Series routers
Junos OS Release 21.1R1 or later
Configuration
CLI Quick Configuration
To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.
VM1
set interfaces interface-range tor-to-leaf member ge-0/0/4 set interfaces interface-range tor-to-leaf unit 0 family inet6 set interfaces ge-0/0/4 unit 0 family inet address 192.168.1.1/24 set interfaces lo0 unit 0 family inet address 192.168.30.1/32 set interfaces lo0 unit 0 family inet6 address 2001:db8:70::1/128 set policy-options policy-statement DIRECT-RTS from protocol direct set policy-options policy-statement DIRECT-RTS then accept set policy-options policy-statement lb then load-balance per-packet set policy-options as-list a-list members 1-65535 set routing-options autonomous-system 64500 set routing-options forwarding-table export lb set routing-options forwarding-table ecmp-fast-reroute set protocols router-advertisement interface tor-to-leaf set protocols bgp group autodisc family inet unicast extended-nexthop set protocols bgp group autodisc family inet6 unicast set protocols bgp group autodisc export DIRECT-RTS set protocols bgp group autodisc multipath multiple-as set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface tor-to-leaf set protocols bgp group autodisc peer-as-list a-list set protocols bgp group to-leaf-v4 family inet unicast extended-nexthop set protocols bgp group to-leaf-v4 export DIRECT-RTS set protocols bgp group to-leaf-v4 local-as 64500 set protocols bgp group to-leaf-v4 neighbor 192.168.1.2 peer-as 64496
VM2
set interfaces interface-range tor-to-leaf member ge-0/0/4 set interfaces interface-range tor-to-leaf unit 0 family inet6 set interfaces ge-0/0/4 unit 0 family inet address 192.168.2.1/24 set interfaces lo0 unit 0 family inet address 192.168.30.2/32 set interfaces lo0 unit 0 family inet6 address 2001:db8:60::1/128 set policy-options policy-statement DIRECT-RTS from protocol direct set policy-options policy-statement DIRECT-RTS then accept set policy-options policy-statement lb then load-balance per-packet set policy-options as-list a-list members 1-65535 set routing-options autonomous-system 64501 set routing-options forwarding-table export lb set routing-options forwarding-table ecmp-fast-reroute set protocols router-advertisement interface tor-to-leaf set protocols bgp group autodisc family inet unicast extended-nexthop set protocols bgp group autodisc family inet6 unicast set protocols bgp group autodisc export DIRECT-RTS set protocols bgp group autodisc multipath multiple-as set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface tor-to-leaf set protocols bgp group autodisc peer-as-list a-list set protocols bgp group to-leaf-v4 family inet unicast extended-nexthop set protocols bgp group to-leaf-v4 export DIRECT-RTS set protocols bgp group to-leaf-v4 local-as 64501 set protocols bgp group to-leaf-v4 neighbor 192.168.2.2 peer-as 64497
Leaf 1
set interfaces interface-range to-spine member "ge-0/0/[0-4]" set interfaces interface-range to-spine unit 0 family inet set interfaces interface-range to-spine unit 0 family inet6 set interfaces ge-0/0/4 unit 0 family inet address 192.168.1.2/24 set interfaces lo0 unit 0 family inet address 192.168.10.1/32 set interfaces lo0 unit 0 family inet6 address 2001:db8:90::1/128 set policy-options policy-statement DIRECT-RTS from protocol direct set policy-options policy-statement DIRECT-RTS then accept set policy-options policy-statement lb then load-balance per-packet set policy-options as-list a-list members 1-65535 set routing-options autonomous-system 64496 set routing-options forwarding-table export lb set routing-options forwarding-table ecmp-fast-reroute set protocols router-advertisement interface to-spine max-advertisement-interval 9 set protocols router-advertisement interface to-spine min-advertisement-interval 3 set protocols bgp group autodisc family inet unicast extended-nexthop set protocols bgp group autodisc family inet6 unicast set protocols bgp group autodisc export DIRECT-RTS set protocols bgp group autodisc multipath multiple-as set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface to-spine set protocols bgp group autodisc peer-as-list a-list set protocols bgp group to-crpd-v4 family inet unicast extended-nexthop set protocols bgp group to-crpd-v4 export DIRECT-RTS set protocols bgp group to-crpd-v4 neighbor 192.168.1.1 peer-as 64500
Leaf 2
