Addpath

Scenario to verify BGP peer-group addpath inheritance. By default, BGP only advertises the single best path for each prefix to its neighbors. The addpath feature allows the router to advertise multiple paths, giving the receiving peer visibility of alternative routes for its own path selection. The addpath-tx-all-paths option advertises all available paths for a prefix to the neighbor. The addpath-tx-bestpath-per-AS option provides a middle ground by advertising only the best path from each originating AS. When configured on a peer-group, all members of the group inherit the addpath behavior.

../../../../_images/addpath1.svg

Test eBGP - Peer-group addpath modes

Description

Test addpath modes on a peer-group: without addpath (baseline, 1 path), with addpath-tx-all-paths (2 paths), and with addpath-tx-bestpath-per-AS (2 paths).

Scenario

Example 1

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.0.0.1/24
set interfaces ethernet eth1 address 10.0.1.1/24
set protocols bgp 100 neighbor receiver peer-group RECEIVERS
set protocols bgp 100 neighbor receiver remote-address 10.0.1.2
set protocols bgp 100 neighbor sender remote-address 10.0.0.2
set protocols bgp 100 neighbor sender remote-as 200
set protocols bgp 100 neighbor sender route-map import PERMIT
set protocols bgp 100 peer-group RECEIVERS remote-as 300
set protocols bgp 100 peer-group RECEIVERS route-map export PERMIT
set protocols bgp 100 redistribute connected
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 2: Set the following configuration in DUT1 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.0.0.2/24
set protocols bgp 200 neighbor peer remote-address 10.0.0.1
set protocols bgp 200 neighbor peer remote-as 100
set protocols bgp 200 neighbor peer route-map export PERMIT
set protocols bgp 200 redistribute connected
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 3: Set the following configuration in DUT2 :

set interfaces ethernet eth1 address 10.0.1.2/24
set protocols bgp 300 neighbor peer remote-address 10.0.1.1
set protocols bgp 300 neighbor peer remote-as 100
set protocols bgp 300 neighbor peer route-map import PERMIT
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Attention

Verify eBGP sessions establish.

Step 4: Run the command protocols bgp show ip summary on DUT0 and check whether the output matches the following regular expressions:

10.0.1.2.*Established[\s\S]*10.0.0.2.*Established
Show output
IPv4 Unicast Summary:
BGP router identifier 10.0.1.1, local AS number 100 VRF default vrf-id 0
BGP table version 5
RIB entries 5, using 760 bytes of memory
Peers 2, using 47 KiB of memory
Peer groups 1, using 64 bytes of memory

Neighbor        LocalAddr       V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down        State   PfxRcd   PfxSnt Desc
10.0.1.2        10.0.1.1        4        300         4         5        0    0    0 00:00:00  Established (Policy)        0 N/A
10.0.0.2        10.0.0.1        4        200         5         3        5    0    0 00:00:02  Established        2 (Policy) N/A

Total number of neighbors 2

Attention

Verify DUT2 receives 1 path(s) for 1.1.1.0/24.

Step 5: Run the command protocols bgp show ip 1.1.1.0/24 on DUT2 and check whether the output matches the following regular expressions:

Paths:.*1 available
Show output
BGP routing table entry for 1.1.1.0/24, version 1
Paths: (1 available, best #1, table default)
  Not advertised to any peer
  100
    10.0.1.1 from 10.0.1.1 (10.0.1.1)
      Origin incomplete, metric 0, valid, external, best (First path received)
      Last update: Tue May 19 14:16:59 2026

Example 2

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.0.0.1/24
set interfaces ethernet eth1 address 10.0.1.1/24
set protocols bgp 100 neighbor receiver peer-group RECEIVERS
set protocols bgp 100 neighbor receiver remote-address 10.0.1.2
set protocols bgp 100 neighbor sender remote-address 10.0.0.2
set protocols bgp 100 neighbor sender remote-as 200
set protocols bgp 100 neighbor sender route-map import PERMIT
set protocols bgp 100 peer-group RECEIVERS addpath-tx-all-paths
set protocols bgp 100 peer-group RECEIVERS remote-as 300
set protocols bgp 100 peer-group RECEIVERS route-map export PERMIT
set protocols bgp 100 redistribute connected
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 2: Set the following configuration in DUT1 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.0.0.2/24
set protocols bgp 200 neighbor peer remote-address 10.0.0.1
set protocols bgp 200 neighbor peer remote-as 100
set protocols bgp 200 neighbor peer route-map export PERMIT
set protocols bgp 200 redistribute connected
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 3: Set the following configuration in DUT2 :

set interfaces ethernet eth1 address 10.0.1.2/24
set protocols bgp 300 neighbor peer remote-address 10.0.1.1
set protocols bgp 300 neighbor peer remote-as 100
set protocols bgp 300 neighbor peer route-map import PERMIT
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Attention

Verify eBGP sessions establish.

