Update-Source

Scenario to verify BGP neighbor update-source functionality. The update-source command specifies which interface’s IP address to use as the source address for BGP sessions. This test uses a loopback/dummy interface as update-source, which is a common pattern for BGP stability - if a physical interface fails but alternative routes exist, the session survives.

Test iBGP - Session establishes without update-source using direct interface

Description

Test to verify that without update-source, BGP uses the outgoing interface IP as the source address. DUT0 peers with DUT1’s directly connected address (10.10.0.200), and DUT1 expects connections from DUT0’s directly connected address (10.10.0.100). Both peers use their physical interface IPs, so the session establishes normally without needing update-source.

Scenario

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 2.2.2.100/32
set interfaces ethernet eth0 address 10.10.0.100/24
set protocols bgp 20 neighbor peer remote-address 10.10.0.200
set protocols bgp 20 neighbor peer remote-as 20
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 10.10.0.200/24
set protocols bgp 20 neighbor peer remote-address 10.10.0.100
set protocols bgp 20 neighbor peer remote-as 20
set protocols bgp 20 redistribute connected
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 3: Run the command protocols bgp show ip summary on DUT0 and check whether the output contains the following tokens:

Established

Attention

Verify BGP session is established using directly connected interface addresses.

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

10.10.0.200.*Established

Attention

Verify that DUT0 local address is from the physical interface (not loopback).

Step 5: Run the command protocols bgp show ip neighbors on DUT0 and check whether the output matches the following regular expressions:

Local host: 10.10.0.100

Show output

BGP neighbor is 10.10.0.200, remote AS 20, local AS 20, internal link
Local Role: undefined
Remote Role: undefined
Hostname: osdx
BGP version 4, remote router ID 10.10.0.200, local router ID 10.10.0.100
BGP state = Established, up for 00:00:05
Last read 00:00:04, Last write 00:00:04
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: 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:          0          0
Updates:                1          3
Keepalives:             1          1
Route Refresh:          0          0
Capability:             0          0
Total:                  4          5

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
Update group 1, subgroup 1
Packet Queue length 0
Community attribute sent to this neighbor(all)
2 accepted, 0 sent prefixes

Connections established 1; dropped 0
Last reset 00:00:08,  No path to specified Neighbor (n/a)
Internal BGP neighbor may be up to 255 hops away.
Local host: 10.10.0.100, Local port: 179
Foreign host: 10.10.0.200, Foreign port: 58638
Nexthop: 10.10.0.100
Nexthop global: fe80::dcad:beff:feef:6c00
Nexthop local: fe80::dcad:beff:feef:6c00
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: 29

Attention

Verify that DUT0 receives route 1.1.1.0/24 from DUT1.

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

1.1.1.0/24.*10.10.0.200

Test iBGP - Neighbor update-source with loopback

Description

Test BGP neighbor update-source with a loopback/dummy interface. DUT0 uses update-source to set its dummy interface (2.2.2.100) as the source address for BGP packets. DUT1 is configured to peer with that loopback IP and has a static route to reach it. The update-source command is necessary here because DUT1 expects connections from 2.2.2.100, not from the physical interface IP. This pattern provides BGP session stability - if the physical link fails but alternative routes exist to the loopback, the session can survive.

Scenario

Note

When using update-source with a loopback, the peer must be configured to expect connections from the loopback IP and must have a route to reach it.

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 2.2.2.100/32
set interfaces ethernet eth0 address 10.10.0.100/24
set protocols bgp 20 neighbor peer remote-address 10.10.0.200
set protocols bgp 20 neighbor peer remote-as 20
set protocols bgp 20 neighbor peer update-source dum0
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 10.10.0.200/24
set protocols bgp 20 neighbor peer remote-address 2.2.2.100
set protocols bgp 20 neighbor peer remote-as 20
set protocols bgp 20 redistribute connected
set protocols static route 2.2.2.0/24 next-hop 10.10.0.100
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 3: Run the command protocols bgp show ip summary on DUT0 and check whether the output contains the following tokens:

Established

Attention

Verify BGP session is established using the loopback address.

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

10.10.0.200.*Established

Attention

Verify that DUT0 local address is from the dummy/loopback interface.

Step 5: Run the command protocols bgp show ip neighbors on DUT0 and check whether the output matches the following regular expressions:

Local host: 2.2.2.100

Show output

BGP neighbor is 10.10.0.200, remote AS 20, local AS 20, internal link
Local Role: undefined
Remote Role: undefined
Hostname: osdx
BGP version 4, remote router ID 10.10.0.200, local router ID 10.10.0.100
BGP state = Established, up for 00:00:05
Last read 00:00:04, Last write 00:00:04
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: 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:          0          0
Updates:                1          3
Keepalives:             1          1
Route Refresh:          0          0
Capability:             0          0
Total:                  4          5

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)
Update source is dum0

For address family: IPv4 Unicast
Update group 1, subgroup 1
Packet Queue length 0
Community attribute sent to this neighbor(all)
2 accepted, 0 sent prefixes

Connections established 1; dropped 0
Last reset 00:00:08,  No path to specified Neighbor (n/a)
Internal BGP neighbor may be up to 255 hops away.
Local host: 2.2.2.100, Local port: 179
Foreign host: 10.10.0.200, Foreign port: 48708
Nexthop: 2.2.2.100
Nexthop global: fe80::54d8:90ff:fe44:bcd
Nexthop local: fe80::54d8:90ff:fe44:bcd
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: 29

Attention

Verify that DUT1 sees DUT0 with the loopback IP as neighbor.

Step 6: Run the command protocols bgp show ip summary on DUT1 and check whether the output matches the following regular expressions:

2.2.2.100.*Established

Attention

Verify that DUT0 receives route 1.1.1.0/24 from DUT1.

Step 7: Run the command protocols bgp show ip on DUT0 and check whether the output matches the following regular expressions:

1.1.1.0/24.*10.10.0.200