set interfaces interface-range to-spine member "ge-0/0/[0-4]" set interfaces interface-range to-spine unit 0 family inet set interfaces interface-range to-spine unit 0 family inet6 set interfaces ge-0/0/4 unit 0 family inet address 192.168.2.2/24 set interfaces lo0 unit 0 family inet address 192.168.10.2/32 set interfaces lo0 unit 0 family inet6 address 2001:db8:90::2/128 set policy-options policy-statement DIRECT-RTS from protocol direct set policy-options policy-statement DIRECT-RTS then accept set policy-options policy-statement lb then load-balance per-packet set policy-options as-list a-list members 1-65535 set routing-options autonomous-system 64497 set routing-options forwarding-table export lb set routing-options forwarding-table ecmp-fast-reroute set protocols router-advertisement interface to-spine max-advertisement-interval 9 set protocols router-advertisement interface to-spine min-advertisement-interval 3 set protocols bgp group autodisc family inet unicast extended-nexthop set protocols bgp group autodisc family inet6 unicast set protocols bgp group autodisc export DIRECT-RTS set protocols bgp group autodisc multipath multiple-as set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface to-spine set protocols bgp group autodisc peer-as-list a-list set protocols bgp group to-crpd-v4 family inet unicast extended-nexthop set protocols bgp group to-crpd-v4 export DIRECT-RTS set protocols bgp group to-crpd-v4 neighbor 192.168.2.1 peer-as 64501
Spine 1
set interfaces interface-range to-leaf member "ge-0/0/[0-3]" set interfaces interface-range to-leaf unit 0 family inet set interfaces interface-range to-leaf unit 0 family inet6 set interfaces lo0 unit 0 family inet address 192.168.20.1/32 set interfaces lo0 unit 0 family inet6 address 2001:db8:80::1/128 set policy-options policy-statement DIRECT-RTS from protocol direct set policy-options policy-statement DIRECT-RTS then accept set policy-options policy-statement lb then load-balance per-packet set policy-options as-list a-list members 1-65535 set routing-options autonomous-system 64498 set routing-options forwarding-table export lb set routing-options forwarding-table ecmp-fast-reroute set protocols router-advertisement interface to-leaf max-advertisement-interval 9 set protocols router-advertisement interface to-leaf min-advertisement-interval 3 set protocols bgp group autodisc family inet unicast extended-nexthop set protocols bgp group autodisc family inet6 unicast set protocols bgp group autodisc export DIRECT-RTS set protocols bgp group autodisc multipath multiple-as set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface to-leaf set protocols bgp group autodisc peer-as-list a-list
Spine 2
set interfaces interface-range to-leaf member "ge-0/0/[0-3]" set interfaces interface-range to-leaf unit 0 family inet set interfaces interface-range to-leaf unit 0 family inet6 set interfaces lo0 unit 0 family inet address 192.168.20.2/32 set interfaces lo0 unit 0 family inet6 address 2001:db8:80::2/128 set policy-options policy-statement DIRECT-RTS from protocol direct set policy-options policy-statement DIRECT-RTS then accept set policy-options policy-statement lb then load-balance per-packet set policy-options as-list a-list members 1-65535 set routing-options autonomous-system 64499 set routing-options forwarding-table export lb set routing-options forwarding-table ecmp-fast-reroute set protocols router-advertisement interface to-leaf max-advertisement-interval 9 set protocols router-advertisement interface to-leaf min-advertisement-interval 3 set protocols bgp group autodisc family inet unicast extended-nexthop set protocols bgp group autodisc family inet6 unicast set protocols bgp group autodisc export DIRECT-RTS set protocols bgp group autodisc multipath multiple-as set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface to-leaf set protocols bgp group autodisc peer-as-list a-list
Configuring VM1
To configure BGP auto-discovered neighbor, perform the following steps on VM1:
-
Configure the device interfaces.
user@VM1# set interfaces interface-range tor-to-leaf member ge-0/0/4 user@VM1# set interfaces interface-range tor-to-leaf unit 0 family inet6
-
Create the loopback interface and configure the IP address.
user@VM1# set interfaces lo0 unit 0 family inet address 192.168.30.1/32 user@VM1# set interfaces lo0 unit 0 family inet6 address 2001:db8:70::1/128
-
Enable routing policies.
user@VM1# set policy-options policy-statement DIRECT-RTS from protocol direct user@VM1# set policy-options policy-statement DIRECT-RTS then accept user@VM1# set policy-options policy-statement lb then load-balance per-packet user@VM1# set policy-options as-list a-list members 1-65535
-
Configure the autonomous system (AS) number
user@VM1# set routing-options autonomous-system 64500
-
Apply the per-packet policy to enable load balancing of traffic and ECMP.