Step 4: Run the command protocols bgp show ip summary on DUT0 and check whether the output matches the following regular expressions:

10.0.1.2.*Established[\s\S]*10.0.0.2.*Established
Show output
IPv4 Unicast Summary:
BGP router identifier 10.0.1.1, local AS number 100 VRF default vrf-id 0
BGP table version 7
RIB entries 5, using 760 bytes of memory
Peers 2, using 47 KiB of memory
Peer groups 1, using 64 bytes of memory

Neighbor        LocalAddr       V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down        State   PfxRcd   PfxSnt Desc
10.0.1.2        10.0.1.1        4        300         4         4        0    0    0 00:00:01  Established (Policy)        0 N/A
10.0.0.2        10.0.0.1        4        200         5         3        7    0    0 00:00:02  Established        2 (Policy) N/A

Total number of neighbors 2

Attention

Verify DUT2 receives 2 path(s) for 1.1.1.0/24.

Step 5: Run the command protocols bgp show ip 1.1.1.0/24 on DUT2 and check whether the output matches the following regular expressions:

Paths:.*2 available
Show output
BGP routing table entry for 1.1.1.0/24, version 1
Paths: (2 available, best #1, table default)
  Not advertised to any peer
  100
    10.0.1.1 from 10.0.1.1 (10.0.1.1)
      Origin incomplete, metric 0, valid, external, best (AS Path)
      AddPath ID: RX 2, TX-All 0 TX-Best-Per-AS 0 TX-Best-Selected 0
      Last update: Tue May 19 14:17:10 2026
  100 200
    10.0.1.1 from 10.0.1.1 (10.0.1.1)
      Origin incomplete, valid, external
      AddPath ID: RX 5, TX-All 0 TX-Best-Per-AS 0 TX-Best-Selected 0
      Last update: Tue May 19 14:17:10 2026

Attention

Verify addpath TX is advertised on the neighbor.

Step 6: Run the command protocols bgp show ip neighbors neighbor receiver on DUT0 and check whether the output matches the following regular expressions:

IPv4 Unicast: TX advertised
Show output
BGP neighbor is 10.0.1.2, remote AS 300, local AS 100, external link
  Local Role: undefined
  Remote Role: undefined
Hostname: osdx
 Member of peer-group RECEIVERS for session parameters
  BGP version 4, remote router ID 10.0.1.2, local router ID 10.0.1.1
  BGP state = Established, up for 00:00:03
  Last read 00:00:01, Last write 00:00:01
  Hold time is 90 seconds, keepalive interval is 30 seconds
  Configured hold time is 90 seconds, keepalive interval is 30 seconds
  Configured tcp-mss is 0, synced tcp-mss is 1448
  Configured conditional advertisements interval is 60 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: TX advertised
      IPv4 Unicast: RX advertised and received
    Paths-Limit:
      IPv4 Unicast: advertised (0) and received (0)
    Long-lived Graceful Restart: advertised and received
      Address families by peer:
    Route refresh: advertised and received
    Enhanced Route Refresh: advertised and received
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: osdx,domain name: n/a) received (name: osdx,domain name: n/a)
    Version Capability: not advertised not received
    Link-Local Next Hop Capability: not advertised not received
    Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
            Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Peer has restarted (R-bit is set)
      Peer has restarted (N-bit is set)
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv4 Unicast
    End-of-RIB received: IPv4 Unicast
    Local GR Mode: Helper*
    Remote GR Mode: Helper

