Graceful-Restart

Scenario to verify BGP neighbor graceful-restart functionality. Graceful restart allows a BGP router to maintain forwarding state during a restart, minimizing traffic disruption. The helper peer keeps routes from the restarting peer temporarily instead of immediately removing them. This test uses the shutdown command to simulate a session drop.

Test iBGP - Graceful restart with helper

Description

Test BGP graceful-restart functionality. DUT0 is configured in restart mode and DUT1 as helper. When DUT0’s BGP session goes down (via shutdown), DUT1 should keep the routes from DUT0 temporarily (stale) instead of immediately removing them.

Scenario

Note

graceful-restart restart mode: the router can restart and asks peer to keep routes. graceful-restart helper mode: the router helps peers that restart by keeping their routes.

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.10.0.100/24
set protocols bgp 20 neighbor peer graceful-restart restart
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 redistribute connected
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 2: Set the following configuration in DUT1 :

set interfaces ethernet eth0 address 10.10.0.200/24
set protocols bgp 20 neighbor peer graceful-restart helper
set protocols bgp 20 neighbor peer remote-address 10.10.0.100
set protocols bgp 20 neighbor peer remote-as 20
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 between DUT0 and DUT1.

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 DUT1 receives route 1.1.1.0/24 from DUT0.

Step 5: Run the command protocols bgp show ip on DUT1 and check whether the output matches the following regular expressions:

1.1.1.0/24

Attention

Verify graceful-restart is enabled on DUT0.

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

Graceful Restart Capability: advertised and received

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: Restart
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
Configured Selection Deferral Time(sec): 120
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:                3          1
Keepalives:             1          1
Route Refresh:          0          0
Capability:             0          0
Total:                  6          3

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)
0 accepted, 2 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: 44952
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

Note

Shutdown BGP neighbor on DUT0 to simulate a restart scenario.

Step 7: Modify the following configuration lines in DUT0 :

set protocols bgp 20 neighbor peer shutdown

Attention

Verify session is down on DUT0.

Step 8: Run the command protocols bgp show ip summary on DUT0 and check whether the output matches the following regular expressions:

10.10.0.200.*Idle \(Admin\)

Attention

Verify that DUT1 still has the route marked as stale (S flag = graceful restart in progress).

Step 9: Run the command protocols bgp show ip on DUT1 and check whether the output matches the following regular expressions:

S.*1.1.1.0/24

Note

Re-enable the BGP neighbor on DUT0.

Step 10: Modify the following configuration lines in DUT0 :

delete protocols bgp 20 neighbor peer shutdown

Attention

Verify BGP session is re-established.

Step 11: 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 DUT1 route is no longer stale after session recovery (no S flag).

Step 12: Run the command protocols bgp show ip on DUT1 and check whether the output matches the following regular expressions:

[*].*1.1.1.0/24

Test iBGP - Graceful restart disabled

Description

Test BGP behavior when graceful-restart is disabled. When the session goes down, the peer should immediately remove the routes instead of keeping them as stale.

Scenario

Step 1: Set the following configuration in DUT0 :

set interfaces dummy dum0 address 1.1.1.1/24
set interfaces ethernet eth0 address 10.10.0.100/24
set protocols bgp 20 neighbor peer graceful-restart disable
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 redistribute connected
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 2: Set the following configuration in DUT1 :

set interfaces ethernet eth0 address 10.10.0.200/24
set protocols bgp 20 neighbor peer graceful-restart disable
set protocols bgp 20 neighbor peer remote-address 10.10.0.100
set protocols bgp 20 neighbor peer remote-as 20
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 between DUT0 and DUT1.

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 DUT1 receives route 1.1.1.0/24 from DUT0.

Step 5: Run the command protocols bgp show ip on DUT1 and check whether the output matches the following regular expressions:

1.1.1.0/24

Note

Shutdown BGP neighbor on DUT0.

Step 6: Modify the following configuration lines in DUT0 :

set protocols bgp 20 neighbor peer shutdown

Attention

Verify session is down on DUT0.

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

10.10.0.200.*Idle \(Admin\)

Attention

Verify that DUT1 immediately removes the route (no stale, no graceful restart).

Step 8: Run the command protocols bgp show ip on DUT1 and check whether the output does not match the following regular expressions:

1.1.1.0/24