user@VM1# set routing-options forwarding-table export lb user@VM1# set routing-options forwarding-table ecmp-fast-reroute
-
Configure BGP to establish internal and external peering sessions.
user@VM1# set protocols bgp group autodisc family inet unicast extended-nexthop user@VM1# set protocols bgp group autodisc family inet6 unicast user@VM1# set protocols bgp group autodisc export DIRECT-RTS user@VM1# set protocols bgp group autodisc multipath multiple-as user@VM1# set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery family inet6 ipv6-nd user@VM1# set protocols bgp group autodisc dynamic-neighbor ndp peer-auto-discovery interface tor-to-leaf user@VM1# set protocols bgp group autodisc peer-as-list a-list user@VM1# set protocols bgp group to-leaf-v4 family inet unicast extended-nexthop user@VM1# set protocols bgp group to-leaf-v4 export DIRECT-RTS user@VM1# set protocols bgp group to-leaf-v4 local-as 5 user@VM1# set protocols bgp group to-leaf-v4 neighbor 192.168.1.2 peer-as 1
-
If you are done configuring the device, commit the configuration.
user@VM1# commit
Results
From configuration mode, confirm your configuration by entering the show interfaces, show protocols, show policy-options, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.
[edit]
user@VM1# show interfaces
interface-range tor-to-leaf {
member ge-0/0/4;
unit 0 {
family inet6;
}
}
ge-0/0/4 {
unit 0 {
family inet {
address 192.168.1.1/24;
}
}
}
lo0 {
unit 0 {
family inet {
address 192.168.30.1/32;
}
family inet6 {
address 2001:db8:70::1/128;
}
}
}
[edit]
user@VM1# show protocols
router-advertisement {
interface tor-to-leaf;
}
bgp {
group autodisc {
family inet {
unicast {
extended-nexthop;
}
}
family inet6 {
unicast;
}
export DIRECT-RTS;
multipath {
multiple-as;
}
dynamic-neighbor ndp {
peer-auto-discovery {
family inet6 {
ipv6-nd;
}
interface tor-to-leaf;
}
}
peer-as-list a-list;
}
group to-leaf-v4 {
family inet {
unicast {
extended-nexthop;
}
}
export DIRECT-RTS;
local-as 64500;
neighbor 192.168.1.2 {
peer-as 64496;
}
}
}
[edit]
user@VM1# show policy-options
policy-statement DIRECT-RTS {
from protocol direct;
then accept;
}
policy-statement lb {
then {
load-balance per-packet;
}
}
as-list a-list members 1-65535;
[edit]
user@VM1# show policy-options
policy-statement DIRECT-RTS {
from protocol direct;
then accept;
}
policy-statement lb {
then {
load-balance per-packet;
}
}
as-list a-list members 1-65535;
[edit]
user@VM1# show routing-options
autonomous-system 64500;
forwarding-table {
export lb;
ecmp-fast-reroute;
}
Verification
Confirm that the configuration is working properly.
Verifying Auto-discovered neighbors
Purpose
Verify the auto-discovered BGP neighbors.
Action
From operational mode, run the show bgp summary
auto-discovered command
On Leaf1
user@Leaf1> show bgp summary auto-discovered
Threading mode: BGP I/O
Default eBGP mode: advertise - accept, receive - accept
Groups: 2 Peers: 5 Down peers: 1
Auto-discovered peers: 4
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0
24 20 0 0 0 0
inet6.0
16 16 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
fe80::5668:a3ff:fe16:1049%ge-0/0/3.0 64499 194 195 0 1 1:25:18 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
fe80::5668:a3ff:fe16:104c%ge-0/0/4.0 64499 193 195 0 1 1:25:18 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
fe80::5668:a3ff:fe16:12c9%ge-0/0/1.0 64498 217 223 0 1 1:35:53 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
fe80::5668:a3ff:fe16:12ce%ge-0/0/2.0 64498 218 223 0 1 1:35:57 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
On Spine1
user@Spine1> show bgp summary auto-discovered
Threading mode: BGP I/O
Default eBGP mode: advertise - accept, receive - accept
Groups: 1 Peers: 4 Down peers: 0
Auto-discovered peers: 4
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0
24 20 0 0 0 0
inet6.0
16 16 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Accepted/Damped...
fe80::5668:a3ff:fe16:2e7%ge-0/0/0.0 64496 245 237 0 0 1:45:19 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
fe80::5668:a3ff:fe16:2f2%ge-0/0/1.0 64496 245 238 0 0 1:45:23 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
fe80::5668:a3ff:fe16:e49%ge-0/0/2.0 64497 245 243 0 0 1:45:19 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
fe80::5668:a3ff:fe16:e59%ge-0/0/3.0 64497 247 248 0 0 1:45:23 Establ
inet.0: 5/6/6/0
inet6.0: 4/4/4/0
Meaning
The output shows the summary of auto-discovered bgp neighbors. You can see the number of auto-discovered peers and its details.