    R bit: True
    N bit: True
    Timers:
      Configured Restart Time(sec): 120
      Received Restart Time(sec): 120
      Configured LLGR Stale Path Time(sec): 0
    IPv4 Unicast:
      F bit: False
      End-of-RIB sent: Yes
      End-of-RIB sent after update: Yes
      End-of-RIB received: Yes
      Timers:
        Configured Stale Path Time(sec): 360
        LLGR Stale Path Time(sec): 0
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  2          1
    Notifications:          1          2
    Updates:                9          1
    Keepalives:             1          1
    Route Refresh:          2          1
    Capability:             0          0
    Total:                 15          6

  Prefix statistics:
    Inbound filtered: 0
    AS-PATH loop: 0
    Originator loop: 0
    Cluster loop: 0
    Invalid next-hop: 0
    Withdrawn: 0
    Attributes discarded: 0

  Minimum time between advertisement runs is 0 seconds
  Update delay timer is 0 seconds (remaining: 0)

 For address family: IPv4 Unicast
  RECEIVERS peer-group member
  Update group 2, subgroup 2
  Packet Queue length 0
  Advertise all paths via addpath
  Community attribute sent to this neighbor(all)
  Outbound path policy configured
  Route map for outgoing advertisements is *PERMIT
  Inbound updates discarded due to missing policy
  0 accepted, 5 sent prefixes

  Connections established 1; dropped 0
  Last reset 00:00:06,  Notification sent (Neighbor Events Error/Receive Unexpected Message in OpenSent State)
  External BGP neighbor may be up to 1 hops away.
Local host: 10.0.1.1, Local port: 179
Foreign host: 10.0.1.2, Foreign port: 58002
Nexthop: 10.0.1.1
Nexthop global: fe80::dcad:beff:feef:6c01
Nexthop local: fe80::dcad:beff:feef:6c01
BGP connection: shared network
BGP Connect Retry Timer in Seconds: 30
Estimated round trip time: 0 ms
Read thread: on  Write thread: on  FD used: 31

Example 3

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.0.0.1/24
set interfaces ethernet eth1 address 10.0.1.1/24
set protocols bgp 100 neighbor receiver peer-group RECEIVERS
set protocols bgp 100 neighbor receiver remote-address 10.0.1.2
set protocols bgp 100 neighbor sender remote-address 10.0.0.2
set protocols bgp 100 neighbor sender remote-as 200
set protocols bgp 100 neighbor sender route-map import PERMIT
set protocols bgp 100 peer-group RECEIVERS addpath-tx-bestpath-per-AS
set protocols bgp 100 peer-group RECEIVERS remote-as 300
set protocols bgp 100 peer-group RECEIVERS route-map export PERMIT
set protocols bgp 100 redistribute connected
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 2: Set the following configuration in DUT1 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.0.0.2/24
set protocols bgp 200 neighbor peer remote-address 10.0.0.1
set protocols bgp 200 neighbor peer remote-as 100
set protocols bgp 200 neighbor peer route-map export PERMIT
set protocols bgp 200 redistribute connected
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 3: Set the following configuration in DUT2 :

set interfaces ethernet eth1 address 10.0.1.2/24
set protocols bgp 300 neighbor peer remote-address 10.0.1.1
set protocols bgp 300 neighbor peer remote-as 100
set protocols bgp 300 neighbor peer route-map import PERMIT
set protocols route-map PERMIT rule 1 action permit
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Attention

Verify eBGP sessions establish.

Step 4: Run the command protocols bgp show ip summary on DUT0 and check whether the output matches the following regular expressions:

10.0.1.2.*Established[\s\S]*10.0.0.2.*Established
Show output
IPv4 Unicast Summary:
BGP router identifier 10.0.1.1, local AS number 100 VRF default vrf-id 0
BGP table version 7
RIB entries 5, using 760 bytes of memory
Peers 2, using 47 KiB of memory
Peer groups 1, using 64 bytes of memory

Neighbor        LocalAddr       V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down        State   PfxRcd   PfxSnt Desc
10.0.1.2        10.0.1.1        4        300         2         4        0    0    0 00:00:01  Established (Policy)        0 N/A
10.0.0.2        10.0.0.1        4        200         5         3        7    0    0 00:00:02  Established        2 (Policy) N/A

Total number of neighbors 2

Attention

Verify DUT2 receives 2 path(s) for 1.1.1.0/24.