Verifying BGP Auto-discovered Peers
Purpose
Verify the auto-discovered BGP neighbors.
Action
From operational mode, run the show bgp neighbor
auto-discovered command.
On Leaf1
user@Leaf1> show bgp neighbor auto-discovered Peer: fe80::5668:a3ff:fe16:1049%ge-0/0/3.0+65265 AS 64499 Local: fe80::5668:a3ff:fe16:2f6%ge-0/0/3.0+179 AS 64496 Group: autodisc Routing-Instance: master Forwarding routing-instance: master Type: External State: Established Flags: <Sync PeerAsList AutoDiscoveredNdp> Last State: OpenConfirm Last Event: RecvKeepAlive Last Error: None Export: [ DIRECT-RTS ] Options: <AddressFamily Multipath Refresh> Options: <MultipathAs> Options: <GracefulShutdownRcv> Address families configured: inet-unicast inet6-unicast Holdtime: 90 Preference: 170 Graceful Shutdown Receiver local-preference: 0 Number of flaps: 1 Last flap event: RecvNotify Error: 'Cease' Sent: 0 Recv: 1 Peer ID: 128.49.102.24 Local ID: 128.49.102.139 Active Holdtime: 90 Keepalive Interval: 30 Group index: 2 Peer index: 2 SNMP index: 9 I/O Session Thread: bgpio-0 State: Enabled BFD: disabled, down Local Interface: ge-0/0/3.0 NLRI for restart configured on peer: inet-unicast inet6-unicast NLRI advertised by peer: inet-unicast inet6-unicast NLRI for this session: inet-unicast inet6-unicast Peer supports Refresh capability (2) Stale routes from peer are kept for: 300 Peer does not support Restarter functionality Restart flag received from the peer: Notification NLRI that restart is negotiated for: inet-unicast inet6-unicast NLRI of received end-of-rib markers: inet-unicast inet6-unicast NLRI of all end-of-rib markers sent: inet-unicast inet6-unicast ....................
On Spine1
user@Spine1> show bgp neighbor auto-discovered Peer: fe80::5668:a3ff:fe16:2e7%ge-0/0/0.0+60458 AS 64496 Local: fe80::5668:a3ff:fe16:12c9%ge-0/0/0.0+179 AS 64498 Group: autodisc Routing-Instance: master Forwarding routing-instance: master Type: External State: Established Flags: <Sync PeerAsList AutoDiscoveredNdp> Last State: OpenConfirm Last Event: RecvKeepAlive Last Error: None Export: [ DIRECT-RTS ] Options: <AddressFamily Multipath Refresh> Options: <MultipathAs> Options: <GracefulShutdownRcv> Address families configured: inet-unicast inet6-unicast Holdtime: 90 Preference: 170 Graceful Shutdown Receiver local-preference: 0 Number of flaps: 0 Peer ID: 128.49.102.139 Local ID: 128.49.103.129 Active Holdtime: 90 Keepalive Interval: 30 Group index: 1 Peer index: 3 SNMP index: 7 I/O Session Thread: bgpio-0 State: Enabled BFD: disabled, down Local Interface: ge-0/0/0.0 NLRI for restart configured on peer: inet-unicast inet6-unicast NLRI advertised by peer: inet-unicast inet6-unicast NLRI for this session: inet-unicast inet6-unicast Peer supports Refresh capability (2) Stale routes from peer are kept for: 300 Peer does not support Restarter functionality Restart flag received from the peer: Notification NLRI that restart is negotiated for: inet-unicast inet6-unicast NLRI of received end-of-rib markers: inet-unicast inet6-unicast NLRI of all end-of-rib markers sent: inet-unicast inet6-unicast Peer does not support LLGR Restarter functionality Peer supports 4 byte AS extension (peer-as 64496) Peer does not support Addpath NLRI that we support extended nexthop encoding for: inet-unicast NLRI that peer supports extended nexthop encoding for: inet-unicast Table inet.0 Bit: 20000 ....................
Meaning
The output shows information about the auto-discovered BGP neighbors.