Step 5: Run the command protocols bgp show ip 1.1.1.0/24 on DUT2 and check whether the output matches the following regular expressions:

Paths:.*2 available
Show output
BGP routing table entry for 1.1.1.0/24, version 1
Paths: (2 available, best #1, table default)
  Not advertised to any peer
  100
    10.0.1.1 from 10.0.1.1 (10.0.1.1)
      Origin incomplete, metric 0, valid, external, best (AS Path)
      AddPath ID: RX 2, TX-All 0 TX-Best-Per-AS 0 TX-Best-Selected 0
      Last update: Tue May 19 14:17:20 2026
  100 200
    10.0.1.1 from 10.0.1.1 (10.0.1.1)
      Origin incomplete, valid, external
      AddPath ID: RX 5, TX-All 0 TX-Best-Per-AS 0 TX-Best-Selected 0
      Last update: Tue May 19 14:17:20 2026

Attention

Verify addpath TX is advertised on the neighbor.

Step 6: Run the command protocols bgp show ip neighbors neighbor receiver on DUT0 and check whether the output matches the following regular expressions:

IPv4 Unicast: TX advertised
Show output
BGP neighbor is 10.0.1.2, remote AS 300, local AS 100, external link
  Local Role: undefined
  Remote Role: undefined
Hostname: osdx
 Member of peer-group RECEIVERS for session parameters
  BGP version 4, remote router ID 10.0.1.2, local router ID 10.0.1.1
  BGP state = Established, up for 00:00:03
  Last read 00:00:01, Last write 00:00:01
  Hold time is 90 seconds, keepalive interval is 30 seconds
  Configured hold time is 90 seconds, keepalive interval is 30 seconds
  Configured tcp-mss is 0, synced tcp-mss is 1448
  Configured conditional advertisements interval is 60 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: TX advertised
      IPv4 Unicast: RX advertised and received
    Paths-Limit:
      IPv4 Unicast: advertised (0) and received (0)
    Long-lived Graceful Restart: advertised and received
      Address families by peer:
    Route refresh: advertised and received
    Enhanced Route Refresh: advertised and received
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: osdx,domain name: n/a) received (name: osdx,domain name: n/a)
    Version Capability: not advertised not received
    Link-Local Next Hop Capability: not advertised not received
    Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
            Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Peer has restarted (R-bit is set)
      Peer has restarted (N-bit is set)
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv4 Unicast
    End-of-RIB received: IPv4 Unicast
    Local GR Mode: Helper*
    Remote GR Mode: Helper

    R bit: True
    N bit: True
    Timers:
      Configured Restart Time(sec): 120
      Received Restart Time(sec): 120
      Configured LLGR Stale Path Time(sec): 0
    IPv4 Unicast:
      F bit: False
      End-of-RIB sent: Yes
      End-of-RIB sent after update: Yes
      End-of-RIB received: Yes
      Timers:
        Configured Stale Path Time(sec): 360
        LLGR Stale Path Time(sec): 0
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  2          1
    Notifications:          1          0
    Updates:                9          1
    Keepalives:             1          1
    Route Refresh:          2          1
    Capability:             0          0
    Total:                 15          4

  Prefix statistics:
    Inbound filtered: 0
    AS-PATH loop: 0
    Originator loop: 0
    Cluster loop: 0
    Invalid next-hop: 0
    Withdrawn: 0
    Attributes discarded: 0

  Minimum time between advertisement runs is 0 seconds
  Update delay timer is 0 seconds (remaining: 0)

 For address family: IPv4 Unicast
  RECEIVERS peer-group member
  Update group 2, subgroup 2
  Packet Queue length 0
  Advertise bestpath per AS via addpath
  Community attribute sent to this neighbor(all)
  Outbound path policy configured
  Route map for outgoing advertisements is *PERMIT
  Inbound updates discarded due to missing policy
  0 accepted, 5 sent prefixes

  Connections established 1; dropped 0
  Last reset 00:00:06,  Cease: connection collision (n/a)
  External BGP neighbor may be up to 1 hops away.
Local host: 10.0.1.1, Local port: 179
Foreign host: 10.0.1.2, Foreign port: 36928
Nexthop: 10.0.1.1
Nexthop global: fe80::dcad:beff:feef:6c01
Nexthop local: fe80::dcad:beff:feef:6c01
BGP connection: shared network
BGP Connect Retry Timer in Seconds: 30
Estimated round trip time: 0 ms
Read thread: on  Write thread: on  FD used: 31